Sulphur blends A manageable solution for enhancing yields

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1 SEPTEMBER/OCTOBER 2015 Sulphur blends A manageable solution for enhancing yields York Potash Project Fertilizers FOCUS Europe SEPTEMBER/OCTOBER AGRA in 2015 Africa

2 Technological advances in nitrogen use efficiency How does this affect value? By Brian Wade, PhD, Koch Agronomic Services Technological improvements in nitrogen use efficiency are a clear path to value creation for the fertilizer industry and provide opportunities for all players in the value chain, from manufacturer to farmer. Reducing the amount of nitrogen lost enables opportunities to multiply its value through increased crop yield (or elimination of over-application). The surging interest and use of proven, registered technologies is evidence of industry-wide focus on value creation through nutrient efficiency. In the past, the job of the fertilizer industry was considered finished once fertilizer was applied to the field. Working backwards from the time of application: the fertilizer product was sold, distributed and manufactured all are processes that the industry does efficiently. But, working forward from the time of application there are many improvement opportunities: Is nitrogen fertilizer a substantial component of the crop value? What is it worth? What technologies have been proven to improve nutrient efficiency? What is the regulatory status of the technologies within the legislative framework of the European Commission? This article highlights a point of view regarding value creation opportunities, the technologies to achieve the opportunities and highlights some of the evidence to validate the technologies. For comprehensive details the reader can refer to publications from Trenkel 1 or others. Nitrogen: Both a value creator and a value enabler Of the various crop inputs, nitrogen fertilizer alone is likely the single largest contributor to final crop yield. Other individual crop production inputs and practices simply do not have as much impact. The only other factor with more effect than nitrogen is the weather. The crop yield pyramid in figure 1 illustrates the dominant role of nitrogen input. The pyramid is derived from the research on maize by Dr. Fred Below 2 and colleagues using the omission plot trial design to rank and specifically quantify the individual contributing factors to the accumulated maize yield (see figure 1). An important sub-concept of the pyramid is the value-enabling effects of the base factors. Good weather enables increased crop response to nitrogen, which enables an increased response from the specific crop variety and so on. Hence, nitrogen not only creates value by increasing yield, but enables additional value from other factors by ensuring they can fully express their respective contribution. High and consistent nitrogen use efficiency leads to more rational use and greater value. 2 Fertilizer FOCUS SEPTEMBER/OCTOBER 2015

3 feature Exploring the fertilizer value of efficiency In a perfect world, the amount of nitrogen fertilizer applied would be the optimum amount needed by the crop. In reality, the amount applied can be above or below the optimum and destroy value. Below optimum nitrogen leads to decreased yield and above optimum nitrogen leads to product wastage. Figure 2 is one possible nitrogen response curve which is an example and does not consider all permutations (that are beyond the scope of this article). (See figure 2). The calculated consequence of 20 kg N/ha below optimum reduces value to the farmer by USD99/ ha due to crop loss, but 20 kg N/ ha above optimum reduces value by USD18/ha due to estimated wasted fertilizer. By traditional thinking, the economic signal to the farmer is to over-apply nitrogen fertilizer because it provides better management of economic risk. Figure 1. Nitrogen is a major creator of value through increasing crop yield and enables the value of other factors by maximizing their contribution. Despite its pivotal role, nitrogen is one of the least innovative products among the leading crop production factors. Figure 2. A nitrogen response curve overlaid with impact of applying a nitrogen rate below or above the optimum. The value lost when expressed in $/ha (relevant to farmer), and the equivalency in $/mt of urea to indicate the value creation potential of more efficient, more accurate nitrogen fertilizer. Response curve based on data by Grove 3 A better option is to build in increased, consistent nitrogen efficiency with fertilizer technologies. Equating the value of missing the optimum at farm level back to the manufacturer level, the value in helping to hit the optimum is USD55 to USD303 on a per metric ton basis. The economic signal to the manufacturer is to maximize the fertilizer product efficiency and consistency so the optimum nitrogen can be matched. How the major fertilizer technologies work Understanding the lifecycle of nitrogen after fertilizer application is a daunting task. While in the soil, nitrogen is being transformed by chemical and biological reactions, taken up by the crop and lost through numerous pathways. By focusing attention on the key loss pathways we can find the main routes to value creation. To help visualize possible nitrogen loss mechanisms, think of the crop production system as a pipe (figure 3) where nitrogen as fertilizer is put in one end and nitrogen as a harvestable crop product is taken out the other end (see figure 3). The categories of the main technology-enhanced fertilizers relevant to extensive agriculture are shown in the lower section of figure 3. The two main categories are coated and stabilized fertilizers. Each category includes specific modes of action. A proper description of an enhanced product would be a nitrogen fertilizer is stabilized with the use of a urease inhibitor. Too often, the market mentally lumps together the different technologies although they perform distinctly different functions towards the mutual goal of improving efficiency. For clarity, technologically enhanced fertilizers are best described first by category and second by mode of action. For example, a nitrogen fertilizer stabilized (e.g. category) with a urease inhibitor (e.g. mode of action). The following generalizes the function of the technology categories and briefly summarizes the specific modes of action with a focus on nitrogen-based and ureabased fertilizers. Fertilizer FOCUS SEPTEMBER/OCTOBER

4 Figure 3: Analogy of the flow from nitrogen fertilizer to harvested crop through a pipe and the subsequent loss mechanisms of volatilization, denitrification and leaching. Below the illustration is one example to classify the technologies into categories and modes of action. The classification example is not exhaustive. In essence, coated fertilizers release incremental quantities of nitrogen over a longer period of time, which is theoretically more synchronized with the soil s capacity to retain the fertilizer and the crop s capacity to utilize the nitrogen. Stabilized fertilizers reduce formation of loss-prone nitrogen forms Nitrogen stabilizers reduce losses by maintaining nitrogen in forms such as ammonium (NH 4+ ), which is relatively stable against loss compared to the nitrogen gases (NH 3, N 2O, N 2) or the negativelycharged solute NO 3 -. Within the nitrogen stabilizers category there are two distinct technologies: urease inhibitors and nitrification inhibitors. Figure 4: Generalized schematic of a coated urea fertilizer and the gradual release of urea into the soil. The coating properties and amounts can be altered to achieve different rates of urea release from weeks to months. Not all coating materials are detailed in this generalized illustration. Urease inhibitors Urease is a catalytic enzyme that is richly abundant in soil (figure 4). The reaction is called urea hydrolysis while the loss mechanism is called ammonia volatilization. The hydrolysis reaction is a chemical reaction, not a biological-mediated reaction and therefore takes place in a much wider range of conditions than biological reactions, as described later. Coated fertilizers control the release of nitrogen into the system Using the pipe analogy, nitrogen losses can be reduced by reducing the pressure on the pipe and through the various loss mechanisms. A urea granule that has been coated with a membraneforming material (e.g. urethanes, elemental sulphur or other materials) will release the urea from inside the membrane to the surrounding soil (see figure 4) The release of fertilizer from the coated granule can be weeks or months longer than an uncoated granule. This technology is often best utilized in longer-season crops that need several months of nutrition or under very high leaching conditions where limiting the quantity released limits the risk of loss. Research programmes with coated fertilizer products are exploring the best fit in shortseason crops that receive multiple applications, a common tradition in European agriculture. To best utilize coated products in such markets, fertilizer practices may benefit from adaption to the function of coated fertilizers. Urease inhibitors stabilize nitrogen from loss by slowing the transformation of urea into ammonium. The molecular function of the inhibitor is to out-compete the urea molecule and join with the urease enzyme and thus reduce the rate of urea hydrolysis. The structural similarity between urea and the inhibitor enables the inhibitor to displace urea from urease but not be easily hydrolyzed itself - resulting in slower hydrolysis of urea. Further, the slower hydrolysis better maintains normal soil chemistry in a more stable condition favourable for retaining ammonium nitrogen in the soil (see figure 5). A crucial consequence of rapid urea hydrolysis is an intense ph increase 4 Fertilizer FOCUS SEPTEMBER/OCTOBER 2015

5 Figure 5: The two amides (-NH 2) within in urea are essentially two ammonium molecules that will be liberated by the urease enzyme. The proven urease inhibitors like the phosphoric triamde chemistry (listed in Table 1) mimic the structure of urea, but are not easily hydrolyzed to temporarily block urease and thus slow urea hydrolysis. of the fertilizer with inhibitors does not directly alter the nitrogen form or physical properties of the granule. Instead the fertilizer is a precise carrier to place the nitrification inhibitor in the same location and time as the fertilizer (see figure 7). directly adjacent to the point of application. The ph rise shifts the newly liberated ammonium (NH 4+ ) into an unstable ammonia gas (NH 3 ) which subsequently volatilizes into the air (see figure 6). It is sometimes misunderstood that urease inhibitors alter urea itself or coat the granule of urea. In reality, the urea-based fertilizers are simply a carrier for the inhibitor to the soil. The target of the inhibitor is the urease enzyme that accumulates in the soil as a free macromolecule independent of living organisms. Urease inhibitors must be delivered to the urease target at the same time as urea. The inhibitor slows hydrolysis and allows urea to diffuse into the soil rather than be instantly hydrolyzed and put at high risk of volatilization. The risk period for volatilization loss is short (typically, the first days after application) so the duration of urease inhibition coincides with this limited period when volatilization losses are possible. Stabilizing nitrogen with urease inhibitors reduces volatilization, which is the key inefficiency from urea-based fertilizers. Thus, urea fertilizers treated with a urease inhibitor can be used to upgrade performance or replace traditional non-volatile nitrogen fertilizers like nitrate-based products while providing other logistical and handling benefits. Nitrification inhibitors Nitrification inhibitors stabilize nitrogen by temporarily inhibiting the process of oxidizing ammonium by the ammonium mono-oxygenase enzyme (AMO) within soil bacteria. As discussed previously, the treatment The purpose of a nitrification inhibitor is to maintain the ammonium form and thus stabilize nitrogen from leaching below the root zone, which is associated with excessive levels of highly soil-mobile nitrate. Nitrate is a highly mobile molecule because its net negative charge decreases its retention capacity in a soil matrix that is also generally negatively charged. Nitrification inhibitors can substantially lengthen the period of the ammonium form and thereby extend the window of stabilization from loss as depicted in figure 8. Nitrification is a biological reaction that is mediated by living soil bacteria. As a biological reaction, the initiation and speed is linked to narrower environmental conditions than the chemical hydrolysis reaction catalyzed by urease. Nitrification is generally understood to be slow below 10 C because bacteria metabolism is slow. Some incorrectly assume urease activity and volatilization losses are equally temperature sensitive, but because hydrolysis is a purely chemical reaction, it is not bound by these biological constraints. In addition to stabilizing nitrogen from leaching losses, nitrification Figure 6: Visualizing how the chemistry of urea can be stabilized in soil with a urease inhibitor. With urea, the conversion to ammonium is fast which also increases the speed and extend of ph rise (left illustration). Treating urea with a urease inhibitor avoids the ph change by reducing the rate of urea transformation (middle illustration). Avoiding the high ph caused my urea transformation maintains the stable ammonium form (right illustration). Adapted from Christianson et al Fertilizer FOCUS SEPTEMBER/OCTOBER

6 Figure 7: Generalized schematic of oxidation of ammonium to nitrate by ammonium mono-oxygenate. Figure 8: Theoretical example of maintaining ammonium form for longer period and thus stabilize nitrogen from losses caused by leaching of excessive nitrate below the root zone. inhibitors reduce the denitrification and emission of nitrous oxide (N 2O) and N 2. Nitrous oxide losses are estimated at only one percent of applied nitrogen but, as a potent greenhouse gas, some stakeholders utilize nitrification inhibitors to reduce N 2O emissions. Emissions of N 2 are hard to measure and often ignored as a loss mechanism, but reduced N 2 emissions can be another benefit of stabilizing nitrogen with nitrification inhibitors. To date, stabilizing nitrogen with nitrification inhibitors is most commonly used in defined, highrisk leaching scenarios, or where the nitrification inhibitor is positioned to enable fewer applications of the nitrogen product. Figure 9: Performance of different nitrogen fertilizer strategies in U.S. maize production during a three-year trial. Adding 33 percent more urea (112 kg N instead of 84 kg N) was effective in matching the stabilized urea treatment in only one of three years. This trial indicated shortcomings of compensating losses with higher nitrogen rates compared to stabilizing nitrogen to prevent losses. The underlying data was provided by the University of Kentucky under a Research Trial Financial Support Agreement with Koch Agronomic Services, LLC and neither the University of Kentucky, nor the individual researchers referenced, endorse or recommend any product or service. Evidence of technological advances in nitrogen use efficiency Ammonia volatilization loss and its subsequent impact on crop performance are often easier to determine, correct and value than other loss mechanisms. Volatilization losses result in nitrogen drifting away from the field often within days of urea application and the negative results on crop performance can be substantial. Figure 9 compares maize yields with a moderate rate of nitrogen of 84 kg N/ha compared to a 33 percent increased nitrogen application rate of 112 kg N/ha to off-set volatilization losses and also compared to a moderate rate 84 kg N/ha treated with a urease inhibitor (trade name AGROTAIN nitrogen stabilizer). (See figure 9) In two of three years, the 33 percent increased nitrogen rate did not yield statistically higher than the moderate nitrogen rate. However, all three years, maize yield with urea + urease inhibitor was statistically superior to urea at equivalent rates and met or exceeded the yields with 33 percent higher nitrogen rate 4. This confirms the phenomena that attempting to compensate volatilization loss 6 Fertilizer FOCUS SEPTEMBER/OCTOBER 2015

7 Figure 10: Approximate volatilization loss of 45 percent of applied urea in winter-cold conditions and the high performance of a urease inhibitor (AGROTAIN stabilizer) to prevent nitrogen loss. This study also demonstrates volatilization loss occurs under a very wide range of conditions. The underlying data was provided by the Montana State University under a Research Trial Financial Support Agreement with Koch Agronomic Services, LLC and neither Montana State University, nor the individual researchers referenced, endorse or recommend any product or service. Figure 11: Volatilization losses when followed by immediate irrigation. Even as much as 12.7 mm of irrigation was not as effective as treating urea with a urease inhibitor (AGROTAIN stabilizer). Whether irrigation or less predictable rain events, the highest stabilization of nitrogen is likely achieved by treating with a urease inhibitor. The underlying data was provided by Oregon State University under a Research Trial Financial Support Agreement with Koch Agronomic Services, LLC and neither Oregon State University, nor the individual researchers referenced, endorse or recommend any product or service Near the border between Montana (U.S.) and Canada, urea is commonly applied to frozen soils because they support heavy fertilizer application equipment - with an assumed benefit of cold conditions minimizing volatilization loss. Dr. Rick Engel of Montana State University investigated the effectiveness of urea applied to frozen soil compared to urea treated with urease inhibitor (trade name AGROTAIN ). The results are summarized in figure 10. Over nine weeks of field measurements, the losses with urea were about 45 percent of applied nitrogen, four times greater than losses from urea treated with urease inhibitor. It was better to treat the source of the problem (urea) with a technological solution than attempt to manage the losses by timing the application during previously trusted early, cold conditions. Precipitation or irrigation following application of urea-based fertilizers is another traditional method of volatilization loss management. Researchers led by Dr. D. Horneck at Oregon State University (U.S.) examined the effectiveness of irrigation immediately following urea application. The data are shown in figure 11. Results indicate that the maximum irrigation rate used in the study, 12.7 mm of irrigation, was not as effective as a urease inhibitor in preventing volatilization losses. Even the ideal scenario of managing volatilization loss with immediate and substantial irrigation still resulted in nitrogen loss. Many urea users do not have access to irrigation and, if they gamble with the timing and amount of rainfall, they face an even higher risk. with high application rates may be unproductive because the urea itself actually drives the volatilization loss (figures 5 and 6) and adding higher urea rates may simply drive more loss. More efficiency is gained by stabilizing with a urease inhibitor rather than applying more urea. Traditional wisdom would indicate that urea fertilizer application can be timed with weather conditions believed to reduce volatilization losses. However, modern research following the advent of urease inhibitors has demonstrated superior approaches to retaining nitrogen. Two recent examples illustrate the potential inability of cold temperatures or immediate rainfall to arrest volatilization losses. Again, the evidence is compelling for treating urea with a highly effective fertilizer technology. Double stabilized nitrogen Under the right circumstances, nitrogen fertilizer is best stabilized by the use of both technologies; Fertilizer FOCUS SEPTEMBER/OCTOBER

8 feature Urease inhibitors to stabilize against volatilization losses, plus Nitrification inhibitors to stabilize against leaching and denitrification losses Figure 12: Appreciable nitrogen stabilization may come from a single technology like a urease inhibitor (AGROTAIN stabilizer) but an added benefit may be in combination with a nitrification inhibitor (SUPERU fertilizer). The double technology can stabilize nitrogen from all three loss mechanisms; volatilization, leaching and denitrification leading to greater yield beyond the benefit of a urease inhibitor. Examples of stabilization with both technologies in one fertilizer product are shown in figure 12 for urea and figure 13 for UAN. For most top-dress applications a urease inhibitor is a first choice as the risk of volatilization loss is inherent to urea and urea chemistry in soil. Not arresting the volatilization losses would seem to leave a large gap in the nitrogen stabilizer strategy where losses can occur first and fast from volatilization and slower and later from leaching and denitrification. Registration of technologies within the European Union legislation The European Commission, through its effort to create a single market throughout the European Union, has developed a fertilizer regulation that enables marketing in all Member States. The regulation EC 2003/2003 and amendments list urease and nitrification inhibitors that have been reviewed and registered under this legislative framework (table 1). The EC recognition of inhibitors provides some level of confidence that at least some efficacy testing is available. The continual challenge for these regulations is to foster innovation and adapt to technological progress. The recent registrations are an indicator that the regulation is adapting and enabling the broader use of the proven and trusted technologies. Summary of fertilizer technologies for stabilizing nitrogen Stabilizing nitrogen fertilizer from loss can substantially increase the value of the fertilizer product. The farmer is ensured maximum yield performance and/or less need to over-apply as an The underlying data was provided by Michigan State University under a Research Trial Financial Support Agreement with Koch Agronomic Services, LLC and neither Michigan State University, nor the individual researchers referenced, endorse or recommend any product or service. Figure 13: Maize yield performance from use of single (AGROTAIN stabilizer) and double inhibitor technologies (AGROTAIN Plus stabilizer) in UAN fertilizer, similar to the scenario in Figure 12. The underlying data was provided by the University of Illinois under a Research Trial Financial Support Agreement with Koch Agronomic Services, LLC and neither the University of Illinois, nor the individual researchers referenced, endorse or recommend any product or service. assumed safe-guard against fertilizer losses and inefficiencies. When the technologically-increased efficiency is calculated back to a fertilizer value, the stabilizer technology can add value of up to hundreds of dollars per ton of fertilizer and therefore a strong signal of economic opportunity to innovators in the industry. The two main categories in the market are coated and stabilized fertilizer products. Within the categories there are different modes of actions for example, within the stabilizer category there are urease inhibitors and nitrification inhibitors. Although the mutual goal is to increase efficiency, each technology works in a specific, understood and proven way. Some technologies are more situation-specific than others, so 8 Fertilizer FOCUS SEPTEMBER/OCTOBER 2015

9 Table 1: List of currently registered urease and nitrification inhibitors within fertilizer legislation EC 2003/2003. UREASE INHIBITORS Registration date Abbreviation Chemical name November 2008 NBPT N-(n-butyl) thiophosphoric triamide March NPT N-(2-nitrophenyl) phosphoric triamide November 2014* NBPT+NPPT(3:1) N-(n-butyl) thiophosphoric triamide + N-(n-propyl) thiophosphoric triamide Effective 01 Jan 2016 NITRIFICATION INHIBITORS Registration date Abbreviation Chemical name November 2008 DCD Dicyandiamide March 2012 DCD+TZ TZ+MP Dicyandiamide and 1,2,4-triazole 3-methylpyrazole and 1,2,4-triazole November 2014* DMPP 3,4-dimethyl-1H-pyrazole phosphate *Effective 01 Jan 2016 matching the technology function with the agronomic goal is vital to maximize results and value creation. The market can, and often does, confuse the technologies and their roles. However, awareness and clarity are improving as more industry participants utilize the technologies during manufacturing, distribution or use of the fertilizers. Further, the common-market regulation EC 2003/2003 provides baseline expectations for each type of recognized fertilizer technology and, hopefully, the regulation will adapt quickly to the rapidly growing role of fertilizer technologies in improving nitrogen efficiency. LEGENDS: 1. Trenkel, M.E Slow- and Controlled-Release and Stabilized Fertilizers: An Option for Enhancing Nutrient Efficiency in Agriculture. Second edition, IFA, Paris, France. 2. Below, F, The Seven Wonders of the Corn Yield World. cropphysiology.cropsci.illinois.edu/ research/seven_wonders.html 3. Grove Actual results may vary based on a number of factors, including environmental conditions. Yield benefits from application of stabilizer products to nitrogen fertilizer will only occur if nitrogen loss is a limiting factor. AGROTAIN, the AGROTAIN logo, SUPERU and the SUPERU logo are trademarks of Koch Agronomic Services, LLC in the United States and may be registered in other jurisdictions. Fertilizer FOCUS SEPTEMBER/OCTOBER