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Over the last two years there has been an evolution in the way that soil nutrient mapping is carried out. This has been driven by the launch of TerraMap by Hutchinsons in 2019. Terramap came at the perfect timing for farmers looking for that next level of accuracy in understanding their soils in order to reap the most benefit for their crops through nutrient mapping and soil conductivity scans.

TerraMap uses gamma-ray radiation technology to deliver resolutions of over 800 points/ha, providing high definition mapping of all common nutrient properties, pH (e.g. % clay, % sand, % silt), soil texture, organic matter and CEC as well as elevation and plant available water. The results from TerraMap are used to create maps within the Omnia precision farming system which can then be overlaid with additional field information such as black-grass, yields and so on, to create the most accurate, consistent and detailed variable rate plans.

The infield process of collecting the data is carried out in 2 very simple steps; scanning by driving a light weight all terrain vehicle fitted with the sensor over a field, and then taking soil samples to allow for each scan to be used to create the individual map layers.

Manufactured by Canadian company SoilOptix, TerraMap’s scanning technology is based on a scaleddown version of airborne sensors that originates in mineral prospecting, and has been used in other countries successfully. The TerraMap sensor is noncontact and pre-calibrated upon manufacturing. It’s an entirely passive sensor. The standard field practise is the scanner is mounted roughly 600-700mm above the ground and the vehicle is driven around 10-12 mph and at 12m swath widths. The sensor is measuring gamma radiation that is being naturally emitted form the soil. Specifically it is measuring Caesium -137,Uranium-238,Thorium-232 & Potassium-40.

Traditional zonal and grid soil sampling, do not by their sheer methodology provide the level of accuracy that TerraMap offers. With the grid system you create a 100x100m grid across the field, taking samples at each point. A map is then generated that extrapolates properties between the data points.  

A zonal system uses an electro-magnetic (EMI) or conductivity scanner to assess soil properties into zones of similar character. Samples are then drawn from within each zone.

The resolution isn’t good with the grid system – the way the smoothing is carried out by the software between data points can be quite crude. The problem with EMI scanning is repeatability – it’s massively affected by soil moisture, so the picture you get of your soil in Sept can be completely different to a scan taken in April. The zonal sampling resolution also tends to be poor – on average one sample represents 2.5ha. As it’s an entirely passive sensor, you can travel from harvest through until March without disturbing an autumnsown crop. It picks up the unique radioactive signature emitted by the soil that’s influenced by its nutrient and mineral content. That signature can be translated back to the core properties.

Just like EMI scanning, the sensor has to be groundtruthed, so soil samples are taken within each field to help the algorithms align the radioactive signature to the actual soil properties. But unlike EMI, that signature remains the same and unique to the point in the field, regardless of moisture, temperature, tillage state or crop cover. Repeatability is one of the key aspects we tested before we launched TerraMap. So several fields were scanned just after harvest when they were dry and in stubble, and were re-scanned as soon as they were fit to travel in early spring. The results are virtually identical – we have real confidence the scanner is measuring something repeatable.

It’s also a one-pass system. Just like an EMI scan, the field is travelled in 12m bouts. The initial scan gives you a map of the raw data points that are displayed on a tablet in the cab. But unlike EMI, the on-board software then uses that information to highlight points within the field to return to for detailed analysis. Before leaving the field, the sensor is returned to a number of pre-defined sampling points. At these points, the spectrometer picks up a more detailed signature and we take a representative soil sample for later analysis.

Terramap is available at two service levels: standard will deliver ten map layers to the grower, directly replacing other soil services currently available. This brings in sand, silt and clay content, giving individual layers of percentage content, as well as a texture map, calculated using the industry-standard soil texture classification.

For Omnia users, it will be the soil texture layer that’s used in combination with seedbed condition, weed and slug pressure to generate a variable rate drilling plan. 

In addition, phosphate, potash and magnesium index maps are returned, along with pH, while an elevation map is also generated. The nutrient and pH layers will directly inform variable rate application maps. Premium service provides information or layers that you don’t get from a standard precision soilsampling service such as levels of the nutrients calcium, sodium, sulphur, manganese, boron, copper, zinc, molybdenum and iron. It’s seen as unlikely that growers will use the maps to variably apply micronutrients. More likely, the information will be used with tissue testing, for example, to identify potential areas of deficiency and to target areas for further investigation.

Organic matter levels and cation exchange capacity (CEC) are two further layers of “good background information” returned by Terramap. Again it’s unlikely growers will use the information to directly spatially apply inputs, although it may indicate areas that warrant further investigation. The final layer is plant-available water based on clay, silt and organic matter content. In the first instance, this could help modify irrigation scheduling, but we believe the information can be used to tailor agronomy closer to crop potential, spatially enhancing overall performance.

The value in the maps may come through the barometer they offer on general soil health, informing how to build resilience into the arable system, and as a basis for applying for future subsidy payments linked to provision of public goods.

TerraMap Carbon

This spring has seen a further exciting development in TerraMap- the ability to provide the most accurate baseline measurement of both organic and active carbon in the soil and is now available to UK farmers. Despite growers coming under increasing pressure to look at their carbon footprint in response to the NFU’s commitment for UK farming to achieve Carbon net zero by 2040 – until now there has been no accurate means of measuring carbon in the soil – and unless you can measure carbon there is no way it can be managed.

The pressure to manage carbon is only going to become greater as other industries are already showing positive change. As an industry UK Farming plc is in a unique and enviable position as farming activities can make positive changes to carbon, which most other industries are not able to do. This challenge comes at a time when the arable industry is facing great change in the light of the loss of basic farm payment, and many growers may well be questioning the importance or relevance of carbon management as potential profit margins are threatened.

We need to move away from seeing carbon footprinting as a burden or simply a tick-box exercise and see that this is beneficial, as a proxy measurement for efficiency and profitability of a farm as well as simply a measure of waste.

So it’s clear that there are benefits such as lower input costs to having a negative carbon balance before even getting to the Carbon bit. A reduced carbon footprint can only be achieved through more efficient fertilisers, different technologies, better soil carbon management or considering the energy used in storage, so it’s a win– win on all levels. In light of these challenges, we have been investing heavily in developing services and technologies that can be utilised at farm level to allow growers to work towards these goals- and the development of Terramap carbon is an exciting and unique development that reflects this approach.

Terramap Carbon is available through the standard or premium service as is the case for soils nutrient scanning. The standard service now also includes total organic carbon in terms of percentage carbon and tonnes/ha whilst the premium service also offers both total organic and active carbon percentage and tonnes/ ha – that is the percentage of carbon that’s active in the soil. Once I have the carbon measurements what can I do with them to achieve any of the potential benefits we have outlined? This is one of the most common questions with regards to carbon management. Nick Wilson of Hundayfield Farm just outside York is the host of the Hutchinsons Helix North Farm, one of the Helix Farms network where Terramap Carbon has been trialled and tested. 

His farm consists of 260ha of mainly arable cropping, with land let out for potatoes and winter sheep grazing on stubble turnips. There is also bed & breakfast cattle which utilise the farm buildings and some of the permanent grass in the rotation. For Nick and his agronomist Sam Hugill, carbon is just a part of the whole farm system, but both believe that it is useful to obtain a baseline measurement now, so that they have a baseline figure to work from going forward.

The results of the Terramap Carbon scanning showed up large differences in the carbon balance between the arable fields and permanent pasture, as you would expect. The average across the arable fields was about 30t/ha of organic carbon and it was almost double that for the permanent pasture. Having a baseline measurement means that Nick can look not just how to manage processes to build carbon on the arable fields up to the levels of that of the pasture, but also to prevent any unnecessary losses of carbon. For example looking at the impact of root crops on carbon or using cover cropping to prevent having any bare land over winter and reducing loss this way.

The carbon management tool allows users to look at these scenario’s using real and accurate measurements and then quantify the impact on carbon. After all as Lord Kelvin, physicist and engineer said: “When you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind.”

In the drylands of Southwestern Australia Ian and Dianne Haggerty are using the concepts of “Natural Intelligence Farming” to build a regenerative enterprise focused on zero tillage, livestock integration and biologically sourced inputs that boost their soil resources and profitability. Ian and Dianne Haggerty are using the concepts of “Natural Intelligence Farming” to build a regenerative enterprise focused on zero tillage, livestock integration and biologically sourced inputs that boost their soil resources and profitability.

Written by John Dobberstein, No-Till Farmer Magazine, USA

Married and both raised in farming families, Ian and Dianne Haggerty were shocked when they sought advice from a farm advisor on managing their fledgling operation in the drylands of southwestern Australia. After looking at their farm size and financial capital, the advisor told them they should get out of farming because they didn’t have “a hope in heck” of surviving. “Fortunately, Ian and I are both pretty stubborn customers and we just took that as a bit of a challenge,” Dianne says, lamenting that her father was a successful conventional farmer. “We didn’t have any room for error, so we had to start to look at things in a different way. At that point in time, using better and different types of machinery wasn’t going to be the answer.”

Rather than internalizing the advisor’s stinging advice, Ian and Dianne researched biological farming methods and have pushed through early challenges to grow their operation and take excess costs and waste out of the system. The Haggertys now no-till cereal grains and multispecies hay or fodder crops and raise specially bred sheep for wool and premium-grade fat lambs. Over time, their 1,600-acre operation has grown to nearly 65,000 acres as they’ve patched together leases and shares and some purchases later on. They’ve actually covered close to 185,000 acres in the country’s central wheatbelt, many parcels having different terrains, soils and rainfall zones.

They describe their approach to notilling as “Natural Intelligence Farming” — which means harnessing dynamic, natural relationships that exist between all the organisms in the ecosystem and the environment itself — particularly the soil. “Really, it’s minimizing our interference as humans,” Dianne told attendees of the No-till on the Plains Winter Conference in early 2020. “We don’t have to actually have an answer all the time. We trust the natural processes and just do our best to enable them to occur.”

Starting from Nothing

Their two main farming bases are at Mollerin and at Wyalkatchem, where the original farm is located. Precipitation is fleeting: During the 1990s, Dianne says, it wasn’t unusual to see 12-13 inches of rain annually, but lately precipitation has been 20-30% lower, equating to 8-9 inches of rain per annum, and at times as low as 5-6 inches. The Haggertys started farming in 1994 although they didn’t inherit any land, which is unusual in western Australia. They didn’t have any money for machinery at that point, but were able to buy about 300 breeding ewes and a piece of land. They borrowed machinery from Dianne’s parents in exchange for Ian doing some seasonal work.

After years of conventional farming, the Haggertys realized their farm was vulnerable to dry seasons. Input costs were steadily increasing without increases in productivity, and even though soil tests showed their soil had adequate nutrient levels, tissue tests showed nutrients weren’t getting to the plants. Hardpans in their soils were also restricting root growth. There are other challenges as well: Saline Soils. Many fields have had salinity issues that have impacted crop and livestock production. Poor Policy. In the early days of farming, the Australian government encouraged the clearing of large tracts of land for farm production. “Unfortunately, that’s had a really severe impact on the whole ecosystem and environment in western Australia,” Dianne says.

Low Organic Matter. In some of the farms they’ve taken on, the Haggertys have found paddocks with no cover at all and very low organic matter — at times as low as 0.15%.

But those challenges, Dianne notes, have taught them to pay attention to how different soil types respond to different cropping approaches and how the livestock in particular respond. “We realized pretty quickly that we had to be fairly resilient, not only in our thinking but also in how we set up our farms so that we could try and overcome a lot of the risks and the challenges,” she says. So they started researching biologically based farming systems to increase their soil’s microbial population, nutrient availability and moisture-holding capacity.

They gained a sense of direction when soil health expert Elaine Ingham and health professional Arden Anderson visited Perth — about 150 miles from their farm — for a 4-day workshop. Ingham emphasized nutrient cycling and water-holding capacity and rebuilding soil structure. Anderson talked about producing the highest quality food possible to restore human health for people in their food chain. They also learned about free-choice mineral systems and livestock integration from south Australian consultant Jane Slattery.

“There are lots of minerals livestock could go and access at their own choice. It wasn’t all premixed and they could select what was needed from different paddocks as required,” Dianne explains.  

“By doing that we’re able to stop drenching the animals and feeding any grain supplements to them, which has had a big impact. Free choice mineral supplements have not been required now since 2006, as epigenetic progress of self-replacing livestock, landscape management and microbiome development has enabled this.”

Making Changes

The Haggertys made a number of changes to their management that they believe contributed to economic and production success:

• Reducing Chemicals. One of biggest changes the Haggertys made was reducing their use of synthetic fertilizers and eliminating fungicides and insecticides. They turned to new technologies that allowed them to apply “worm juice” and compost extract as a way to fertilize crops and improve soil health.

In many cases crops between the two systems were similar but those fertilized with the all-natural products had different rhizosheath development.

• Integrating Livestock. Dianne says working with self-replacing livestock on the farm has made perhaps the most significant impact.

When grain is harvested, the stubble in their high-microbial environment provides nutritious grazing fodder for the sheep. The stubble is eventually trampled and broken down by fungi to add to the organic carbon in the soil. Sheep are shorn every 8 months and produce lambs at a rate between 90% and 150% per annum. By not using drenches or feeding grain to the animals and being able to provide a biodiverse food source for the diet, “the animals have been able to optimize their gut microbiome development and that has really contributed significantly to the farm progression,” Dianne says.  

“What we’ve been able to rely upon is that innate wisdom of those animals, that they know when their health is at a good level. They are able to then smell out those nutrients and things that they require in different plants and also through their learned behavior, if those plants are available. This opportunity for diverse self-selection enables the sheep to optimize conditions in their rumen for appropriate microbiome function. “Of course, if I’ve got a restricted diet with only grass and clover or something, they have only got a couple of choices so there’s not a lot of opportunity. But if they’ve got access to natural bushland or a lot of different plants integrated throughout their paddocks, then they can do that good balancing on their own.”

• Cover Crops. The Haggertys are currently seeding 5,000-7,000 acres per year of cover crops for hay or fodder, mostly in the fall and mainly a mix of cereal grains and a few legumes. Dianne says summer native actives are self-generating over large areas and are bulked up with volunteer pastures.

About 26-30 different species are being used over each year and some of the covers are being grazed.

• Self-Replacing Livestock. Having selfreplacing livestock has been key as well. Research has shown that a lamb inside its mother’s uterus actually receives a lot of information and feeding preferences can be picked up by the lamb before it’s even born, Dianne says.

For example, if the mother’s been eating saltbush or something like that while it’s pregnant, when the lamb is born it can actually tolerate those foodstuffs a lot better than a lamb that wasn’t. “The lamb alongside its mother can learn what plants are most suitable to eat as well. That capacity of having that mother/baby unit for progression is really integral.” 

Prior to reestablishing microbiome integrity in the sheep when they were still requiring drenching and receiving grain supplementation their manure piles were larger, but they’re now half to three-quarters the size with a more diverse feed source that includes native vegetation. Pasture quality is vastly more nutrient dense and diverse: it’s not uncommon to have brix levels in pasture plants at 15- 20 in winter and over 30 in early spring, she notes. And due to the higher-quality diet, the animals don’t have to graze as long or overeat to get what they need, meaning their energy requirements are lower, she says.

“Something else that we’ve noticed, even in our really hot, dry environments, is that over the winter/spring period the animals have become very water efficient,” Dianne says. “There’s been times in a winter and spring period where they haven’t gone to the water trough for 6 months. It shows that their digestive system is very water and food efficient.”

• Liquid Carbon. After working with Ingham in 2006, the Haggertys started with using vermi-liquid and composts in their farming system.

In the Ingham course, Dianne sat next to Rachelle Armstrong, whose father had set up a massive vermiculture farm and they sold a worm liquid concentrate which made it possible to make adoption of an injection system with the liquid a priority. They learned from Dr. Christine Jones the concept of providing a “liquid carbon pathway” so carbon could find its way deeper into the soil profile to help free up the soil’s productivity. Getting carbon established with residue mulch was proving tough due to the lack of rain and establishing ground cover.

“Christine talked a lot about the importance of that appropriate rhizosheath and that microbial bridge between the plant and the soil so that liquid carbon pathway could actually do something,” Dianne says.

They now use a combination of compost extract and worm liquid on foliar post-emergent following broadleaf herbicides if required, using 13 ounces an acre of worm liquid and up to 10 gallons an acre of compost extract. They also do use some plant foods with humics or fulvics at times, and may come back with a second foliar spray if there’s good yield potential, a higher rainfall year or some other restraint to plants identified. The liquids are not only applied at planting but as a foliar to assist crops with pushing roots into compacted acidic or saline soils. This is done, Dianne says, to boost microbial activity and micronutrient availability.  

The Haggertys have a compost extractor from Midwest Biosystems on their farm that creates the liquid. It used to produce about 1,000 liters every 20 minutes, or 20,000 liters in a day, but they could only apply 1-2 gallons an acre. But in 2019, Ian built a 5,800-gallon tank that allows them to apply 1,000 liters in one pass. The tank has a large impeller inside and hoses on the bottom that pumps air through the liquid. The Haggertys own a 60-foot John Deere disc seeder, 50-foot Morris Industries C2 Contour drill with knife points and a 70-foot Morris Quantum air drill with knife points. Both styles are needed as they often take on new land each year with varying conditions.

When it comes time to seed wheat or barley with their air seeder, seed goes into one tank and a trailing liquid cart carries compost extract and worm liquid. They apply the worm liquid sparsely at about 0.5 gallons per hectare to keep costs to a minimum. They also use a boom spray for foliar applications, setting it up with a flood jet system so the extract is applied without restrictions. They were able to apply about 475,000 gallons of compost extract and worm liquid across the crops in 2019, at a rate of 7 gallons per acre at seeding time with the air seeder. In 2020, they applied 660,000 gallons, followed by a 10-gallon-per-acre foliar application post emergence.

The cost to acquire and apply the worm juice and compost extract is about $12 per acre. In ideal rainfall years, Dianne says, the farm is likely to have less crop production than highly fertilized crops, but in drier years — which are 8 out of 10 years — they can often have higher production outcomes and always high-quality grains with high hectoliter weight, good protein and low screenings.

• Retaining Seeds. “Epigenetic progression” is a key part of their farming practice, which includes selfreplacing livestock and retaining seeds every year. Because they are saving varieties, Dianne says they don’t have to chase different varieties that come out “because the seeds we retained ourselves are just improving all the time as they go along.”

Dianne illustrated the difference in pictures that showed the behavior of their wheat seed compared to the neighbor’s, seeded at the same time with the same amount of rainfall.

The photos indicate the Haggertys seed showed a different behavior, as it started developing a root system and engaging soil microbes before it even surfaced to start photosynthesizing. The neighbor’s seed did put on roots but was “really wanting to get out and start photosynthesizing as much as possible,” Dianne says.

“I guess, to me, it just means that our retained seed has got perhaps more energy in it to be able to do more work before it ever needed to start relying upon photosynthesis to recharge its system.”

• Fighting Compaction, Salinity. Compaction might not seem like a big problem in an arid, dry environment, but Dianne says it’s a “massive issue” that they’ve had to contend with on new farms they’ve taken on, along with acid soils. 

Salinity is a problem particularly on land close to Lake Wallambin where salt picked up by wind is deposited on their land. They’ve planted lanes of saltbush and acacia in these areas. They use sheep to graze these areas and contribute to soil fertility through dung deposit. In the more saline areas they sometimes put out hay to attract the sheep and concentrate dung around the feeding point. Many Australian farmers are spending a lot of time and money applying gypsum or lime, or deep ripping on their land as a remedy, but Dianne says roots are able to deal with it without using mechanical systems.

She’s found that the root structure of wheat and oats, for example, are pushing through the acid subsoils and compacted layers. Tests of some new paddocks in the first year and 3-4 years later showed the soil had become five times less acidic without having to incur the considerable expense of applying lime. She notes some farmers 15-20 years ago were applying 1 ton per hectare but are now using 5-8 tons. This also translated into more carbon stored in the soil, Dianne says. As part of a national program to look at soil carbon changes around Australia, researchers tested the soil carbon to a meter and compared similar soil types under different management practices.

The researcher said he hadn’t seen any changes in carbon levels based on differing farm practices, only with different soil types. But after submitting samples, the Haggertys found they were still able to sequester — even with a continuous cereals rotation — a far greater level of carbon than their neighbor with the same soil type.

“What was really interesting was the carbon differences actually increased the deeper we went, so I really reflected what Christine had been saying about having a really good liquid carbon pathway,” Dianne says. “We had about 10 tons to the hectare extra carbon below these biologically managed crops, and there was actually more carbon under the crop than under a permanent pasture paddock, which you wouldn’t really expect.”

Tests also showed their soils were not only sequestering carbon but building nitrogen (N) stocks as well, as the associative N-fixing bacteria were doing their job. “Soil nitrogen levels in our continuous cereal program were higher than the neighbors’, which had included a legume phase in the previous two years. We’ve been able to grow crops with no nitrogen, phosphorus or potassium applied and that’s been happening for quite some time now.”

What is “Natural Intelligence Farming”?

It’s the term Ian and Dianne Haggerty use to describe the harnessing of the dynamic, natural relationships that exist between all the organisms in the ecosystem and the environment itself, particularly the soil. These relationships feature mutually beneficial interactions between the soil, plant seeds and roots, microorganisms, and the ruminants that feed on the plants and cycle manure and microbes back to the soil. Another definition coined for natural intelligence farming, Dianne says, is “integrating nature’s intuitive wisdom and biodiversity with food, fiber and beverage production.”

The key to natural intelligence farming is not to hinder or obstruct the interactions that support and inform these relationships. The Haggertys aim to facilitate natural intelligence with modern farming methods to create regenerative agricultural ecosystems that produce optimal food and fiber products.

MAKING IT WORK. A strategy of notill practices, livestock integration, cover crops and naturally sourced inputs has guided Ian and Dianne Haggerty as they’ve built a diversified 65,000- acre operation in southern Australia. Many parcels they have acquired were previously tilled and are located in different terrains, soils and rainfall zones.

NATURAL FIT. When seeding cereals, the Haggertys inject compost extract and worm liquid in one pass with the seed as a replacement for traditional fertilizers. Then they come back postemergence with a foliar spray of compost extract. Dianne says this setup seems to promote better production in drier years over conventional fertilizer, producing high-quality grains with good protein and low screenings.

COMING BACK. Ian and Dianne Haggerty say their dedication to no-till and “natural intelligence farming” has facilitated some major changes to their paddocks, including the return of native grasses, which provides a more diverse feedstock for their sheep.

DUAL PURPOSE LIVESTOCK. Sheep specifically bred for their wool, and premium-grade fat lambs, are key not only for the farm’s economic diversity, but for integration of microbes and nutrients throughout the Haggertys’ landscape, which spans tens of thousands of acres.

Written by Andrea D. Basche and Marcia S. DeLonge, published: September 19, 2019. Republished under original Copyright

There is a need to develop more resilient, multifunctional agricultural systems, particularly given risks posed by climate change to farm productivity and environmental outcomes [1–3]. Specifically, water-related risks from increased rainfall variability include soil erosion and water pollution, degradation of soil quality, and reductions to crop yields [4–6]. Although soils are vulnerable to water-related risks, they are also being recognized as a medium to mitigate such risk when managed to deliver a wide range of ecosystem benefits, beyond maximizing crop production [7,8]. Thus, designing agricultural systems that improve soils and soil water cycling is one strategy that could help reduce negative impacts of increasing rainfall variability [9–12]. To this point, global modelling analyses indicate that enhancing soil water storage at a large scale can benefit crop productivity and improve ecosystem services, such as by reducing runoff [13,14]. However, there is a need to identify how to secure such outcomes on
the farm-scale, particularly across a range of management practices, environments, and climates.

Emerging interest in how soils can support climate adaptation has increased the urgency to understand the potential benefits of farms shifting from conventional to alternative agricultural practices. Presently, conventional cropping systems typically feature annual crops, leave the soil bare when a cash crop is not growing, have limited crop diversity, and include regular soil disturbance through tillage: within the United States, only approximately 3% of cropland acres are growing a cover crop and 25% are utilizing no-till practices [15–17]. Soil disturbance, a lack of soil cover and limited plant diversity can degrade soils, reducing their ability to withstand rainfall variability through affects such as disrupting aggregation, increasing bulk density, and limiting water holding capacity [18]. In contrast, management practices such as no-till and cover crops may improve soil properties related to water storage such as aggregate stability and bulk density, but they remain in the minority [19]. The limited adoption rates may be in part related to the fact that, in spite of decades of agronomic research surrounding such practices, we are only beginning to understand their potential value for improving key functions related to soil health and water cycling [18].

A growing body of research suggests that a range of alternative farming practices can contribute to biological, physical and chemical transformations in soil that in turn can increase water storage, improving resilience to droughts, floods, and extreme weather conditions [20,21]. For example, studies have shown that no-till, cover crops and crop rotations can in some cases improve soil carbon content, soil biological activity, and soil physical properties associated with water storage [22–27]. For example, no-till avoids disrupting soil aggregates and structure, and cover crops protect soils, particularly during extreme events. There is also evidence that practices such as introducing perennials and designing diversified landscapes, such as through crop rotations or integrating crop and livestock practices, can improve soils in similar ways, likely by providing vegetative protection of soils above- and belowground, and including living roots throughout the year [28–31]. However, because there are a number of different soil water measurements, the effects of specific practices on soil water properties have not previously been well summarized quantitatively [20].

The primary goal of this analysis was to synthesize published field-experiments investigating impacts of agricultural practices on water infiltration rates and to gain insight into mechanisms impacting infiltration rates. We focused on soil infiltration rates because infiltration is a critical ecosystem function that can mitigate drought and flood risk by facilitating water entry into the soil and reducing water losses by runoff [29]. This is a particularly important ecosystem function given predicted climate changes, especially the trend toward increasing rainfall variability, leading to heavier intensity rainfall events and impacts in non-irrigated agricultural regions when there are longer periods without rainfall [4]. Infiltration rates are frequently measured in field experiments and are sensitive to changes in management. Infiltration rates are also closely related to other important characteristics of soils, including physical aspects such as aggregate stability, bulk density, plant available water, as well as chemical and biological aspects including soil carbon, and microbial biomass [20,26,27].

In this study, we considered a range of specific alternative practices that can be adopted on farms, including notill, cover crops, crop rotations, introducing perennials, and livestock grazing on croplands, compared to more conventional controls (experiments with tillage, no cover crops, monocropping, annual crops, and no grazing). We hypothesized that the various alternative practices would increase infiltration rates, but that the relative impacts would vary, and that is the motivation behind including multiple practices in our analysis. We secondarily explored patterns of additional environmental and management factors (e.g. soil texture, climate indices, and the length of the experiment) that we hypothesized could be modulating observed effects.

Methods

Study criteria

We evaluated the effects of various alternative farming practices that can be adopted in otherwise conventional farming systems [32–34]. We considered zero tillage (notill) as compared to conventional tillage, cover cropping or green manure practices that keep soils covered compared to leaving them bare (cover crops), diversified farming (crop rotations, intercropping) as compared to monoculture cropping (crop rotations), agricultural systems with mainly perennial compared to annual crop systems (perennials), and grazing of croplands versus conventionally harvested or hayed fields (crop and livestock) (Figs 1 and 2 and Table 1). The main criteria for inclusion were field experiments that:

1. Measured and reported steady-state infiltration rates, defined as the volume of water entering the soil over a designated period; 

2. Compared one of the alternative practices of interest relative to select conventional controls in a standardized way.

Literature search

The literature search was conducted using EBSCO Discovery ServiceTM (detailed in Basche and DeLonge [25]) and only included field experiments in English language peer-reviewed literature through 2015 (the earliest publication that met our criteria was from 1978). Keyword strings included “infiltration W1 rate” AND “crop*” for all searches, and additional keywords were used for individual practices (Table 1). These searches returned approximately 700 studies, of which 79 fit our criteria. We used the USDA-NRCS Soil Health Literature database [35] to find additional papers, leading to 10 more studies for a total of 89 (Table 1). Information about article rejection can be found in the PRISMA chart in Fig 1. Articles were rejected because they either did not compare controls to treatments appropriately, did not measure infiltration rate, or were otherwise not relevant to our analysis. For additional details, see the Supporting Information.

Management practices

Experiments within each practice were systematically included in the database only if they fit the below additional criteria.

No till: Papers identified from the additional search term “till*” were included if experiments clearly included a notill treatment. We compared any tillage practices–reduced tillage as well as more physically disruptive tillage practices that are typically described as conventional tillage–to zero tillage as the alternative treatment (unlike some metaanalyses that have compared reduced to conventional tillage separately e.g. van Kessel et al. [36]). When papers included multiple different tillage practices that could have been counted as a control treatment, they were further classified as conventional or reduced tillage, based on reported equipment and/or method of plowing.

Cover crops: Papers identified from the additional search string of “cover crop*” OR “green manure” OR “catch crop*” were included when a control treatment with no cover crop was present (e.g. bare soil when the cash crop was not growing). Experiments were included when the cover crop was grown intentionally to protect the soil and was not harvested, and residues were mechanically terminated, chemically terminated, or left as a green manure (e.g. a crop grown specifically for fertility purposes).

Crop rotation: Papers identified from the additional search string of “rotation” AND “continuous” were included when there was a control treatment that represented the continuous (year after year) cropping of one cash crop. The experimental treatment needed to include the same crop as well as at least one additional crop, grown in rotation (as in McDaniel et al. [23]). We included two experiments where an additional crop was grown not in rotation but as an intercrop (i.e. two plant species grown simultaneously on the same field) and one experiment that met the rotation criteria but was different in that it also included grazing in the experiment treatment but not the control (Table A in S1 File). In all experiments, we recorded the number of crops in rotation for analysis.

Perennials: Papers identified from the additional search string of “perennial” OR “agroforest*” included experiments where a perennial treatment was compared to an annual cropping system. This practice represented more significant shifts in management practices that have been the subject of fewer studies, thus we included control practices that varied slightly (for example, they included monocultures with or without conventional tillage). Treatments included perennial grasses, agroforestry and managed forestry (Table A in S1 File). While these treatments have differences in species and management, they share the critical feature of continuous living cover through perennials. Given the limited number of total studies, we aggregated these into a single class (as in Basche and DeLonge 2017 [25]). Two of the eight experiments ultimately included in this practice also had livestock grazing as part of the treatment (compared to an annual crop system with no livestock; Table A in S1 File).

Crop and livestock: Papers identified from the additional search string of “graz*” AND “livestock” were included if there was a crop-only control and a treatment with a similar crop system that also included livestock grazing. This treatment was of interest as it is representative of one phase of integrated crop-livestock systems that has implications for diversifying cropland management. The identified studies included experiments with either annual crop or pasture-based systems, where control systems were harvested conventionally (i.e. with equipment) whereas treatments included livestock grazing and no conventional harvesting. 

Database design

Data from experiments were extracted and categorized systematically. When experiments reported measurements from several years, years were included separately. When experiments included multiple measurements of infiltration rate within a year, measurements were averaged, as has been done in other meta-analysis evaluating soil properties that may be measured on a sub-annual basis [23]. This approach, which was used for 10 studies (and 11% of the response ratios in the database), allowed us to use as much data as possible to capture the influence of the treatments on infiltration rates over a longer timeframe.

We analyzed additional variables to examine how effects of management on infiltration rate are modulated by other factors of interest [23,37,38]. These variables included soil texture (percent sand, silt, clay), climate, study location, and study length. We also analyzed additional information within select practices, including tillage descriptions (within no-till), inclusion of cover crops (within no-till), the number of crops grown in an experiment (within crop rotations), and if crop residues were removed or maintained (within cover crops). Study length was defined as the number of years a treatment was in place, as reported by the authors, and we assumed that this duration explains differences between control and treatment conditions.

We supplemented our dataset using publicly available sources to explore broader patterns that could be influencing the effectiveness of management practices. When annual precipitation was not reported, we used the Global Historical Climatology Network (GHCN)-Daily database [39] (contains records from over 80,000 stations in 180 countries and territories). As an additional indicator of longer-term climate conditions for all study sites, we used locations to extract estimates for the aridity index, an integrated measure of temperature, precipitation and potential evapotranspiration (CGIAR-CSI Global-Aridity and Global-PET Database, resolution of 30 arc seconds [40,41]). In cases where soil textures were not reported in papers from the U.S. (which represented the largest number of studies, Table 1), we used data from the U.S. Department of Agriculture’s Web Soil Survey [42].

Statistical analysis

Statistical analysis was conducted by calculating response ratios, representing a comparison of control treatments to experimental treatments, as is common in meta-analysis methodology43. Response ratios (LRR) represented the natural log of the infiltration rate measured in the experimental treatment divided by the infiltration rate measured in the control treatment (Eq 1) [43]. A weighting factor (Wi) was included in the statistical model as is suggested by Phillibert et al. [44] based on the experimental and control replications (Reps) of each study (Eq 2) [45]. Natural log results were back transformed to a percent change to ease interpretation. Results were considered significant if the 95% confidence intervals did not cross zero.

For statistical analyses, the five practices were analyzed separately because there were notable differences in experimental designs and control treatments. A linear mixed model (lme4 package in R) was used to calculate means and standard errors for the five practices. The statistical model also included a random effect of study to account for the factor of similar environments and locations in the cases where experimental designs allowed for multiple paired observations (e.g. a single study included multiple tillage practices or multiple cover crop treatments using different species) [46]. For the two practices that included the largest number of studies (no-till and cover crops) and could therefore be statistically evaluated in greater detail, additional fixed effects including mean annual precipitation, study length and soil texture, were analyzed with a similar linear mixed model [47].

Given the limited sample sizes for the other three practices (perennials, cropland grazing and crop rotations) additional fixed effects models could not be robustly applied, but figures were developed to explore trends (Figs A-C in S1 File). Regression coefficients were calculated to determine the effect of continuous environmental variables (Table 2). Additional details, including sample R code, are provided in the Supporting Information.

A sensitivity analysis was performed for each of the practices using a Jacknife technique, where individual experiments were removed from the respective databases and overall means were recalculated, to determine how sensitive overall effects were to individual experiments44. This technique provides understanding of how the results would change if individual studies were not included in the database. We evaluated histograms for all practices to determine if there was evidence of publication bias (a preference for published studies with significant effects) [48].

Results
Database description

Through the methodical keyword-based literature search, we identified 89 studies eligible for inclusion in our database, representing 391 paired comparisons on six continents (Fig 3 and Fig D in the S1 File). Many experiments were in North America (31) or Asia (27), with most located in the United States (25) and India (20). More than half of the experiments and subsequent paired comparisons were no-till (207 paired comparisons from 52 studies), while the next largest practice was cover crops (81 paired comparisons from 23 studies). Sixty-three percent of the database (246/391 paired comparisons) demonstrated an increase in infiltration rate with any of the five alternative agricultural practices included in the analysis. Overall means for perennials and cover crops were significantly greater than zero (Fig 4).

No-Till

The overall mean increase in infiltration rates in no-till versus tillage comparisons was not significantly different from zero (5.7%, confidence interval -13.3–24.7%) (Fig 4). Also, we did not find differences between experiments comparing reduced tillage to no-till versus conventional tillage to notill. We found the effects of no-till to be complex, revealing possible conditions and environments where no-till practices are more likely to increase infiltration rates (Fig 5). For example, in the subset of experiments reporting residue management details (11 with residue retained, 7 with residue removed), there were higher increases in infiltration rates in experiments that combined no-till with residue retention practices (41.5%, confidence interval -3.4–86.6%). Only 2 of 52 experiments reported data capturing the effect of no-till plus a cover crop (compared to tillage plus a cover crop) and results were inconclusive (16.2%, confidence interval -94.0–126.5%). Similarly, there was no significant difference when no-till experiments included more crop diversity (in both control and experimental treatments), such as having at least two crops in rotation or double cropping (0.0%, confidence interval -18.9–18.8%).

With respect to environmental variables, we found an effect of precipitation, with significant improvements in regions with 600 to 1000-mm annual precipitation (55.6%, confidence interval 5.8–105.3%) (Fig 5). There were also greater numbers of results where no-till reduced infiltration rates located in more arid environments (i.e., lower aridity indices), but the effect was not statistically significant (Table 2 and Fig E in the S1 File). We did not detect any clear effects of soil texture, nor did we find differences due to study length (Table 2 and Figs F-G in the S1 File).

Cover crops

The mean increase in infiltration rates for cover crop experiments (n = 81, 23 studies) was significantly above zero (34.8%, confidence interval 19.8–50.0%) and results demonstrated a few other important differences relative to patterns observed in no-till experiments. For example, there was a significant improvement in infiltration rates when cover crop experiments were in place for more than four years (30.0%, confidence interval 1.7–51.3%, representing 34 of the 71 comparisons) (Fig 6). Also, we did not detect differences when cover crop experiments were aggregated by annual rainfall or aridity index (Fig 6 and Table 2). There was evidence that the effects of cover crops on infiltration rate improvements were greater in coarsely textured soils with higher sand contents and less clay (Table 2 and Fig F in the S1 File). Similar to the notill plus residue retention experiments, we found there to be a significant increase in infiltration rates when experiments combined cover crops with no-till (compared to no cover crops with no-till; 44.6%, confidence interval 11.6–77.5%) (Fig 6).

Crop rotations

Impacts of crop rotations on infiltration rates were inconsistent, with an overall mean effect that was not significantly different from zero (18.5%, confidence interval -7.4–44.4%, n = 39 from 11 experiments) (Fig 4). Many experiments in our database compared monoculture to two crops in rotation, and only a few compared three or more crops in rotation. Further, in many experiments the control crop was monoculture maize (Fig A in the S1 File). The aridity index analysis revealed that most of the declines in infiltration rate among the crop rotation experiments fell within more arid regions (Table 2 and Fig E in the S1 File).

Perennials

Experiments comparing perennial treatments to annual crops showed the largest improvement in infiltration rates (59.2%, confidence interval 18.2–100.2%, n = 40 from 8 experiments) (Fig 4). These experiments included three types of perennial systems: agroforestry, perennial grasses, and managed forestry (Fig B in the S1 File); they were aggregated into a single group for this analysis because of the limited number of available studies (only eight total met the inclusion criteria) and because they share a key feature of continuous roots in the soil (Table A in the S1 File). Despite differences among and between these practices, the perennial practices showed a consistent pattern in that growing perennial rather than annual plants led to improved infiltration rates.

Crop and livestock (cropland grazing)

Experiments that fit our criteria for crop and livestock systems were more likely to contribute to a decline in infiltration rates overall (-21.3%, confidence interval -50.4–7.9%, n = 24 from 7 experiments) (Fig 4). However, individual studies within this practice suggested that pasture-based and diversified annual crop systems with livestock could lead to improved infiltration rates under some conditions (Fig C in the S1 File). 

Publication bias and sensitivity analysis

We did not find evidence of publication bias in our overall analysis, as shown by histograms demonstrating that experimental results within each practice were not skewed toward very positive or very negative effects (Fig 7). Also, the Jacknife sensitivity analysis revealed robust results, with only minor shifts to overall means and confidence intervals when individual experiments were removed (Fig 8). Results were most robust for notill and cover crops, which had the largest numbers of experiments. However, two practices–crop rotation and perennials–were somewhat sensitive to the removal of individual experiments. When two of the eight perennial experiments were separately removed, the 95% confidence intervals of response rates shifted to slightly cross zero (Fig 8). These experiments were the two with livestock, which suggests that in these environments the presence of livestock did not reduce infiltration [49,50]. For the crop rotation studies, the removal of one experiment [51] led to a significantly different mean from zero.

Discussion

Alternative management impacts infiltration, likely
through biological, chemical and physical processes

Overall we found that the largest infiltration rate changes were associated with practices that entail a continuous presence of roots and soil cover, suggested by the positive improvements of perennial systems compared to annual crops and cover crops compared to no cover crops, as well as the negative trend associated with the crop and livestock systems compared to crop systems only. Determining the exact processes underpinning the observed results is outside the scope of metaanalysis. However, these results point to changes in soil hydrologic function which, in turn, is known to be associated to an intertwined set of biological, chemical and physical factors. For example, physical processes associated with root growth and decomposition contribute to improved soil structure such as porosity and aggregation, which enhances water entry into the soil [52].

Recently, Basche and DeLonge [25] found that cover crops, perennial grasses and agroforestry practices led to significant improvements in two soil hydrological properties related to water infiltration (porosity and water retained at field capacity), which could help explain the effects from those practices in this analysis. The reduced infiltration rates that we found with respect to the crop and livestock studies could be related to the removal of vegetative cover or soil compaction from grazing, although the available studies for this practice were limited [53–55]. Overall, our results suggest that management has an important contribution to infiltration rates, and that these are likely related to soil physical changes.

Given established relationships between soil carbon and soil water properties [26,27], one factor that likely has a role in our findings is the impact of carbon accrual from the analyzed practices. For example, increases in soil carbon have been quantified by meta-analyses in response to cover crops, crop rotations, and other conservation practices [7,23,24]. Also, perennial systems typically store more soil carbon than annual croplands [56–58]. However, reviews evaluating the effect of no-till on carbon have found mixed results [22,59–62], similar to the complex no-till findings in the present analysis. Specifically, these reviews have found that no-till can lead to carbon accrual in some instances but may also lead to no net increase in carbon but rather a redistribution of carbon closer to the soil surface [59]. Further, it has recently been demonstrated that the relationship of soil carbon to soil available water may not be as strong as indicated by prior analyses [63].

Continuous cover of the soil combined with reduced soil disturbance is known to promote enhanced biological activity, with is also linked to physical soil structure. For example, management practices leading to a greater number of earthworms could contribute to soil aggregation and pore creation, increasing water entry [64,65]. A recent meta-analysis found that reduced tillage increased earthworm abundance and biomass by more than 100% compared to conventional inversion tillage [66], suggesting a potential biological mechanism that may help explain the success of no-till in improving infiltration rates under some circumstances.

Cover crops have also been found to increase earthworm populations and recent work finds that they also significantly increased microbial biomass as well as mycorrhizae colonization across a range of experiments [67–69]. Increased biological indicators such as earthworms, microbial communities, microbial biomass and/or mycorrhiza colonization might also be expected in other practices that promote crop diversity and year-round growth, such as crop rotations and perennial systems, potentially facilitating higher infiltration rates through their effects on soil structure as well.

While increasing infiltration rates may mostly be considered important for reducing flooding risk, the previously discussed soil improvements can play a role in reducing the impacts of drought. A recent global meta-analysis found significant improvements from conservation tillage on soil hydrological properties such as aggregate stability, aggregate size, saturated hydraulic conductivity and available water capacity [70]. In particular, increasing available water holding capacity and soil organic matter are understood to increase the likelihood that water will be stored and/ or utilized when drier conditions or drought arise [18].

Further, there is growing evidence that increases in soil organic matter and available water holding capacity are associated with increased yield stability, in particular through increased use of conservation agriculture systems [71,72]. Although tradeoffs may arise between alternative management and crop yields, the results of this work and prior work suggest that they can also improve the soil while increasing yield stability, important benefits to consider in the context of rainfall variability and climate change.

Comparing the efficacy of different management
practices

Our results suggest similarities and distinctions between alternative management that are in many ways corroborated with past studies that have limited their scope to a narrower range of practices. For example, the overall finding that continuous soil cover can improve infiltration rate is corroborated by prior research focused on cover crops or agroforestry. A recent meta-analysis of eight experiments in Argentina found a similar effect of cover crops on infiltration rate, where infiltration was increased by an average of 36% due to the presence of cover crops compared to no cover controls [73]. Also, Ilstedt et al. [74] found that afforestation and agroforestry increased infiltration rates relative to annual crop systems by 100–400% across four experiments in tropical agroecosystems.

Somewhat contrary to conventional thinking around no-till, our global meta-analysis found that no-till did not consistently improve infiltration rates at this scale. In contrast to our findings, a recent qualitative review (mostly from studies within the United States, in both wetter and drier environments) found that notill in most instances increased infiltration rates over conventional tillage [37]. Also, a review of experiments in the Argentine Pampas, a humid environment with well-drained soils, found that no-till doubled infiltration rates [38]. While our results did demonstrate a trend toward improvement, our database included very few cases where infiltration rates increased by at least a factor of two as a result of no-till, even in humid environments (16/207 paired comparisons; Table A in the S1 File).

Also, we did not find a significant effect of no-till in the subset of no-till experiments including cover crops (Fig 5), contrary to our findings in for cover crops (where cover crops increased infiltration rates within the subset of cover crop studies with no-till, Fig 6). This inconsistency may be related to the limited number of no-till experiments reporting infiltration rates for combinations of factors, such as use of cover crops, which would have allowed more comprehensive analysis. We did, however, find that notill experiments with residue retention were more likely to increase infiltration rates, suggesting the importance of combinations of practices to maximize benefits.

Crop rotations had an inconsistent effect on infiltration rates. We did observe a negative effect of crop rotations on infiltration rates in drier regions (Table 2; Fig E in the S1 File). However, the studies that met our criteria were largely from more arid regions, so the limited dataset may have inhibited analysis across a sufficiently wide range of aridity regimes in order to detect stronger overall effects. In a meta-analysis that similarly considered conventional management versus crop rotations but focused on soil carbon, McDaniel et al. [23] found that crop rotations generally increased carbon, but that greater increases were correlated with more precipitation.

Thus, the study revealed a sensitivity of crop rotation impacts to climate, potentially related to small decreases in bulk density that may have affected soil hydrologic function [23]. Together, these findings suggest a need to closely monitor the impacts of crop rotations on several soil variables, especially in drier environments. This may be especially important for this practice, as there is already great deal of variability in the crop diversity and level of complexity of crop rotation practices.

Although limited experiments fit our criteria for crop and livestock systems, the overall result suggests that careful management of these complex systems may be necessary to maintain or increase infiltration rates. While the mean change in infiltration rates was negative across all studies, individual experiments suggested that a positive effect was possible under some circumstances and management practices. For example, Masri and Ryan [75] found infiltration rates increased when a diverse annual crop rotation included livestock as compared to when the systems included crops only. Franzluebbers et al. [76] reported increased infiltration rates in pasture-based systems with versus without livestock, but only when a lower grazing intensity was utilized. It is also important to note that cropland grazing typically represents only one component of a diversified farming system that may have different outcomes when assessed on a larger scale [77].

Uncertainty surrounding measurement timing and
experiment duration

One variable potentially affecting our results could be related to a sensitivity to the timing of measurements in these experiments. This sensitivity may be particularly relevant for the no-till studies. For example, immediately after a tillage event, the infiltration rate in tilled fields could increase relative to no-till because of managed decreases in bulk density [37]. An experiment included in this analysis [78] found greater seasonal differences versus treatment differences when comparing tillage practices to no-till. Our database could not be categorized according to inter-season periods of measurement and management, as such analysis would have been complicated by inconsistent data availability and was beyond the scope of our study. As such, we were only able to evaluate overall trends based on available data and these limitations likely account for some uncertainty in our analysis.

Another related variable that could be introducing uncertainty is the lack of studies reporting effects following a wide range of treatment durations. In our analysis, we did not find experimental length to be a significant factor in our analysis across any of the practices (Table 2; Fig G in the S1 File). This finding therefore does not support the common convention that management practices need be in place for an extended period of time in order to demonstrate improvements to various soil properties. Instead, we found that even after a short period (as little as within the first few years) it was possible for infiltration rates to increase relative to conventional controls in some cases (for example, for some crop rotation and perennial experiments, Fig G in the S1 File). At the same time, longer experiments did not consistently lead to more significant changes. This finding could also be related to the interannual timing of measurements, as infiltration rate is a dynamic process subject to interseason and/or interannual variability. However, examining such effects was beyond the scope of this analysis, as the primary goal was to detect infiltration rate changes between different farming practices.

Uncertainty surrounding data limitations and research
gaps

Overall, our results revealed the varying relative abundance of experiments evaluating different practices; no-till experiments comprised more than half of our database, while many fewer experiments evaluated practices such as perennials or crop and livestock systems. This observation aligns with recent findings indicating that more complex agroecological research receives relatively limited research funding [79,80]. While we did find several studies for each practice, our sensitivity analysis revealed that the limited number of experiments in some led to more sensitive results. Smaller sample sizes also limited our ability to explore influences of other environmental and management factors (e.g. we were able to comprehensively evaluate the effects of precipitation and soil texture only for notill and cover crop practices).

Additional levels of analysis that also consider the combined and synergistic effects of multiple management practices would also be valuable. For example, it would be interesting to compare the combined effects of no-till, cover crops, and crop rotations (typically combined in conservation agriculture systems) as compared to conventional agricultural systems. However, such analysis was beyond the scope of this study and would be challenging given the very limited number of experiments that combine practices and report results in a sufficiently similar way to directly compare controls and treatments. More complex, wellreplicated, and long-term studies would be needed to enable a similar meta-analysis to the present study, but with this broader scope.

In general, a lack of detail on environmental and management factors was another important gap in our analysis. Gerstner et al. [81] and Eagle et al. [82] proposed criteria that field experiments should include to increase their utility for meta-analyses or synthesis reports, in the fields of agronomy and ecology. These criteria include environmental features, such as soil and climate characteristics, as well as reporting complete factorial results from experiments.

Conclusions

The overall trend quantified by this analysis is the potential for improvements to infiltration rates with various alternative agricultural management practices, with the greatest benefits observed in response to introducing perennials or cover crops. Our findings suggest the importance of the presence of continuous living plant roots and the positive soil transformations that accrue as a result. We found that no-till practices did not consistently increase infiltration rates but were more likely to do so in more humid environments or when combined with residue retention. Another important finding is that some practices have been substantially less studied than others, particularly ones that show some of the greatest promise for facilitating water infiltration such as the use of perennials. 

Future work should explore greater opportunities for expanding practices such as perennial integration into agroecosystems to facilitate improvements to water infiltration. Further, more complex, long-term field experiments that evaluate alternative systems rather than individual practices would benefit our understanding of agroecosystem designs for optimal water outcomes. Additional research is also needed to better understand the potential synergies between optimal water outcomes and other ecological benefits at several scales, such as in relation to soil biology, nutrient cycling, and drought and flood impacts. Utilizing alternative practices that increase water infiltration rates offers the opportunity to mitigate effects of extreme weather that are expected to grow more frequent with climate change.

The Gentle Farming system will produce the first carbon offset certificates in the Autumn. The buyers can see a portfolio of local farms or those that reflect their needs. Gentle farming will sell the offsets and begin paying farmers this winter.

Written by Thomas Gent from Gentle Farming

We have had a busy few months moving things forward both in terms of working with farmers and agronomists and also in creating interest from potential companies wanting to invest in their local regenerative farms. We now have over 30 farms subscribed and using the system this harvest to verify their regenerative farming practices and calculate their carbon offset potential. In turn this leads to us being able to produce certified soil carbon offset certificates and to being able to verify these farms are improving their soils and producing food in a carbon friendly way. Free training has been offered to agronomists to build and share knowledge within their industry and so that they can assist their farmers to understand the opportunities within regenerative farming to generate new income streams. Consumers are becoming much more aware of the eco credentials of companies they choose to buy from as well as wanting to connect much more deeply with nature following the COVID pandemic.

This shift in consumer interest is only on the increase with recent reports showing consumers are willing to pay more and actively seek out eco-friendly products. This means there is an increased focus and urgency by businesses into how to deliver this for their customers and meet their own challenging carbon targets. As I speak to corporate sustainability departments and consultants I see that there is a strong demand for local UK based, high quality environmental projects and sources of offsetting that these businesses can invest in.

Gentle farming and its certification partner CommodiCarbon has a methodology that will validate soil carbon offsets taking place on farmland soils and verify the regenerative practices that underpin this soil improvement. The NFU have published their pledges and set their Net zero target goal for 2040. (Only 19 harvests away!) With supermarkets and other industries setting even more ambitious targets we simply do not have the time, action must be taken now. Farming and forestry are among the few industries with potential to sequester more carbon than they are emitting from their activities.

This will require great change which must be supported financially as strong financially viable farms will be in a position to invest in their soils and push the boundaries of new techniques and technology. Carbon offset income streams will contribute to this as will the possibility of increased demand for carbon friendly produce. But carbon is just the start of this new market development. Water and building companies look to improve the local biodiversity of their projects. Regenerative farming can offer a huge range of environmental projects for businesses to support and invest in. The key is to have a structured high quality certification and validation process. Which will be the basis for selling soil carbon offsets but also lead to other opportunities in water improvement, biodiversity improvement and higher quality produce coming from these farms.

The Gentle Farming system will produce the first carbon offset certificates in the Autumn. The focus will be to build a website that gives a shop window to each individual farm by creating a profile that highlights the story of their farm and the environmentally beneficial work they do. The buyers can see a portfolio of local farms or those that reflect their needs. Gentle farming will sell the offsets and begin paying farmers this winter. I hope that having a group of high-quality soil focused farmers and a system to verify their carbon offset will lead to other opportunities within their community and supply chains, for example selling grain at a premium price, investment in environmental projects, marketing for other diversification projects.

Marketing this in the right way with the right story and a young ambitious brand to sit alongside it I believe has the greatest potential to make a difference in terms of rewarding and recognising the hard work that goes into being a nature focused farmer. I think that regenerative/ sustainable farming practices are going to boom in the next decade and the farmers already on this journey can and should lead the way. Most people talk about all the problems coming in the future, I can’t help but smile and all I see is opportunities to make a difference and encourage more people to love the soil that feeds us.

Mark is a farmer and agronomist from Withybrook in Warwickshire. After starting with ADAS in 1996 and working with NIABTAG, AICC and Agrii he was awarded a Nuffield Scholarship to evaluate the role agronomists play in stewarding pesticide use.

Think of Denmark and you might imagine bacon, pastries, Hamlet and Carlsberg. You might also think of a country which relies almost exclusively on ground sources for its drinking water supply; probably the best drinking water in the world. To maintain this particular public good, Danish farmers have been subject to environmental protection laws and restrictive practices on pesticide use for 35 years. One of the most valuable visits on my Nuffield Scholarship tour was with Søren Thorndal Jørgensen who leads the coalition of farming and agronomy interests and negotiates with the strong environmental protection lobbies in Danish politics. His experience is one which I believe will be crucial to gain in the next decade here in the UK. Pesticide use is under a political spotlight in the context of a new National Food Strategy, revision of the National Action Plan for sustainable pesticide use and from across the English Channel and North Sea with the EU’s Farm to Fork strategy and its 50% pesticide reduction target by 2030. UK legislative response is currently in gestation.

I sense a change in the attitude of farmers as well as legislators and the pesticide supply chain which is palpably different to that which I saw three or four years ago. That’s when I first made an organised attempt to evaluate our relationship with pesticides and the role that agronomists of all kinds play in that evolving affair. Successive product revocations and the build-up of resistant weeds, pests and diseases have had their effects on use. Temporarily use has increased (think of the pre-em and triazole “stacking” we talked about more enthusiastically a few years ago) but this last hurrah may be giving way to a progressive movement towards regenerative practices which rely less on pesticides and more on the adoption of resilient systems. Groundswell captures the zeitgeist. Although the mood seems to have changed, the data to support this apparent shift in attitudes is not as easy to detect; the Pesticide Use Survey reports increases in pesticide used on arable crops measured by both weight and treated hectares.

The effects of pesticides on biodiversity are Implicit in their role and we all want, or at least are under pressure, to use less. But how?

Integrated Pest Management has long been heralded as the solution to pesticide reduction, but as the graph shows, in the decade prior to 2018 we used increasing amounts while simultaneously adopting IPM plans as a compulsory part of the Red Tractor assurance schemes. Other studies have also recorded concurrent increases in pesticide use and adoption of IPM practices. It’s perfectly possible to use more pesticides while simultaneously using more cultural controls. It’s clear we need to do more than fill out an IPMP to demonstrate our sustainable approach to pesticide use. Back to Denmark and of all the policies, good and bad, put in place since the 1980’s the word from the coal face is that the recipe for success is simple: engage with the debate, make reasonable changes, evolve the approach and communicate the success.

At the heart of the Danish experience has been the evolution of the metrics used to assess trends in use. Weight of product and treated area have limitations on their usefulness as they take no account of the equivalent effects of the products being used. A step in that direction was one which Denmark took in recording Treatment.

Frequency Index (TFI) which measures the number of full rate equivalent applications made to a crop. TFI is a progression from weight and treated area as a proxy for pesticide related harm. It takes some account of the relative equivalence of different pesticide products because it relates to the full recommended rate for a particular product which was authorised partly by reference to its potential unintended effects. TFI also has the benefit of being very easy to calculate. Software providers would have very little work to do to allow this measure to be generated as a report for scales right through from field,

farm and agronomist, through to region and nation. It would provide a comparative, up to date picture of our pesticide use at the touch of a gatekeeper icon. The initial targets put in place for reductions in TFI were predictably missed in Denmark. Those which were implemented in France more recently have also been missed. The thing these two examples have in common is the lack of stake-holder engagement when setting targets. When more stakeholder engagement in Denmark was sought and the targets were evolved then the success started to flow.

Learning points from these experiences for effective pesticide reduction strategies incude:

• Select appropriate metrics

• Engage the stakeholders when targets are determined

• Review progress and evolve the approach

Since completing my Nuffield Scholarship, I have taken the study further with regard to pesticide metrics and their role in reduction strategies, applying the academic rigour of an MSc course at Abersystwyth University to what I learnt on my travels. I incorporate my combined conclusions in the way I believe we should apply them to the UK context and believe we should:

• Introduce Treatment Frequency Index as a reporting requirement for Red Tractor assurance schemes on the basis of 3 year rolling averages to reduce seasonal bias.

• Agree reduction targets with stakeholders through a body tasked with the Responsible Use of Pesticides in Agriculture (RUPA)

• Keep the system under review. This process represents a journey, not a destination.

This process must be led by a coalition of interests. By using use the word led I imply the need for leadership. Leaders in this area have been scarce to date and that void needs to be filled before the opportunity to lead change is supplanted by the obligation to carry out change according to poorly conceived legislation.

The drop in Antibiotic use in UK Pigs

In all my Nuffield travels I didn’t find a better example of this approach than the organisation Responsible Use of Medicines in Agriculture (RUMA) in the UK which has widespread industry support. It was founded in 1997 and was tasked with overseeing the responsible use of medicines in livestock production. In May 2016 Jim O’Neil published a report titled “Tackling Drug-Resistant Infections Globally” which applied the sort of political pressure on antibimicrobial use which we are seeing with pesticides today. RUMA created their Target Task Force, the mission for which is to move closer to optimal use of antibiotics.

RUMA members’ acceptance that historic use was, in some areas, super-optimal has resulted in reduction targets that have both improved their production systems and is satisfying the objective of reducing antimicrobial use. Results have been impressive (as in the graph from RUMA’s 2020 report) and are credited with the avoidance of draconian legislation. It may be a coincidence, but the active ingredient loss experienced in plant protection products does not seem to have affected animal health products in the same way. The leadership and success evident in animal health product stewardship is something the UK pesticide industry should be trying to emulate.

There are some further parallels between this process and the way net carbon emissions are calculated which has evolved more rapidly in recent years. Exemplary leadership has pushed the goal of carbon Net Zero to the top of the agenda.

Although all these reduction strategies need to adopt common measurements and agree targets, there is a different finishing line between pesticides and carbon. Agricultural activity has the capacity to sequester carbon at different rates and can offset the unavoidable element of associated carbon emissions, so while we may achieve net zero, we cannot achieve absolute zero emissions. Unfortunately, the same offsetting opportunities do not exit with pesticides Perhaps the target we should aim for with pesticide use should be a net zero impact on biodiversity. Zero use may be a target for some stakeholders, but I cannot quite yet envisage a world where we are in an overall better position with zero use of pesticides, given their potential to augment food security through their judicious use. Then again, in 1996 I said I couldn’t envisage the time when I would want to use the internet.