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By Nathan Morris, Elizabeth Stockdale, David Clarke – NIAB
Long term findings from field-scale experiments (STAR and NFS) show that while yields with non-inversion tillage are similar in most years to yields with ploughing, when decreased costs of labour and fuel are factored in, gross margins under non-inversion tillage were better than under ploughed systems. Hence non-inversion tillage is advocated under ‘normal’ conditions.

The influence of primary cultivation method on crop yields will no doubt continue to cause debate, but long-term findings from the STAR (Sustainability Trial for Arable Rotations) and NFS (New Farming Systems) projects are giving some hard evidence of impacts across seasons and soil types. The long running STAR project in Suffolk (medium/heavy, clay loam soil) and NFS studies at Morley in Norfolk (medium/light, sandy loam soil) started in 2005 and 2007 respectively. Both studies therefore allow us to study impacts over the long-term and have allowed the impacts of the tillage systems to become established. NIAB co-ordinates and manages these trials but they are funded by a number of charities. The Morley Agricultural Foundation (TMAF) and the JC Mann Trust provide continued support for the NIAB New Farming Systems projects; the Felix Cobbold Trust and, historically, the Chadacre Agricultural Trust provide support for the STAR project.

The STAR and NFS projects are field-scale trials using farm scale equipment and techniques with fully replicated large plots. The experiments have the same primary cultivation treatments; however, the difference in soil type between the two sites provides an important contrast when considering tillage impacts. The proportion of particles of different sizes (soil texture) that make up the soil have a large impact on the soil structure and properties such as trafficability and workability. For example, clay soils usually have more small pores than sandy soils and these can hold on to more water for longer. Soil structure results from the interaction of the mineral particles (sand, silt and clay) with soil organic matter as they aggregate together to form the crumbs, blocks and other aggregates that we see when working the soil. In some ways, it is the gaps (pore space) between these aggregates that is the most important part of structure as the pores control the balance of oxygen and water available to plant roots and soil organisms. 

Cultivation has a key role in shaping the soil structure. However, plant roots and some soil organisms (known as ‘ecosystem engineers’) also change the structure of soil by moving through the soil, moving soil particles around and extracting water. Along with a range of physical (drying-wetting) processes, these biological interactions have a central role in soil structure development and create micro-habitats for other soil organisms; in temperate agroecosystems, earthworms are very dominant within this group. In the STAR and NFS trials we are comparing 3 contrasting primary cultivation practices: inversion (c. 25 cm plough) and non-inversion tillage (using the subsoiler / disc-based combination, e.g. Sumo Trio) set either deep (c. 20-25 cm) or shallow (c. 10 cm).

These systems are used typically for primary cultivation each year to give the three main treatments. In addition, each study also has a treatment which allows a ‘managed approach’ where the cultivation system used changes with study, season and crop. The annual cultivation decision in these treatments is based on soil conditions, field assessments, previous cropping, weed burden and local best practice (see Table 1 and 2). Secondary cultivations (e.g. power-harrow, press) are used as needed on a treatment by treatment basis. The specific crop rotations used also differ between the sites, however, in both studies rotations employ only combinable crops and include regular winter wheat alternating with combinable break crops.

Winter wheat yield

In both STAR and NFS the regular cropping of winter wheat in the rotations provides a unique opportunity to examine the impact of primary tillage on long term performance of first wheat yields in large scale fully replicated studies. Statistical analysis has focussed on the ‘consistent systems’ (where treatments have remained the same over this time period). Winter wheat yield data for from harvest years 2, 4, 6, 8, 10 and 12 of STAR project are presented in Table 1. Analogous data from harvest years 1, 3, 5, 8 and 10 of the NFS Cultivations study are presented in Table 2. In both studies, winter wheat yields vary markedly with the season; i.e. year has a statistically significant impact on yield. In terms of the impacts of tillage systems, there is no clear pattern in all years.

Considered on average across seasons, in STAR there is no difference in the yield of the different primary tillage systems. In NFS taken across all years, there is a significant reduction in yield (-4%) in the shallow non-inversion systems compared to the other approaches; however, the difference is not significant in any individual year. This is possibly associated with the lighter soils being more prone to loss of structure where some rectification / management is not used. Overall these findings suggest only small percentage yield reductions with shallow tillage (cf. plough systems) indicating that wheat yields are relatively robust with respect to the tillage approaches assessed on these sites. More data analysis and crop modelling may help to explain the differences in the treatments year by year e.g. in terms of the direct impact on seedbed quality and consequent establishment.

At STAR the managed approach to cultivation gives a slightly higher average yield compared with the treatments where the primary cultivation techniques are applied consistently. At NFS yields are 4% lower under the managed approach compared to deep and plough tillage, possibly as a result of the high proportion of shallow tillage used (3 out of 5 years).

Winter wheat margins

When considering gross margins, both STAR and NFS non-inversion treatments (shallow and deep) resulted in greater margins in first wheat crops compared to the plough. For deep non-inversion treatments this benefit was 6–7% and for shallow non-inversion treatments gain was 1–4%. Margins were also increased in the managed approach compared with the ploughed treatments. However, in addition to margin it should also be noted that ploughing would have also resulted in slower speeds of working (cf. non-inversion tillage systems); this would potentially improve a farmer’s capacity and hence ensure timeliness of operations over the total farm area. This is potentially of greater importance than small differences in rotational margin. 

Other impacts

In soils under non-inversion tillage, we found increasing tightness in soils in the upper subsoil; however we also sometimes found large improvements in soil physical conditions over a growing season driven by the growing crop. Where there were no changes in the organic matter inputs, there were no gains in carbon storage over the whole soil profile under noninversion tillage (compared with ploughed systems). However, with non-inversion tillage, organic matter becomes more stratified in the soil with higher amounts in the surface soil and lower amounts at 20-25 cm compared to ploughed plots. Currently herbicides are managing the weed burden on all treatments effectively – however, this year we are monitoring some un-treated areas to assess the role of the primary cultivation strategies on the weed seedbank.

Overall, the work in these studies and others is confirming that alongside decisions about primary cultivations, farming systems that support the biological processes of structure formation and increasing soil organic matter content have been shown to help create resilient soil structures that can both absorb heavy rainfall and hold water in drought; however, there is still a way to go before we have fully uncovered the mechanisms supporting structural resilience. 

Acknowledgments and thanks are extended to The Morley Agricultural Foundation (TMAF) and The JC Mann Trust for their continued support of the NIAB New Farming Systems programme; also to The Felix Cobbold Trust and historically The Chadacre Agricultural Trust for their support of the STAR project.

Written by Maxime Barbier. First Published in TCS Magazine N°97 in March 2018

With the list of agrochemicals that is available to agriculture constantly shrinking and a threat hanging over the use of glyphosate, there is a growing interest more and more in alternative weeding solutions. All over the world many alternatives are being investigated; electricity, microwaves, thermal foam, water jet and bio herbicides. However a cheap and reliable alternative systemic weed killer at the same unbeatable price as glyphosate is not available currently. But who knows, from the emergence of all these innovations there will perhaps come new tools to help control the most challenging weeds growers and farmers face.

Will these alternatives consolidate or even improve our systems in both Conventional and Conservation Agriculture systems? The first problems appeared with the beginning of agriculture. Without the domestication of animals and crop raising we would probably have had to stay as hunter- gatherers, feeding on berries, acorns and wild meat. So busy finding food we wouldn’t be able to write this article! We evolved from largely a dense forest canopy of oak and beech to a succession of annual plants which has led to an incessant energy expenditure against Mother Nature who only wishes one thing; to return to a balance of perennials.

A struggle, helped in recent decades through the development of synthetic herbicides, has allowed us to maintain a perpetual crop of annuals. Now the list of usable agrochemical products as well as their efficiencies is decreasing, the situation is more and more urgent to find replacement techniques. Encouragingly, solutions exist already and interest is much revived and accelerated with the regulatory and consumer pressure on the use of glyphosate.

A complete herbicide through using an electrical current

The use of electricity as weed control technology was invented in the early 20th century but little interest was shown in the technique and had been largely forgotten due to the growth of synthetic herbicides after the Second World War. The first patents were issued in 1913, however it wasn’t until 1990 that the researcher NippoBresilien Satoru Narita, restarted the research on this method of weeding, with the help of private funds from a large owner of a forest that wanted to manage his weed problems which including herbicide resistance in some areas of the plantations he owned.

A project 10-year research was set up with the University of Brazil and in partnership with a Brazilian private sector company Sayyou, the first prototypes were launched in 2012. Large-scale trials of electrical current have been conducted in forestry and horticulture and also on wheat, soya, and citrus plantations. One major benefit is that the systemic action killing the whole plant. The current destroys both parts of the plant. The foliage and its root, preventing the plant from being able to regenerate.

“In the tests, the level of weed regrowth after 3 or 6 months is comparable to treated plots using glyphosate” says Benjamin Ergas, director of the company Zasso Group AG, from which Sayyou (now Zasso Brazil) is now part. Indeed, the machine, called the Electroherb, is distinguished by a destructive effect that kills foliage of the target plant to the root system. This mode of action is possible because the machine runs on a closed circuit. The PTO generator transfers the electricity to a row of “plant” applicators located on the front linkage made up of metal spatulas spaced every (10- 20 cm). Working widths are available from 1 to 10 meters. These applicators are interchangeable with a cultivator. As the spatulas touch the plants, the current flows through the tissues returning through a second row of spatulas which act as an earth closing the circuit. By getting into the vegetative parts of the plant, electricity has the action of breaking the vessels and damaging cells.

The machine delivers a high alternating current frequency (3-30 kHz), with a voltage (5,000-15,000 V), the charges usually don’t exceed 6000V. The dose of voltage is determined by field conditions and type of plants encountered. “The system self regulates according to many parameters: height and density of foliage and weed roots, soil moisture and density, topography, tractor speed and lastly width of Applicators. There are several patents that revolve around this problem, the main challenge being to provide a continuous and stable feed of current” explains the director. The energy needed varies from 100 to a 1,000 joules, enough to dry out foliage without burning or cooking it.

The destructive effect is better in full sun, although the manufacturer indicates that the machine can operate under most conditions, except heavy rain. There are less favorable conditions at dawn, because of the dew, and also when the plants to be destroyed are very close to the ground. In this case, the current may tend to dissipate more easily, the loss of effectiveness can then be order of 10% “ comments the specialist. The machine seems to have a useful action on dicotyledons, identified as having non-parallel leaf veins, tap roots and seedlings with two cotyledons. “The lower the dry matter of the plants, the more they are sensitive to the electrical current. This is equally the case for their root structure also.

Weeds with rhizomes like wild buckwheat are harder to destroy than grasses, which have a network of roots more which are more concentrated.” explains Matthias Eberius, technician at Zasso. New evaluations in 2018 were carried out in France. “We tried the prototype on organic plots of soybeans sown direct in the stubble of the previous crop. The technology is very interesting in organic systems as it may be possible to evolve towards a direct seeding approach. The operation was used just after sowing because we have a window of 5 days before crop emergence. The tool has controlled annual weeds, which measured between 5 and 25 cm above ground.

Control was less effective on some perennial plants, especially those well-established root systems, where it took two or three passages to achieve a kill. In our conditions, we must also be careful that the soil is not too wet so as to cause compaction because of the weight of the machine. In terms of diesel consumption, we’ve seen numbers between 10lt and 12 ltr / ha “, says Marcio Chaliol, from the Swiss company Gebana who supervises a group of organic producers “ABC” in southern Brazil. Since, the manufacturer worked on the machine weight, they have sold 15 machines in Brazil weighing on average 800 kg (200 kg for applicators and 600 kg for the generator). The aim is nevertheless for a significant weight reduction for future agricultural equipment.

The current working speed of Electroherb is around 3 to 5 km / h, although it is possible to go up to 10 km / h. The biggest constraint remains the contact time between the electrodes and the plant: it must be between 0.1 and 1 second dependant on the height of weeds present. With a current width of 2.5 m to 3 m wide, the machine has a work rate of 1 ha/hour. In terms of risks to soil fauna, worm tests of earth and springtails are in final stage of testing. At the moment, the final report is not available but according to the manufacturer, the impact is limited. “The results of tests carried out in 2017 under normal conditions and typical dose rates, did not show any significantly negative effects on earth worms, soil mites and microorganisms.

However tests carried out in non-targeted areas under normal use of equipment, such as wet permanent pasture, have revealed a sensitivity at very high doses, says the director. The scheduled tests for 2018 will seek to evaluate the dosage optimal for ensuring complete destruction of weeds while having minimal impact on non-target organisms. Is the magnetic field potentially harmful for the user? “Intensity of these fields was measured and the main source of radiation comes from the generator, which is shielded. The applicator’s radiation field that is produced is well below critical values for man and the environment” concluded Mr. Eberius. The price of the machine has yet to be announced by the manufacturer. They hope to launch the machine on the market in 2019.

By then, Arvalis and the French Institute of vine and wine will have finished conducting assessments on the safety of the machine. The current version will be available for demonstration in France in second half of the year.

Microwaves for “Cooking” weeds.

Another technology that has the advantage of not touching the soil is weeding by microwaves. Created initially in order to warm up frozen dishes, his interest in destroying unwanted plants has been studied since 1920. From pizzas to weeds, there is only one step. Graham Brodie, of the University of Melbourne in Australia, in 2006 used a kitchen microwave with a power of 600 watts to study its weeding potential. “Microwaves make the water molecules contained within the food stuff or plant to oscillate very fast.

Plant moisture is transformed into steam that generates a strong pressure that will degrade the cellular structure. It’s also very impressive to hear the vegetation cracking as the machine moves across the field”, says Graham Brodie. Since 2008, he has been developing an experimental version with a power of 8 kW. It consists of four independent generators of 2 kW each. The output antennas are 11 cm wide which allows the wave to be directed between rows where cultivation has taken place. “The tool is used at a speed of 1 km / h, which generates a temperature 60 ° C on the floor, enough to eliminate weeds at a young stage. With a power of18 kW, it would be possible to work between 6 and 10 km / h, and there are already generators of nearly 100 kW “, he says. The machine is also used to treat the soil in order to reduce the weed seed bank and will also destroy some organisms, pathogens such as nematodes, bacteria and fungi various fusarium and slerotium).

This operation however requires much more energy and operates at a much slower forward speed: 40-50 m / hour. The effect on weed development, on the other hand lasts for much longer. Of the tests carried out before sowing cereals (rice, wheat) it was showed that under certain conditions a weed pressure reduction up to 85% over to the untreated cultivated land. The tests have also shown gains in yields that varied between + 35% and + 92%. “Microwaves will only penetrate to 5 cm, but that is enough to kill some of the bacteria present.

Which is the same as a tillage operation but without the soil movement. This destruction also causes a mineralization effect and the release of nitrogen is where the yield increase comes from. Populations of bacteria regenerate very quickly and after a few weeks, there are more bacteria than before the passage of the machine. It was noted that this effect on the soil treatments performance persists even during the next three seasons, “added Graham Brodie.

Microwaves also have a positive effect on slugs.

 In addition to weeds, the technology helps to control slugs and snails. Tests show, the energy required to kill them was ten times less than those needed to destroy the plants present (see table). The flip side or these kill rates also relates to their effect on earth worms and all other useful macro fauna that can be found on the soil surface. “At this point we don’t know the effect of this on this macro fauna. Microwaves will probably kill earth worms very close to the surface just as a tillage pass would.

Those at depth are protected because the effect is not going below 5 cm”. The other major drawback of this technology is energy consumption. The 8kW machine needs two electricity generators of 7 kW. There is therefore a loss of energy inherent in the process of running the machine that emerges as heat lost to the atmosphere and which is not recovered. “The efficiency of a household microwave is less than 50% whereas in the agricultural system current is around 75-80%. But industrial generators in closed systems ensure efficiencies of 90%, concludes Graham Brodie.

Further green chemistry

In addition to these mechanical technologies, another solution to consider is bio herbicides. These are obtained from natural active molecules found in living organisms: bacteria, fungi, and plants. A quick overview of available solutions brings one particular product to the top of the search. Marketed by the company Jade, this is a product which has gained approval for field crops in France. Belukha is non-selective herbicide consisting of pelargonic acids (nonanoic acid), an acid fat obtained after during the extraction process for rapeseed oil.

These molecules act by contact dehydrating the cells of the plant, causing it to dry out. Belukha is a non-systemic product. In 2018 it was approved for use on vines, fruit trees and for desiccation of soil beneath the apple trees. Like all products of this type, it is advisable to apply in the spring or summer, on weeds in full growth. Its efficiency for certain weeds is know if used in good conditions and must be accompanied by crimping. “In our tests, when crimping and defoliating have been made in sunny weather it has increased the efficiency by 20% when used at the recommended dose (16 l / ha). The main problem to this approach is the cost per hectare. A price that is, hopefully, likely to decrease over time.

A Bio herbicide with potential – But at a Price

Another solution is pine oil extract. Marketed in New Zealand and Australia for several years, it is produced in Quebec by AEF Global. Efficiency has been increased by raising the purity of the refined oil. The product has been shown to achieve up to 100% control on some broadleaf weeds and also on some annual grasses. Used at a dilution rate of 10% (on plants at the cotyledon stage) at 20% (on plants over 5 leaves) without addition of adjuvant. Here again the problem lies in the cost which is around 600 € / ha. The product can however find its place in agriculture when used for spot treatment with a jet directed in the row of maize combined with hoeing inter row hoeing. “It can be used in cereals from the five leaf stage of the crop” says Claude Dubois, director of the company, which will launch the product in 2019 in the Canadian market.

In the United States there is another bio herbicide based on fatty acid which interests the organic market. Marketed by the company Westbridge under the name of Suppress, it’s a mixture of caprylic acid and the acid caprique, two fatty acids that it is possible to extract from Goat cheese! On sale for four years it’s been used on several thousand hectares and claimed to be effective on dicotyledons and also on grasses, even in cold conditions. Applied at a dilution rate that varies from 3 to 9% (on average 6% for an application rate of 230lt/ha of water) depending on level of the plants development.

The product is used mainly on fruit trees and vines, taking care not to touch the foliage of crops with a cost of 250 €/ ha. It also has some use in cereals as a pre-harvest biological desiccant but remains a very expensive approach. It is also used on soybeans as an interrow herbicide, with directed applicators which protect the soya foliage. In Argentina it is used in soybean oil production by organic farmers who are trying direct drilling. The key to the products effectiveness is the lecithin contained within the legume that causes a drying effect. Lecithins are complex molecules, phospholipids, consisting in part of fatty acids. “It’s necessary to choose varieties rich in lecithin, while the dilution rate for this is 5%”. Attempts have been made to use it when direct drilling soya into a crimped crop of cereal rye.

A first application is made during the first pass when rolling the rye to create a mulch. While the second application is made after drilling. The product has a residual effect which lasts for ten days allowing the soya time to establish. The oil is not easy to use because it’s hard to mix in the tank of the sprayer and requires constant agitation. Levels of control are in the order of 66% on young seedlings at the 1 to 2 leaf stage, which is very useful for organic farmers. According to producers, sunflower oil could also be used, provided that the varieties are lecithin-rich.

Further products in the pipeline

Finally, another bio herbicide who might have a use for permanent cover crop situations, is a product is called Organo-ground. It consists of a lactic acid bacteria mixture of the Lactobacillus family, which comes from the fermentation of dairy products which produce citric acid and lactic. This product provides partial control of some legumes like white clover or bird’s-foot. Authorized by the Canadian Government, it is currently only available for domestic use under the name of Bioprotec herbicide and the cost is still too high for use on broad acre crops.

“The substance is attractive enough for use in amenity situations but because of the regulatory context in place, this is also limiting its use as a conventional herbicide. Due to its  limited selectivity and its cost it never been marketed widely “ says Claude Dubois, from the company AEF global. He concluded it must be made clear that the development of products based on microorganisms is much easier outside the EU due to the less restrictive regulations. In France, INRA work a lot with the development and potential long term impact of this type product as the effects can take many years to become apparent. Because of this they will take longer to bring to market and therefore be more expensive. This is just a taste of some of the current developments in the bio herbicides arena one thing is certain is that they are likely to be less effective than current synthetic weed killers.

Written by Steve Townsend
Think you have your soil fertility mastered? Well-read on about possibly the most misunderstood soil scientist Dr William
Albrecht, skip this article and you could be missing something

 I don’t think there is anybody in agriculture more misunderstood or misquoted than Dr William Albrecht, who was emeritus professor of soils at the University of Missouri from 1919 – 1959. He began his work in medicine but soon switched to agriculture when he realised that medicine focused on symptoms and not the cause. He reasoned that most health issues were the result of poor nutrition and this could be best addressed by focusing on the soil. He coined the phrase ‘healthy soil, healthy crop, healthy animals’, and we could possibly add to that ‘healthy humans’. Many critics dismiss his work entirely but I believe they are missing the point and that is that crop production is an expression of the soil.

The trouble started, as I see it, when Professor Albrecht allegedly said that the ideal ratio in the soil for calcium and magnesium was 68% and 12% respectively. The wider scientific community took umbrage at this as it threatened the status quo and what they had been preaching on soil fertility. This position still exists today with some scientists saying that Albrecht’s work has been peer reviewed and so doesn’t work or is not relevant. The scientists of this persuasion then set out to prove that this statement was wrong and they found soils could yield just as well without the calcium and magnesium being in these proportions.

This is the crux of the matter. I have read many of Professor Albrecht’s works but not once have I found the alleged statement. He refers to it as the average ratio as you could expect across many different soil types. The ratio he did talk about was that the calcium and magnesium should add up to 80% of the base saturation, then a soil could be considered balanced. Balanced soils he believed gave the most consistent yield and quality, not necessarily the greatest yield at one time. Hopefully that has helped to clear up some confusion and that the Albrecht method of soil testing could have some value to your farm business. Albrecht talked about the soil as a complete entity encompassing chemical, physical and biological attributes.

He recognised that correcting some mineral balances took care of the chemical part of the soil which in turn allowed the physical structure to improve which then provides an environment for the correct biology to flourish. It is a selfsustaining cycle. Of course, like the minerals, the biology has to be there in the first place for it to flourish, it could well be argued that decades of intensive agriculture have depleted our soils to the brink of extinction and the biology may well need re-establishing. Conversely though what this also shows is that there will be little response to ‘bugs in jugs’ if the chemical and physical environment is not there to allow them to flourish.

Exploring Albrecht’s research further, he suggested that there is an ideal ratio between the levels of calcium and magnesium in the soil, which should be related to the soils clay content. While Albrecht did not discover cation exchange he did link cation exchange to the colloidal clay particles within the soil. The clay colloids are negatively charged and have the ability to exchange calcium, magnesium and potassium (amongst many others) for hydrogen with the plant.

Albrecht research initially focused on forage production, and he discovered that calcium was essential in increasing protein content within the forage. He then took this a step further and began trying to relate the calcium content of the soil to the forage and then onto the health of the animal. With this work he found that improved animal health was reflected by the improved forage. This led him on to his hypothesis of the ideal cation ratios in the soil. For the soil he was working on he suggested that the calcium saturation percentage should be 65% and the magnesium should be 15%. But the important point to note here is that the calcium and magnesium percentage should total 80%. Further work by Albrecht and others then suggested that there was a range of ratios depending upon soil clay content. These ratios are where we are today with ideally calcium 60-70% and magnesium 10-20%. Albrecht ignored soil pH reasoning that if the cations are in these ratios the pH will look after itself at around pH6.3

So what does this mean to you?

Many consultants will measure the cation exchange and calculate the calcium and magnesium percentages. A typical result, from a calcareous soil, may look something like this; calcium 84% and magnesium 5% to which you would conclude that all is well. The excess calcium can’t be giving me a problem, after all the calcium is the beneficial element isn’t it and I have low magnesium? But if the calcium level is too high that generally means other cations have suffered as a result. Albrecht discovered that as calcium becomes excessive it ‘masks’ magnesium. In the example above the calcium and magnesium percentages totals 89%, which is beyond Albrecht’s ideal of 80%. If you try to ‘strip’ out the calcium the magnesium level will rise by the corresponding amount. Thus if you lowered the calcium to 70% you would increase the magnesium by 14% to the more accurate figure of 19% which is now a soil with excessive magnesium!

Magnesium in excess is a problematic element in the soil. Excessive magnesium causes clay aggregates to disperse. Clay dispersion reduces soil aggregation in turn reducing pore space (the soil has slumped) and consequently reducing water and air movement. Without air and water movement your soil will no longer have beneficial functioning biology which facilitates nutrient cycling, soil carbon building, and help with soil aggregation to produce the crumb structure and tilth that you need. It has long been known that calcium can ameliorate the effects of heavy soils and their tendency to slump and compact. If your soils slump and compact your crop production will suffer. Your soil will no longer have the pore space to facilitate air and water movement.

But simply adding limestone to correct soil pH using a rough formula based around soil type is imprecise. And what happens if the soil pH is at pH 6.5 or above and there is still a calcium deficiency? I will use the example of a client who had a pH of 7.8, but when the cation exchange was measured revealed a calcium percentage of just 46%. That’s just not possible is it? Well, yes it is, if magnesium and potassium have filled the cation exchange sites they will have a stronger basicity than calcium alone, and result in a high pH.

A simple pH test would suggest that calcium is not necessary, in this situation, and would result in poor crop production (as was the experience in this case), through lack of calcium, poor drainage, low air content and low health soils. Making sure you have the correct calcium content in your soil therefore can’t be achieved by pH alone! Why is this important you might ask? It’s not just about calcium, but blackgrass hates correct calcium & magnesium levels and as mentioned before, producing a healthy soil is difficult without a good balance of these and other elements. If soil health, conservation agriculture or reduced tillage establishment systems are your goal don’t overlook the basics and assume your soil will cope without the right chemical balance. You may be spending money in the wrong areas when a simple soil test will put you on the right track or leave you fighting a chemical imbalance with the cards stacked against you, leading to poor future and present crop performance.

Article adapted from a presentation given by Cotswold Seeds MD Ian Wilkinson at this year’s Groundswell event

In 2016, the NFU reported the biggest year-on-year fall in farm profitability since the millennium, as farmers deal with the impact of devastating cuts in the value of their products and the rising prices of nitrogen fertiliser. There are two ways to increase profit: Intensify to produce more, or lower cost of production with self sufficiency. ‘Farmers should have a low cost of production…be a seller not a buyer’ said Roman statesman Cato back in 234 BC. But how to achieve this?

Free Fertilising

After the Second World War, Sir George Stapledon advocated the ‘dual aspects’ of ley farming. In his book ‘The Plough Up Policy and Ley Farming’ he wrote: ‘Considered as an agent for the promotion of soil fertility, the grass sod must be regarded as perhaps the most valuable foundation upon which the farmer can build.’ In his book, ‘Thirty Years Farming on the Clifton Park System,’ William Lamin recounts how he took over poor sandy land near Burton-on-Trent and made it one of the most productive in the district, giving credit to Robert Elliott, of Clifton Park, who demonstrated how ley farming and rotational grasses helped to build fertility.

A clover rich ley will reliably produce the same amount of nitrogen that farmers typically apply in costly artificial fertilisers. Nitrogen accumulates in small nodules found on clover roots, with some of it being released as the clover plant matures. But after the ley is ploughed in, a large amount of nitrogen is released into the soil and is available over many months. Peak nitrogen availability is around four months after termination, making it available to the following crop which is often a cereal or brassica.

Humus Building

Present day farmer Rob Richmond, who farms light land near Cirencester, has shown how effective ley farming can be for humus building. Twelve years ago soil organic matter on his farm was 2-4%. In 2017 it had risen to 8-9%

Soil Enriching

Data collected by McCance and Widdowson shows the mineral content decline in food over a 50 year period (1940-1991). Levels of sodium, potassium, magnesium, calcium, iron and copper have all significantly dropped in vegetables, milk and meat. Minerals come from the soil and deep rooting plants (ribgrass, chicory, sheep’s parsley, yarrow, and burnet) extract them.

Drought Resisting

The extreme dry conditions this summer have demonstrated the need for drought resistance. Ryegrass has a fibrous shallow root structure and can’t reach down to moisture, but plants in a deep rooting herbal ley can and many farmers have reported that the only crop that’s remained growing on their land this summer is the herbal ley. The best drought resistant species in mixes this year were chicory, sainfoin and birdsfoot trefoil.

Pan Busting

Chicory, with its deep tap-root, also busts through pans to improve the structure of the soil and help water infiltration.

High Yielding

Charles Darwin first noted how different plants grown together yield 50% more than their average, due to their overlapping growth habits and patterns. With some species providing their yield early season and others maturing later, the grazing season is also extended.

Black-grass Suppressing

Long grass leys kill blackgrass. It’s an annual, and doesn’t survive the grass ley part of a crop rotation.

Carbon Capturing

Plants capture carbon from the atmosphere and transfer it to the soil where it’s utilised by the soil biology to help unlock precious nutrients which would otherwise be unavailable to the growing plants. A small increase in soil carbon content can also have a huge impact on its ability to hold moisture, so vital in times of drought. 

A m a z i n g Grazing

A herbal ley (with 30-50% legume content) is more palatable as forage. Livestock eat 10- 15% more and the live weight gain and milk production is improved. Some plants such as sainfoin and birdsfoot trefoil contain condensed tannins in their leaves and stems, which can reduce worm burdens. Charles Hunter-Smart, who farms 2500 acres on the Bradwell Grove Estate, has not needed to worm ewes for two years and didn’t worm any lambs in 2017. 

Crop Rotating

The key to success with a herbal ley is shallow sowing and good seedbed consolidation. For the best results, herbal leys should be left in the ground for four years, giving optium forage yield, root growth, nitrogen fixation and species diversity. Though they are traditionally grazed, herbal leys can also be tailored for cutting for silage (or AD plant) or they may be cut and mulched with a topper.

Put the Big G back into your farming system. Get back on the grass!

Nutrient stratification is common concern for no-till farmers.
By Laura Barrera, first published on
www.Agfuse.com in August 2018

Without tillage to mix fertilizer into the soil, no-tillers may wonder whether the nutrients applied to the soil surface are reaching the crop roots. According to University of Nebraska Extension engineer Paul Jasa and Ray Ward, plant scientist and founder of Ward Laboratories in Kearney, Neb., the resounding answer is: yes, they are. Even though stratification — the non-uniform distribution of nutrients within a soil’s depth, with higher concentrations of nutrients toward the soil surface — does occur in no-till, it should not be a concern. In fact, they say it’s a natural phenomenon and as long as you’re managing your no-till system properly, you shouldn’t have a problem.

Stratification: A natural effect

When you fertilize your pasture, your rangeland or your lawn, how deep do you till it in? That’s the question Paul asks farmers who worry about nutrient stratification in their no-till systems. He asks, if you can put nutrients on top in a natural growing system, why can’t they be placed on top in a cropland system? Ray also points out in native prairies, nutrients work their way down into the soil naturally, just as it occurs in no-till systems. It’s why he prefers to call it nutrient distribution instead of stratification.

In fact, stratification even occurs in tillage systems. “A lot of people who say there’s stratification in no-till have never measured the stratification of their tilled systems,” Paul says, explaining that in his research plots he saw just as much stratification in the disk and chisel systems as he did in no-till. Even as tillage continued, there was actually more stratification in tillage than in no-till. The reason for this is a stronger soil structure under no-till. “The nutrients can move downward with water through the earthworm channels and root channels that are there,” he says. “In tillage, we destroyed those channels so they can’t move downward.”

Soil moisture key for fertilizer uptake

Another reason stratification is not a concern in no-till is because of higher soil moisture, thanks to undisturbed residue. Paul says that when it comes to nutrient placement, there are three rules:

• You have to have nutrients in the soil, because that’s where the roots are.

• You have to roots where the nutrients are.

• You have to have water where the roots are, because the roots need water to uptake the nutrients.

Because tillage dries the soil, there aren’t roots near the soil surface, which means placing nutrients on top of a tilled soil won’t work because there won’t be roots there. But in no-till, if residue is left on top of the soil, there will be moisture, and if there’s moisture, there will be roots. In fact, studies have found that no-tilled crops tend to have greater uptake of surface-applied fertilizer than conventionally tilled crops.

According to a paper written by University of Kentucky soil scientist John Grove, Ward and University of Maryland soil scientist Ray Weil, research conducted in Kentucky from 1980-81 looked at corn’s uptake of surface-applied potassium under moldboard ploughed and no-tilled plots that were established in 1970. Despite the fact that potassium stratification was “substantial and more pronounced” in the no-till plot — 170 ppm for a 2-inch soil depth vs. 132 ppm in the moldboard plowed plot — potassium uptake of the no-tilled corn was 130% of the moldboard-plowed corn.

When the study looked at the total or composite soil test potassium at a 12-inch depth, they found it was nearly identical between the two — 105 ppm for no-till, 107 ppm for the moldboard plough. Scientists concluded “this strongly suggests that the potassium nutrition of the two corn crops was improved by potassium stratification.” Paul’s research also supports that placing phosphorus higher in the soil for corn performs better than phosphorus placed deeper. In 2004, he compared yields between corn that received:

• No phosphorus

• Phosphorus applied with an anhydrous applicator at 5 inches deep, 15 inches from the row

• Phosphorus applied 5 inches deep, 5 inches away on both sides of the row

• Phosphorus applied in-furrow

The corn that received the 5×5 and infurrow placements both yielded around 10 bushels higher than the other two applications, and Paul notes that the 5×5 and in-furrow were statistically the same yield.

“If phosphorus stratification were a problem, putting it deeper should’ve given you a bigger yield,” he explains. “But it didn’t. In the furrow was no problem.” In 2005, Paul tried a few more placement options, including application through a strip-till bar (5×0 treatment), a grain drill to band phosphorus 2 inches deep on 7.5-inch spacing, and phosphorus dribbled on the surface on 7.5-inch spacing. Noting that it was a dry year, Paul found the phosphorus that was banded and dribbled resulted in the highest corn yields.

“That’s because the residue was not disturbed and the fertilizer was right there, so it ran down into the soil and the roots picked it up,” he says. “It just comes down to where are the roots, and is there moisture there for the roots to take the fertilizer up? If the residue is there, there should be moisture.”

Maintain at least 90% residue coverage

Because the roots need soil moisture to absorb fertilizer, leaving crop residue on the soil is key to maintaining that moisture. Paul says he likes to see 100% residue coverage until the crop canopy takes over, but growers need at least 90% to reduce evaporation from the soil surface, according to irrigation engineer Norman Klocke. Why do you need so much residue? Paul says that Klocke gave him the example of an energy-efficient house. If someone leaves the front door open, it doesn’t matter how well-insulated the house is — the heat is going to escape.

Soil moisture works the same way. Too little residue and the water will find a way to escape from the soil surface. For no-tillers whose soils are so biologically active they have a hard time maintaining residue, Paul isn’t too worried about them losing some residue. “Because that residue is being recycled, the nutrients in that residue are becoming available for the next crop,” he says. “So I’m not too concerned about that. Now, if you need it for erosion control or for moisture conservation, that’s where those carbon cover crops become vital.”

Cover crops bring added benefits

While there is some concern that cover crops can use up moisture, Paul says that it depends on your location. But if a grower selects the proper cover crops, he shouldn’t be losing more moisture than is lost to evaporation. “Bare soil evaporation is much higher than people ever thought.” Cover crops can also slow acidification that occurs from surfaceapplying fertilizer, says Ray.

While the calcium-magnesium in corn stalks will help slow it, broadleaf covers contain a lot more calcium-magnesium than grasses, which can help slow it even more. He adds that growers using legumes as covers normally don’t need to apply as much nitrogen to the following cash crop, which also helps slow acidification. But even if soil moisture and acidification aren’t concerns, no-tillers may still want to add cover crops into their systems for their soil health benefits, which in turn improves nutrient uptake.

Ray says that covers help soils get their mycorrhizae established, which does most of the nutrient feeding for the crop roots. “Their threads and hyphae get out and pull those nutrients into the plant,” he explains. “The plant provides the food for the mycorrhizae, so the mycorrhizae can bring the nutrients to the plant. So if you’ve stopped doing any tillage, that mycorrhizae should be developing, and that would be helping nutrient uptake in that topsoil.” He notes that soil health is critical in how plants uptake nutrients, so if a grower hasn’t developed the soil health yet, then the plants may not be able to uptake those nutrients, regardless of how and where the fertilizer is applied.

One warning both Ray and Paul would like no-tillers to heed is the notion that they can heavily reduce or even eliminate fertilizer as their soil health improves. Ray says that aside from nitrogen and some sulphur, which plants can acquire from the air, most nutrients that are removed from the soil will need to be replaced. “When you take something off the land, you take nutrients off,” he says. “So you need to either put that back with manure or compost, or you need to use fertilizer.” The paper by Grove, Ward and Weil recommends ensuring an adequate or slight surplus of nutrition using shallow subsurface placement or surface applications.

Location and crop exceptions

Paul does note that in drier climates, he prefers to place fertilizer in the soil when possible. But as long as there’s adequate residue left, he’s not too concerned, because the moisture should be there to carry the nutrients into the soil. Ray also mentions that areas like the Palouse region in the Pacific Northwest can have dry topsoil from limited moisture, so growers usually put their fertilizer 4-5 inches deep in the soil where moisture is still available. “Now we’re doing no-till, so that’s changed that dynamic some,” he says.

Farmers growing crops that are sensitive to residue also may need to adjust their fertilizer strategies, Paul says. Canola in particular, he explains, is sensitive to too much residue because the canola seedlings are so small. “Canola tries to get above the residue. It’ll grow real fast, have a long stem there, and the frost can kill it.” His recommendation to farmers growing canola and other residue-sensitive crops is to put some fertilizer down in a starter application during planting. “I’m a firm believer in starter fertilizer being placed down in the soil with the seed to get that crop started,” he says. “Because in those early first couple weeks of growing, roots aren’t out there in the row middles where the residue is protecting the soil or keeping the moisture there.”

So if a no-tiller is running row cleaners on his planter to push the residue away, it’ll provide a bare strip of soil that will warm up and dry out. “When it dries out, the nutrients better be in the soil itself there,” Paul says. Don’t change your soil sampling strategy Despite some suggestions that no-tillers should be soil sampling at shallower depths because of stratification, when it comes to taking soil tests for fertilizer recommendations, Ray does not recommend no-tillers do anything different. The reason for this is due to how the soil tests are calibrated. While in Nebraska the tests are calibrated for an 8-inch depth, in most states it’s a 6-inch depth. If a grower submits a sample that’s at shallower depth, the calibration will be off, Ray explains.

And because the nutrient concentration is higher at the top, he may get a lower fertilizer recommendation than what is needed and end up under-fertilizing his crop. “The roots grow down 4 to 6 feet deep in the soil,” Ray says. “So we’re estimating from the top 6-8 inches of soil what that plant needs, when it’s growing 4 to 6 feet. So if you start sampling different depths, you’re going to get a different reading than if you were to sample 0 to 6 inches or 0 to 8. “I don’t encourage different sampling, if I’m trying to interpret fertilizer recommendations.”

Jamie Stotzka, Consultant Bioagronomist

Healthy soils contain billions of bacteria from thousands of species. A special group of these bacteria, collectively known as Plant Growth Promoting Rhizobacteria or PGPR are known to promote plant health, growth and productivity. PGPR are unlike the nodulating rhizobia only found associating with leguminous plants, as they are free-living in soils residing in the plant root zone whilst also having the ability to enter plant tissue. Nourished by plant exudates, these bacteria provide indispensable services to growing crops.

PGPR’s plant growth promoting effects can be attributed to four main mechanisms: enhanced nutrient delivery, protection of plants from potential pathogens, improved root development and the bioremediation (cleaning) of soils. Probably the most renowned trait of these bacteria is their ability to fix atmospheric nitrogen. Over 78% of the atmosphere is gaseous N2, which is ordinarily unusable by plants. A unique set of enzymes allows PGPR convert this gas into plant useble NH4+. Above each hectare of land, approximately 74,000 tonnes of N2 are within reach to be converted by this process.

Another macro element phosphorus can be present in soils but is often-times ‘locked up’ – i.e. bound to metal elements. PGPR act to solubilise this element by producing organic acids and inconcert with other soil microbes this community has the capability of increasing available soil P by up to 62%. Other essential nutrients are also chelated by PGPR. Working in tandem with other beneficial soil microbes, such as arbuscular mycorrhizal fungi (AMF), these nutrients can be efficiently transported to crops in healthy soils. PGPR can further alter the root architecture and promote plant development via the production of phytohormones such as auxins, cytokinins and gibberellic acid. Plant protection is achieved by regulation of plant internal defences against drought and pathogens.

The positive effects of PGPR have in the past been assumed to be fairly generalist and to apply to a broad range of crops. Commercial inoculants have been available for a number of years to improve plant health and development in arable systems. Most of these products operate under a “more is better” policy and fail to discriminate between the particular effects of different bacterial species on particular crop types. In trials over the past three years, researchers at PlantWorks Ltd have found that this one-size-fits-all approach may have drawbacks and hidden pitfalls.

A range of bacterial species produced by the company were tested in isolation on different crop types, with significant results. Yield results indicated that even within the cereals group, plants did not necessarily share the same ideal bacterial partners. Field trials were established based on outcomes from preliminary glasshouse experiments and in 2017 these produced very encouraging results.

A sugar beet trial run in collaboration with Allpress Farms in Cambridgeshire, which utilised a tailored beet inoculum, produced a statistically significant yield increase of 33% with no reduction in quality of the roots. Potato and field vegetable trials showed similarly positive and significant trends with i.e. 43% heavier leeks produced at Allpress. * Average grain weights on Motts Farm in Essex. Measurements were taken from random quadrat readings taken throughout treated and control areas (PlantWorks, 2018). Previous trial work at Mr Cowell’s farm revealed that through no-till and low input farming systems, as well as rotations including mycorrhiza friendly plants such as Lucerne, the soils were highly biologically active. With wheat on the farm showing very high mycorrhizal colonisation levels of up to 80%. This background fungal network was thought to have further enhanced and supported bacterial function to achieve the positive yield noted. This hypothesis was further illustrated by PGPR trials at GH Dean in Kent.

Here, mycorrhizal and bacterial inoculants were applied in isolation and combination, revealing a positive interaction between the two types of microbes. A tailored selection of bacterial inoculants for a range of cereal crops has now become available within the PlantWorks’ Smart Rotations range. Applied in liquid form these tailored PGPR consortia are easy and straightforward to apply using standard sprayers. Further products to enhance mycorrhizal communities in farm soils can be added within crop rotations to build strong fungal communities to support bacterial function.

It is clear that the inclusion of biological inoculants such as PGPR and mycorrhizal fungi has vast potential to allow for more sustainable crop production with possible savings in mineral fertilisers, the use pesticide products as well as building healthy, balanced soils. It is an exciting time within farming, with a growing database of knowledge, ever more sophisticated advice and well tested products becoming available farmers can now, very practically, intervene within rotations to increase beneficial soil biology to enhance arable yields. For further information contact Ms Jamie Stotzka , Consultant Bioagronomist, PlantWorks Ltd. Office: +44(0)1795 411527 e-mail: jamie.stotzka@plantworksuk.co.uk http://smart.plantworksuk.co.uk/