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Written by Natallia Gulbis, Technical and Arable Farming Lead at PlantWorks Ltd

According to the European Biostimulants Industry Council, a biostimulant is a material that contains substances and/or micro-organisms whose function, when applied to plants or the rhizosphere, is to stimulate natural processes to enhance/ benefit nutrient uptake, nutrient efficiency, tolerance to environmental stress and crop quality. Within the increasing number of companies, both manufacturers and suppliers, offering microbial based biostimulants into UK agriculture PlantWorks Ltd, based at the Kent Science Park and NIAB EMR, has one of the longest scientific programmes that has sought to refine consortia of beneficial bacteria and Mycorrhizal fungi and trail them across the UK. Here Natallia Gulbis, Technical and Arable Farming Lead at PlantWorks Ltd talks about the last two years’ of trials.

Founded in 2000, as a spin out company from the university of Kent, we are the UK’s only mass producer of Mycorrhizal fungi (MF) and a producer of Plant Growth Promoting Rhizobacteria (PGPR) since 2014. PlantWorks has built a reputation as a technology-led company with established markets in many areas of horticulture. In 2014 the company commenced the development of a liquid based PGPR biofertilizer to complement the Mycorrhizal fungi range for the agricultural market. We are now five years through this journey and have developed a range of PGPR based products for both cereal and vegetable crops. During this time, we have continually developed the products to optimise performance and user experience including formulating the products to best suit the crop, increasing our understanding about application methods of the technology and how different rotations effect their performance.

One of the major milestones to come from our research to date has been to confirm that more, in terms of diversity of strains of different bacteria, is not always better, in fact the converse can be true

A significant series of experiments showed that a crop specific tuned consortium of bacteria performed best in terms of yield and nitrogen use efficiency. This research underpinned the formulation and launch of the SMART ROTATION 3 range of bio-fertilisers that have been trialled extensively in over 70 trials in the UK over the past 2 years, much of this work undertaken in collaboration with the UK’s major agronomy companies and research institutes serving applied agriculture. 

The body of data collected from these trials now enables us to apply rigorous statistical methods to determine the value-added effects of applying SMART ROTATIONS 3 in your field. Mixed linear modelling is a statistical method that estimates mean values across large datasets taking into account fixed (e.g. treatment with PGPR) and random (e.g farm) variables. Using this method across 534 data points collected over 2 years of trials across 3 arable crops grown on 12 different farms across the country the model has shown that application of PGPR gives a 10.5% increase in ear count and a 5.6% increase in yield compared to untreated controls (figure 1). When broken down by crop yield increases are estimated to be 8%, 7.5% and 2.9% for barley, oat and wheat respectively.

* NB The estimated means displayed in these graphs are a combination of oat, wheat and barley data combined and therefore do not reflect the absolute yield you would expect for any one of these crops. The figures quoted for ‘ear count’ and ‘yield’ are baseline figures with all other factors, other than the addition of SR3 (plant growth promoting rhizobacteria), removed and therefore these figures do not represent actual ear counts and yields

In 2020 we will focus on research that will seek to improve the application of the technology with a particular focus on increasing the bio-fertilisers ability to enter the root zone efficiently and consistently in all weathers. Where previous work had sought to challenge the technology across many crop and soil types this work will focus on two ‘monitor’ farms in Kent and Cambridgeshire and will enable us to offer further knowledge on how best to use this exciting technology.

The liquid bacteria products are sold under the SMART ROTATION 3 brand name and are supplied as liquid cultures and sprayed to ground after drilling and for winter crops applied again in Spring. Currently the products are sold in units sufficient to treat 5 hectares and are simply added to the spray tank, set for course droplets, with a recommendation of 200 litres of water applied per hectare. Products are tuned and available for wheat, oats, barley, OSR, sugar beet, potatoes & carrots and leek & onions.

In an regulatory environment where the use of chemicals, whether they be fertilisers or pesticides, are being restrained, as we rightly focus on the long term health of our soils, the use of biofertilisers are increasingly seen by many as a technology that will be adopted as common practice in the years ahead. There is a considerable body of research being undertaken in the UK throughout the university sector on the role of microbes in enhancing crop efficiency and we are one of a number of pioneering companies that are ‘tuning’ the technology for real life application.

About PlantWorks

PlantWorks is a leading agricultural and horticultural research firm that specialises in sustainable, natural plant growth solutions. Based at the Kent Science Park and NIAB EMR, PlantWorks has a core science team embracing the disciplines of soil biology, bacteriology and plant science. PlantWorks is one of the largest manufactruers of mycorrhizal fungi in Europe and produces five well characterised strains within its controlled growing facilities split between East Malling Research and Kent Science Park. PlantWorks maintains a large collection of Plant Growth Promoting Rhizobacteria (PGPR) that it routinely cultures and formulates in support of farming trials and new product offerings.

Written by Steve Holloway from Soil Fertility Services Ltd

A soil test will give you numbers and guidelines of where your soil is and hopefully where it should aim for to consider it ‘balanced’ (note I didn’t say healthy); remember that it’s NOT an N-P-K world. Sensible soil nutrition is the first step toward higher crop quality and yields. Testing will measure levels of various elements within the soil such as Calcium (C) and Magnesium (Mg) which are two of the main building blocks of soil aggregation; high levels of either will have a negative effect of how well the soil functions. Mulders chart shows the interactions of soil nutrients (how one nutrient influence another), for example – too much nitrogen can reduce the plant’s ability to take up Potassium, Boron and Copper increase Potassium and reduce the availability of Magnesium.

This effect is known as antagonism. Calcium is a bit of a bully in the soil where antagonism is concerned; when levels are high Manganese (Mn), Magnesium (Mg), Potassium (K), Phosphate (P), Iron (I), Boron (B) and Zinc (Zn) are all affected. However, calcium is needed in plants as a building block and is vital as the ‘cement’ that holds cells together and produces stability for plant cell structure. Silica, although not readily plant available from within your soil, is also important for increasing the physical strength of plants and in turn the plant’s natural resilience to pest and disease pressures.

Having established a soil test shows the mineral makeup of your soil and a specific number of anions/cations relative to the elements measured, from there you can identify where your soil sits when compared to the ideal’ target range. But is that a healthy’ soil?

Many of the measured elements will not yet be available to your crop, if they were, the greedy plants would gorge on this deluge of goodies and make themselves sick while most unclaimed nutrients would volatilise or be washed away. It has to be a balancing act of what’s available and what can be ‘made available’. Within the soil, various elements hold onto each other, dictated by whether the element is positively charged (cation) or negatively charged (anion). This is how nutrients are ‘locked up.’ These bonds can be broken by the root microbes or by the environment. Humic and Fulvic acid are referred to as chelators; they improve the delivery and efficacy of foliar applied nutrients, forming strong bonds with trace elements and enabling the direct uptake of nutrients across the plant leaf with reduced risk of leaf burn.

When bonded with Humates, applied nutrients are kept plant available in the root zone, reducing nitrogen leaching and phosphorus lock-up.

Imagine how much healthier your soils could be with the addition of Humic acid. With a cation exchange capacity (CEC) of 300-500, an increased available water capacity up to 30-50% more, on top of that you get improved soil quality due in part to increased activity of the beneficial bacteria building better soil aggregates. Biological activity plays a key part in the soil/plant relationship and as such trades commodities with the plant, releasing tied up nutrients for plants to utilise. So, you could say the numbers in a soil test mean very little if you don’t have ‘the biological army’ around the root to support and maximise nutrient availability. A healthy soil will have balance; excesses and deficiencies – physical or biological can have a negative influence. Measuring and monitoring your soil and plant on a regular basis will highlight potential problem areas, for example: you test the soil and are low in (x) but when you test the plant you are not low in (x) is there an issue? 

You get the lab to test for biological activity, and a result comes back with a high rating, so is everything ok? Are those organisms beneficial? What percentage? A decision made with blinkers on is not a decision it’s a leap of faith! Longer term assessment must be a part of your farming system; know your history to plan your future, be prepared to throw the rule book out the window. The soil test doesn’t tell you what’s in the plant, the plant analysis doesn’t tell you what is in the soil – you need both.

Soil Fertility Services was established in the 1990’s and has since been working hand in hand with farmers throughout the UK, constantly striving to find biological farming solutions that are efficient and more effective, in order to build soil fertility and provide crop nutrition.

Written by Keith Diedrick, Area Agronomist at Corteva USA

Summary

• Soil testing is a useful and relatively inexpensive management tool for growers to assess crop nutrient levels in their fields. 

• Proper methods and timing of soil sampling help ensure reliability of test results for making informed decisions related to soil inputs such as fertilizer and lime. 

• Standard soil tests typically evaluate pH, buffer pH, organic matter, cation exchange capacity, phosphorus, potassium, calcium, magnesium and base saturation. 

• Micronutrient soil testing alone is generally not a reliable tool to predict potential micronutrient deficiencies. Tissue testing, soil properties, and growing conditions together are a more complete diagnostic approach. 

• Critical levels of nutrients (the point below which crop yield may decrease quickly) and crop removal rates are useful for determining the rate and frequency of fertilizer application to a field.

Growers must efficiently manage field inputs while reducing the risk of yield losses to maximize profitability season after season. Fertilizers are significant variable costs in production, and tools are available to assess their need.  

Soil Testing – Selecting a Laboratory

Competent analytical laboratories use strict standardized methods in controlled environments with quality standards; all of these are important to reliable and comparable data for informed decision making in the field. A number of commercial labs exist and some land-grant colleges have labs as well. Growers may benefit from a review of considerations and tips for selecting a soil testing laboratory (Diedrick, et al. 2010).

Soil test kits and strips found at garden centers are not a replacement for a professional testing laboratory analysis due to the risk of high variability and questionable precision. A good laboratory test report is a small investment compared to the magnitude of fertilizer and lime investments by an operation. Once a laboratory is selected, a quality sample must be collected and handled correctly for an accurate analysis.

Sample Collection

Regardless if the sampling plan is random or part of a precision management system, collecting and submitting a clean and representative sample is required for reliable results. Below are some best management practices for obtaining representative samples for analysis.

• Soil sample every 2 to 4 years for a given field; sampling every year rarely adds additional information. 

• Sample when crops are not growing in the field (applies to standard soil sampling). 

• Avoid fields where fertilizer, manure, or liming materials were recently applied. 

• Sample fields at the same time

every year so that analyses are more comparable over time. Sampling 3 to 6 months prior to the next crop will allow enough time for any pH or nutrient adjustments. For many crops, this time is post-harvest in late autumn.

• Thoroughly clean the soil probe or instrument to remove all residual soil or debris. It does not take much of a foreign substance to significantly contaminate a sample.

• Be sure the sampling container is similarly clean to prevent any contamination. Plastic or stainless steel containers are preferable to other materials.

• Move residue, debris, and any vegetation from the soil surface at the sample site. Failing to do so will cause an incorrect (too high) organic matter measurement.

• Pull soil cores from a depth of 6 to 8 inches, or depth to plough layer where soil mixing occurs. Long-term no-till fields, perennial forages, ridge tillage, and similar systems may be sampled also at a shallower depth to note any shift in soil pH in the top 2 to 4 inches.

• Obtain 15 to 20 soil cores for an area of 20 acres or less. For larger areas, submit multiple samples for more accurate soil information, even if the field appears uniform.

• Mix cores together well for the sample. Usually, samples can be sent moist after mixing. For standard soil tests, air drying is permissible, but do not heat cores to speed drying.

• Follow the soil laboratory’s instructions for submission, using the containers recommended or supplied by the lab.

A Typical Standard Soil Test Report

Most laboratories offer a “standard soil test” which covers a set of soil chemical measurements that are important in agronomic decision making. Though some labs vary, typically this includes pH, buffer pH, cation exchange capacity (CEC), base saturation, organic matter (OM), and the macronutrients phosphorus (P), potassium (K+), calcium (Ca2+), and magnesium (Mg2+). In the Plains and western regions where salinity and sodicity are more common, conductivity, soluble salts, sodium (Na+) and chloride (Cl-) may also be reported in a local laboratory’s standard test. Nitrate (NO3-) and sulphur (S), are not usually part of standard tests, but are considered macronutrients. Nitrate tests are used in some regions for preplant nitrogen (N) management and in-season sidedress decisions, but recommendations vary from region to region.

Test Values Explained

pH is the measure of acidity of a substance. pH is expressed as a number, not a percentage or other quantity. A value of 7.0 on the pH scale is considered neutral, that is, the substance is neither acidic nor basic. Lower numbers on the pH scale denote increasing H+ ions and acidity. The acidity of the soil solution affects many physical, chemical, and biological reactions necessary for plants to survive and thrive. The optimum pH value varies by crop and region, but is generally between 6.0 and 7.0 pH (slightly acidic), though alfalfa thrives between pH 6.8 to 7.0.

Buffer pH – Once a need for adjusting pH higher is identified, the buffer pH value indicates the amount of liming material necessary to make the adjustment. Low buffer pH values indicate that more lime materials are necessary to raise pH than higher buffer pH values. “Buffering” in this case refers to the ability of the soil to “recharge” acidity, and is a function of aluminium (Al3+) minerals and H+ in the soil (and is related to CEC). If a soil is poorly buffered (sandy), less liming material are needed to raise pH a certain level than a soil that is highly buffered (clayey soil). Some soil tests may report buffer pH as lime test index, or LTI, which is merely the buffer pH value multiplied by 10.

Organic Matter – Expressed as a percentage, OM is the non-mineral content of the soil sample and is usually determined by combustion. Organic matter has many functions, including water-holding capacity, nutrient cycling, and contributing to soil structure and CEC 

CEC – Cation Exchange Capacity is measured in milliequivalents per 100 grams of soil. CEC is determined primarily by soil clay mineralogy and OM level in the soil. Cation exchange capacity represents a measure of electrostatic charge sites in the soil that can hold cations, or positively charged ions, like Ca2+, Mg2+, Mn2+, Zn2+, K+, H+, and Al3+.

For each “equivalent” charged site on the soil particles, a single positive charge can be held (denoted by the superscript number on these ions). In the case of K+, a K+ ion has a single positive charge, and is held by one CEC site. For a Ca2+ ion, two CEC sites are necessary to hold one Ca2+ ion, three CEC sites for Al3+, etc.

Higher CEC values in soil represent more capacity for nutrient cations to attach. For example, a high CEC soil can theoretically hold many K+ ions, but would require more K+ to be applied as fertilizer to fill the sites located on the soil particle surfaces before it is easily released to the soil solution and taken up by plants

P – Phosphorus is reported in parts per million (ppm) or pounds per acre (1 pound per acre = 2 parts per million). This is not a measurement of total P in the soil, however, it is an estimate of P that is available to plants. The testing procedure utilizes an extractant that is correlated with P uptake that might occur by plant roots. This value is reported on the soil test as “extractable P.” Not all labs use the same process; some may use the Bray-Kurtz P1, Mehlich III, Olsen, or other procedure. Reported P values will vary according to the test procedure and are not directly comparable to each other.

P is an important element in plants, as it is part of the DNA, RNA, the energy transfer molecule ATP, as well as amino acids and proteins.

K+ – Potassium is reported as ppm or lb/acre of “exchangeable K.” Like P, all of the K+ in a soil sample is not available to the plant. Most of the K is locked in mineral structures, some is available slowly from the clay edges, and other K+ ions may attach to the CEC (exchangeable) and flow easily to the soil solution. The K+ extraction solution measures K+ that can be readily moved from the CEC and into soil solution, simulating the processes that might exist with a root system in the soil

Potassium is vital in water regulation and enzyme activation in plants. Plant stomata, which are openings in the leaf used for gas exchange, open and close by movement of K+ in and out of the cells surrounding the opening. Potassium (and other nutrients) in plant stover or residue on the soil surface can cycle back to the soil with rainfall events and residue breakdown (this sometimes includes up to 80% of K in residue). If little to no rainfall occurs after harvest prior to soil sampling, the reported K+ value may be lower than expected because of this lack of cycling. Dry conditions also limit the movement of slowly available K+ to the CEC.

Ca2+ – Calcium content of the soil is reported in ppm or lb/acre, sometimes listed as “exchangeable calcium.” Calcium is a common element in a lot of mineral soils, and though they may occur in some regions, deficiencies are rare in most soil environments above pH 5.5. The easiest correction to a suspected Ca2+ deficiency is raising soil pH with a liming compound, and Ca2+ is considered sufficient at ≥200-300 ppm. Calcium is essential to plant cell wall structure, cell division, and many enzymatic processes.

Mg2+ – Magnesium levels are measured in ppm or lb/acre, sometimes listed as “exchangeable magnesium.” Magnesium is a key element in chlorophyll and many enzymes and enzyme activation. Deficiencies can occur in crops, and can be remedied with Mg-containing fertilizers or dolomitic limestone. Mg2+ is sufficient for most crops at ≥50-100 ppm.

Base Saturation – This is a description of the major cations held on the CEC on a percentage basis. Typically, Ca2+, Mg2+, K+, and H+ are listed (and sometimes Na+ and Al3+) as they are of the highest concentration. Other cations may attach, such as the metal micronutrients, but they are often measured in ppm, not a percentage (1 ppm = 0.0001%) The percentage of H+ is related to the buffer pH value discussed earlier. When H+ moves off of the CEC and into soil solution, the solution becomes more acidic. The portion of H+ on the CEC is sometimes referred to as “reserve acidity.

Base Saturation Ratios

There is a long-standing debate on the usefulness of base saturation for determining lime and fertilizer rates, particularly the Ca:Mg ratio. There is a lack of evidence that a certain ratio of bases is necessary for optimum crop performance. A large body of research shows that if nutrients are in the soil at high enough levels and pH is in the proper range, optimum yields in agronomic crops can be achieved across a wide range of Ca:Mg ratios.

There are a few ratios of note for specific crops and soils, however. The ratio of Mg:K is of importance to forage growers. If excessive K+ is taken up by the plants and Mg2+ is low, the forage may contain low Mg2+ content and cause a metabolic condition in livestock called grass tetany (hypomagnesemia). Dolomitic limestone and Mg-containing fertilizers are options, but supplying feed additives with Mg to livestock may be more economical. 

When Mg2+ exceeds Ca2+, or when Na+ becomes high (>15%), this may be indicative of possible soil structural issues, such as clay dispersion or flocculation, surface sealing, and decreased water infiltration. This is most likely to occur in areas of naturally occurring Na+ and Mg2+, but these are not widespread in North America.

Soluble Salts – The soluble salt content (or conductivity) is expressed in dS/m or mmho/cm (which are equivalent). If soluble salts are too high in the soil, plants cannot take up sufficient water, wilt, and in severe cases, die. In most crops, performance and yield decline rapidly at 3 to 4 dS/m and higher, and may be affected as low as 2 dS/m.

Salt problems are a concern primarily in the Plains and western regions of North America where various salts are native to the soil in high levels. Some effluent irrigation waters and fertilizers have the potential to cause salt problems as well, most notably muriate of potash (KCl; 0-0-60) and urea (46-0-0). Use extreme caution when applying in-furrow or banding.

Micronutrient Soil Tests

Notice that standard soil tests typically do not include elements like manganese, boron, zinc, iron, and copper. At this time, it is difficult to correlate micronutrient levels in the soil with crop response. Plants require very little of these micronutrients to thrive and the exact required amount can be difficult to ascertain. The challenge for researchers is to reliably correlate a soil test level with plant uptake (like P and K). Even if this was known, the relationship to test level and crop response is similarly variable.

To further complicate micronutrient predictions, the availability of micronutrients can vary with soil physical characteristics which change during the year (moisture, aeration, microbe activity, etc.). If soil test levels of a micronutrient are high, crop responses to fertilization of that nutrient are unlikely. If a micronutrient level is marginal or low in the soil, the crop still may not respond to a micronutrient application. Additionally, not all crops have the same sensitivity to particular micronutrients. Knowing the soil, crop sensitivity, and environmental factors that may cause a nutrient deficiency is helpful to gauge risk and prepare appropriately (Butzen, 2010; Diedrick, 2010; Jeschke and Diedrick, 2010).

Choosing Fertilizer Rates

A starting point in nutrient management decisions is comparing soil test results to established critical levels for the particular crop. Critical levels are the point where yield loss potential increases quickly if soil test levels for a particular nutrient fall below that level (Figure 2).

These established critical levels may vary from region to region, but recent research shows that critical values are close to the ranges in Table 1.

1 Critical level for ppm K = 75 + (2.5 x CEC) for all crops

2 Values in parentheses are lb/acre.

3 Several sources do not cite CEC specific K, and may vary. Consult your local Pioneer professional for additional local information.

One strategy that growers may adopt is to build soil test levels just above the critical levels and apply nutrients to annual or biennial crop removal rates. This accounts for variability in fertilizer spreading as well as assuring soil test levels over critical levels for anticipated crop removal. This practice may guide appropriate fertilizer rates for rented land or when fertilizer prices are high while still reducing the risk of yield loss. Approximate crop removal rates are below; these values may vary by year and growing environment.

Adapted from Warnecke, et al., 2004; IPNI, 2010.

1Based on Pioneer research. Fertilizer products will have an analysis printed on the bag or bin that identifies the amount of N, P, and K contained in the product. This is widely done with three numbers arranged as N-P-K. The N value on the tag is simply a percentage of N, however, P and K are listed as P2O5 and K2O.

Crop removal and fertilization are activities that change soil test levels of nutrients. Depending on the buffering capacity (CEC) and soil mineral composition, the amount of P2O5 and K2O necessary to change soil test P and K will vary and in some cases, be difficult to predict. Research from Kentucky (Thom and Dollarhide, 2002) shows that for low levels of soil test P, more P2O5 fertilizer is required to change the levels than at high soil test P levels >100 ppm (Table 3).

To change K+ test levels by 1 ppm, K2O additions may range from 2 to 6 pounds per acre, again, depending on existing K+ levels, soil minerals, and CEC.

Conclusions

Soil testing is an inexpensive practice to learn about the ability of soils to support crop growth. With knowledge of what each soil test value means, growers can make more informed crop input decisions to minimize risk and maximize profitability.

References and Further Reading

Butzen, S. 2010. Micronutrients for crop production. Crop Insights. Pioneer Hi-Bred Int., Inc., Johnston, IA.

Cornell Univ., 2010. Northeast Region Certified Crop Advisor study resources. Competency area 3 – soil testing and plant tissue analysis. 

Diedrick, K.A. 2010. Manganese fertility in soybean production. Crop Insights. Pioneer Hi-Bred Int., Inc., Johnston, IA.

Diedrick, K.A., G. Gao, R.W. Mullen, and M.E. Watson. 2010. Choosing a soil analytical laboratory. OSU Ext. Bull. HYG-1133. Ohio State Univ., Columbus, OH. [Online

Havlin, J.L., J.D. Beaton, S.L. Tisdale, and W.L. Nelson. 2005. Soil fertility and nutrient management: an introduction to nutrient management. 7th ed. Pearson/Prentice Hall. Upper Saddle River, NJ.

International Plant Nutrition Institute. 2010. Nutrients removed by harvested portions of crop. IPNI, Norcross, GA. 

Jeschke, M. and K.A. Diedrick. 2010. Sulfur fertility for crop production. Crop Insights. Pioneer Hi-Bred Int., Inc., Johnston, IA.

Kansas State Univ. 1998. Grain sorghum production guide. K-State Res. and Ext., Manhattan, KS.

Kansas State Univ. 2009. High plains sunflower production handbook. K-State Res. and Ext., Manhattan, KS.

Seelig, B.D. 2000. Salinity and sodicity in North Dakota soils. NDSU Ext. pub. EB-57. North Dakota State Univ., Fargo, ND.

Thom, W. and J. Dollarhide. 2002. Phosphorus soil test change following the addition of phosphorus fertilizer to 16 Kentucky soils. Univ. of Kentucky Coop. Ext. Agronomy Notes, 34(2). Lexington, KY.

Vitosh, M.L., J.W. Johnson, and D.B. Mengel. 1995. Tri state fertilizer recommendations for corn, soybeans, wheat and alfalfa. Ext. Bull. E-2567. Michigan State Univ., Ohio State Univ., and Purdue Univ.

Warncke, D., J. Dahl, L. Jacobs, and C. Laboski. 2004. Nutrient recommendations for field crops in Michigan. MSUE Bulletin E2904. Michigan State Univ., East Lansing.

The future to understanding soil health lies in a tool that can sniff the gases produced by the soil’s microbial life.

You can’t optimise what you can’t measure, and the vital activities of microbial life in the soil are currently difficult to measure outside of a specialised academic laboratory. P.E.S. Technologies is therefore using cutting edge semiconductor technology to develop a sensor that can quickly assess soil health using a simple hand-held sensor out in the field. The sensor “sniffs” the soil to detect all the various gases produced by the soil’s microbes. By using artificial intelligence the soil health analysis system can learn what the different smells mean and give greater insight, on the spot, into soil health than current tests to asses soil biology.

The journey of getting your soil into a really good condition often starts with switching to no-till practices. But beyond that there are decisions upon decisions that need to be made to regenerate soil biology from choosing the best crop types to have in your rotations to which cover crops to plant. Additionally, there are a whole host of exciting new biostimulants to try out as well as reductions in nitrogen fertiliser applications that can be explored. Further, with nematicides disappearing from the market, optimising biofumigation processes that produce gluconsinolate gases in the soil to control PCN may become a priority in future.

But each farm is unique and what works best on one farm may not work best on another. So, the first step to managing soil health should be to measure it and then monitor changes over time as they occur depending on changes to management practices. However, currently the tools available to assess soil biology have limited capabilities and there are only a few to choose from.

To make the right agronomic decisions to optimise a farm’s soil health in the most cost-effective way for each farmer, a tool is needed that makes soil health assessments easy, affordable, quick, and comprehensive. On top of all that, data is needed that doesn’t become obsolete the minute soil scientists make new discoveries that change our understanding of what a healthy, functional soil is.

While huge strides are being made in the field of DNA analysis, the samples still need to be sent off to a laboratory and the costs per test are very high. Therefore, most currently used tests for monitoring soil biology rely on gas sensing—but they only sense one gas, namely CO2. P.E.S. Technologies have instead developed a sensor that can profile all the soil’s gases with a hand-held device that can be used in the field. In other words, we “smell the soil” on the spot. This allows us to assess soil health easily, quickly, and comprehensively.

P.E.S. Technologies soil sniffer is hand-held, battery powered, and linked to a smart phone via Bluetooth. For each test, a soil sample should be taken from the top 20 cm of soil and placed into a small drawer in the device. Importantly, no other preparation of the soil sample is required. This means that each test can be completed in only 5 minutes. The agronomist or farmer never has to see the complicated smell patterns, all you get to see on the phone is the important information that is pulled out from that data: a soil health score and the various soil health indicators (for example, microbial biomass, nitrates, and pH amongst others) that are used to assess the health of the soil.

Soil gases are currently an underappreciated resource: they provide a wealth of information on soil conditions as specific microbial activities are associated with different gas patterns. As an example, microbes that are converting between the different forms of nitrates in the soil produce different gases that can then be linked to the concentration of nitrates in the soil. Additionally, bacteria and fungi give off distinct gas patterns, while different bacteria may flourish in well-aerated soils with good drainage compared with compacted soils.

Each soil test requires a single-use sensor strip, which is what detects the gases. This unique test strip was invented by Dr Jim Bailey, founder of P.E.S. Technologies and previously a semiconductor physicist at Imperial College London. Another key aspect of the sensor system is that is that the system learns and provides better results over time. It does this by analysing the raw gas data in the cloud using artificial intelligence. The same way you can train a dog to understand the meaning of more and more smells, the artificial intelligence software can be taught to do the same. The test is therefore futureproof. A simple software update can expand its capabilities and data collected in previous years can simply be reanalysed.

This is future tech, but it is not that far off being on the market! Already, P.E.S. Technologies was able to demonstrate the feasibility of sniffing soil with its sensor technology for soil health monitoring purposes by working with experts in the field in a government funded project (Innovate UK project number 133537). A further three Innovate UK funded projects (project numbers 105534, 105664, and 105668) are currently under way to help fully train the soil sniffer software and get it into the hands of agronomists and farmers by 2021/22. This soil health data will allow better land management decisions that will help improve soil health faster and more efficiently: after all, you can’t optimise what you can’t measure!

While the technology is not currently scheduled to be released until around 2021/22, suitable test sites are currently being sought and an early-release version is currently being considered. Farmers and agronomists can register their interest at pestechnologies.com/ register.