Duration: 10/01/2011 to 09/30/2016

Administrative Advisor(s):

NIFA Reps:

Non-Technical Summary

Statement of Issues and Justification

Issues: Designing efficient, economically sound and environmentally friendly corn (Zea mays L.) based cropping systems is a prerequisite to remaining competitive in today s global agricultural market place. The dilemma facing US corn producers and policy makers today is that the steady increase in corn yield over the past 50 years is partially attributed to the increasing use of N fertilizer, yet N fertilization comes with both a steep input cost and potentially high environmental cost. This is particularly true when more N is applied than the crop can effectively use, and adverse environmental consequences such as reduced ground and surface water quality, an increase in hypoxic zones off the mouth of our major rivers and increased emissions of powerful greenhouse gases (GHG) such as N2O can occur. Unfortunately, after nearly a century of research to develop precise N fertilizer recommendations and efficient N management systems, fertilizer N use efficiency (NUE) worldwide is still significantly less than 50%.

The relationship between corn yield and N uptake by the plant is strongly correlated. As yield potential increases the plant requires more N to produce the vegetation and grain associated with higher yield. However, while the relation between increasing corn yield and N uptake is tightly correlated, the relationship is not linear, and the relationship between yield and fertilizer N need is not nearly as well correlated. This is due in part to the varying capacity of soils to supply N to a crop each year. Particularly the rate at which N is mineralized from organic materials in the soil, and changes in potential N loss during the cropping season, a function of soil properties and crop management systems, as impacted by climate.

Though the individual processes which compose the N cycle in soils are well understood, less is known about how these processes, cropping systems, climate and N fertilization practices all interact to impact NUE. The interaction of sources of available N with soil organic matter and crop residue for example is rarely considered when making N fertilizer rate recommendations. However, N fertilization is known to lead to an increase in the mineralization of soil organic N, which can result in producers over-applying N fertilizer. But the same microbial processes responsible for mineralization can also result in immobilization or sequestering of N in soils, reducing NUE and crop yield in the year of application, and increasing mineralization, and potential N loss, at some latter time.

Rainfall and temperature are two important factors controlling most components of N cycling in soils. Thus a coordinated regional research effort which can look at gradients in temperature, precipitation and soil organic matter content across the Midwest, Mid-South and Great Plains and how these factors impact processes controlling both N mineralization and N losses from soils, is much more likely to arrive at a deeper understanding of N cycling and develop more efficient N management practices and increase NUE, than a series of independent, individual investigator projects conducted in a restricted geographical setting.

The long-term general goals of this regional project are to better understand how the interactions of soil, climate, cropping system and N fertilization practices impact NUE, and develop better N rate and management recommendations for growers. If these recommendations are utilized, growers will more efficiently utilize N fertilizers to meet the needs of increasing crop yield, while minimizing any potentially adverse effects on the environment. A key specific goal of this regional project is to use this new knowledge obtained to reduce the N fertilizer application to corn in the US over the next decade.

Justification: Corn production in the US today uses large amounts of N fertilizers due to the crops large N nutritional requirement. Soil N mineralization provides a substantial portion of corns total N need in most areas, and is supplemented as needed with inorganic fertilizer and organic manures and co-products. A key component to improved fertilizer N efficiency and reduced environmental impact is a better understanding and quantification of mineralized soil N release. Fertilizer N efficiency is normally calculated as (N uptake of fertilized plots-N uptake of unfertilized plots)/fertilizer N applied. An important, possibly incorrect, assumption in this approach is that release of organic soil N is unaffected by N fertilization. While it is commonly accepted that N fertilizer influences soil N mineralization by priming soil carbon (C) processes, little has been done to quantify these effects and incorporate this knowledge into our N management recommendations or calculations of fertilizer N use efficiency. Not accounting for N fertilizers impact on soil N release can lead to over-fertilization and increased N loss. Thus, quantifying uptake of fertilizer N by the crop and associated changes in soil N mineralization are paramount to developing sound management approaches that maintain high corn yields while minimizing N losses.

Though individual N cycle processes are well characterized, less is known about factors controlling Ns fate when these processes interact. The interaction of sources of available N with SOM pools is rarely considered when sufficient labile N is added as fertilizer. Most estimates of N mineralization are done in unfertilized conditions and lead to underestimates of mineralization and can lead to producers over-applying N fertilizer. This project plans to directly address the issue of N mineralization and how this impacts N fertilizer need and NUE in intensively managed systems.

Other processes leading to N loss can also impact NUE. Leaching, volatilization and denitrification are all important processes which are impacted by climate and soil water relations. A standard method used by many farmers to minimize the impact of these N loss mechanisms on yield, is add a little extra N as insurance. However, excessive N fertilizer use threatens environmental quality and human health. Soil nitrate moving to the Mississippi River and Gulf of Mexico is blamed for the increase in the hypoxic or dead zone noted off the mouth of the Mississippi River in summer. Emission of greenhouse gases, specifically N2O, through denitrification, is attributed to inefficient use of N fertilizers. Fertilizer N use also accounts for approximately 50% of the fossil energy input into intensively managed crops like corn. Thus environmental degradation and rising energy costs have become major impediments to both the profitability and sustainability of intensively managed corn systems in the US.

Climate change science suggests a slight increase in overall precipitation in the US Corn Belt, with a significant increase in intensity and frequency of large rainfall events in the spring/early summer corn growing season will result from continued climate change. This pattern is consistent with recently observed weather events. If these predicted changes in precipitation patterns were to continue, it would lead to increased loss of both mineralized and fertilizer N from soils, via denitrification and leaching. Loss directly from soils via denitrification, and in-stream denitrification of NO3- leached to surface waters, will increase emission of N2O. Therefore, one potential indirect consequence of climate change driven precipitation changes and N loss could be increased N-based greenhouse gas production.

Mitigation of the N flux from corn fields requires improved understanding of N release from soil organic N pools and the ability to adjust N rate recommendations from year to year to account for variation in N mineralization between years; improved N management practices to reduce fertilizer N loss and better synchronize soil and fertilizer N availability with corns N demand; and an increase in corn N use efficiency. Improved management practices include improved N rate recommendation systems that account for variations in N mineralization, and improved use of timing and placement of fertilizer N, selection of N source and additives that slow NO3- formation and/or ammonia volatilization, to reduce N loss and to better synchronize N supply with N demand. Improved N management practices may also include using crop sensors or other decision tools to guide in-season application, allowing a better prediction of N needs. All of these practices will aid corn producers in adapting to climate change, provide environmental benefits, improve corn yield, and give a better economic return to N.

The ultimate success of the project - reduced N loss, more efficient N fertilizer use and continued increase in corn yield - lies in the N recommendations and N management practices developed being adopted and utilized by corn growers across the corn producing regions of the U.S. This will require a thorough understanding of how these practices impact N availability and yield, understanding of the producer and adviser decision making process, and development of decision tools that will help people make good N fertilization decisions. Thus, a strong, extension education/outreach program targeted to producers and crop advisors (in addition to extension educators, local/state/federal regulatory personnel, and policy makers), is embedded in this project, since many of the current project team members have joint research and extension appointments.

The long-range prosperity of the U.S. agricultural and food system is increasingly tied to concerns over environmental impact including climate change. Unused N fertilizer represents a reduction in profitability, can cause environmental degradation and can impact global climate change. Over-application of fertilizer N is often the result of difficulty in predicting the amount of plant available N supplied from mineralization of soil organic N, or over estimating the potential for N loss. This project will provide information to more accurately determine the contribution of organic N to corns N needs, and resulting fertilizer requirement. In addition, decision making tools will assist growers in determining how best that fertilizer can be applied to result in high utilization by the target crop, and minimal loss to the environment. Improved N management across the U.S. Corn Belt will make important contributions to reduced N2O emissions, reduced NO3- movement to surface and groundwater, and will still result in high levels of corn productivity.

Related, Current and Previous Work

Nitrogen fertilizer use efficiency: Enhancing N fertilizer use efficiency in cropping systems is becoming much more important as the costs of fertilizers continue to increase and we become more aware of the consequences of reactive N escape into the environment, causing degradation in water quality, aquifer contamination and the release of N2O, a potent greenhouse gas, into the atmosphere. Groundwater nitrate (NO3-) levels have risen in many rural areas and are frequently found in violation of the USEPAs drinking water NO3- limit. Numerous studies have shown that degraded continental water quality has impacted the functioning of marine estuaries and near ocean areas through eutrophication. Anthropogenically driven increases in atmospheric N2O are beyond dispute and are significantly related to agricultural activities (IPCC, 2007). Nationally, agricultural soils are estimated to account for more than 70% of total U.S. N2O emissions, equivalent to 387 Tg CO2 annually.

In general, less than 70% (and as low as 20%) of applied N is taken up by crops (Meisinger and Randall, 1991). The un-used N is either stored in the soil, lost as NO3- by leaching to groundwater or runoff to surface waters, volatilized as ammonia or, after nitrification/denitrification, lost as NOx, N2O, or dinitrogen. Nitrogen leaving the agricultural system through denitrification is converted primarily to dinitrogen, but about is 1% lost as N2O (IPCC, 2007).

Much of the N applied to row crops is ammonium (NH4+) forming, and subsequently nitrified to the mobile anion, NO3-. Nitrate is readily available for crop uptake, or utilization by soil biota, but can also be lost to leaching and denitrification. In terms of crop uptake, utilization of conventional N fertilizers is often low. World wide, fertilizer N use by cereal crops is estimated to be only 33% (Raun and Johnson, 1999). However in the United States recovery values tend to be higher. In Kansas for example, an average recovery of 50% is used when making fertilizer recommendations.

N use efficiency values are also highly dependent on the method used to calculate them. The most commonly used procedure is the difference method (Varvel and Peterson, 1990) which compares the total plant nitrogen uptake from fertilized vs. unfertilized plots, and calculates a percent fertilizer N recovery. This procedure often produces higher N use efficiencies than using an isotopic N (15N) tracer due to the stimulation of mineralization of N from soil organic matter (SOM) by fertilizer N. Labeled N fertilizer is immobilized into SOM by the soil microbial population and additional unlabeled soil N is released and taken up by the target crop, resulting in a reduced fertilizer N recovery. Regardless of the method used however, the use of N by crops is not 100%, and residual N remaining in the soil, to be potentially lost to the environment, can be a costly consequence of crop production.

Making N Recommendations: Choosing the best N fertilizer rate is surprisingly difficult. Optimal N fertilizer rate varies widely from field to field (Lory and Scharf, 2003) and also from place to place within a field (Mamo et al., 2003; Scharf et al., 2005). There are a number of factors which must be considered when making the decision on N rate. The three most critical of which are: the amount of N which can be supplied by the soil; the amount of N which will be needed by the crop; and the impact of the soil, climate, cropping system and the selection of N source and application technology on the efficiency of N fertilizer recovery.

One of these key factors in developing N recommendations is estimating the amount of N which will be supplied by the soil. The addition of N fertilizer often invokes a priming response that enhances soil N mineralization (Kuyzayakov et al. 2000). Jansson (1958) demonstrated in laboratory incubations that considerable quantities of labeled N were immobilized during net mineralization of unlabeled soil N. The priming of soil N, or the added N interaction (ANI), has been demonstrated under a variety of field and laboratory conditions (Jenkinson et al. 1985; Hart et al. 1986; Powlson and Barraclough 1993). The implication of ANI is that the contribution of N from crop residue and SOM is often underestimated using unfertilized plots, due to the stimulation of mineralization with fertilizer N addition. The use of manure exacerbates the problem, creating a significant mineralizable, soil N supply for years, even decades, depending on manure rate, source, and history (Juma 1993). The role of the rotation effect , especially with legumes such as soybean and alfalfa, must also be considered (Elliott et al. 1987).

Complications in predicting the rates of soil N mineralization arise from inadequate understanding of the different rates of mineralization for individual SOM components (Parr and Papendick 1978). Microbial biomass pool size and activity are critical factors regulating turnover and stabilization of N in SOM. Since immobilization and mineralization are microbially mediated, these processes are highly controlled by climate, particularly temperature and moisture (Horwath 2007). Given this, the impact of residue management practices, climate gradients, soils, and soil properties such as drainage and pH, need to be clarified to develop a better understanding of the amounts of soil N which can become available and contribute to crop production each year. The amount of N being contributed form mineralization is critical to our ability to understand the amounts of fertilizer N needed by crops, and to develop highly efficient N fertilizer management systems.

Nutrient cycling models that predict N mineralization as a function of substrate (C and N) quality (i.e., C/N ratio) only partially describe soil N cycling. This predictive limitation impedes our ability to predict fertilizer N response. Mineralization of SOM and residue N is controlled by organic matter quality (Bosatta and Staaf 1982), clay interactions (Dashman and Stotzky 1986), inorganic N levels (Smith et al. 1989), and the lignin to N ratio (Melillo et al. 1982). Horwath and Elliott (1995) found that N is compartmentalized into labile residue, residue cell wall, microbial biomass, and microbial products during ryegrass decomposition. The compartmentalized residue N had various degrees of stability and was better defined by the concept of a combined C/N ratio rather than the total C/N ratio.

Decision tools, such as soil tests, are needed to help producers choose N rates more accurately. These tools need to be accurate and should operate on a fine scale to be most effective. At the very least they should be easily applied to all fields on a farm to diagnose variable N needs. Unfortunately, low accuracy has contributed to low adoption of prior decision tools (Kitchen and Goulding, 2001). The most widely-studied type of decision tool is soil testing. In the past century a tremendous number of different soil tests have been studied as regards to their ability to predict how much N will be available from the soil and consequently how much fertilizer will need to be applied. Although N need is sometimes accurately predicted across small areas in small datasets (Khan et al., 2001; Schmidt et al., 2009), the same tests have generally failed when applied across a larger area in large datasets. A recent example of that is the use of the Illinois amino sugar test (Khan et al, 2001) evaluated across the North Central region by this committee in the previous five year project cycle (Laboski et al., 2008; Scharf et al., 2006).

Residual mineral N tests have also been used in the region to estimate soil N supply for many years. Profile nitrate tests are routinely recommended for use in western Corn Belt states such as Kansas, Nebraska, North and South Dakota and the western portions of Minnesota. Recently these tests have also been examined in the colder Northern portions of the region such as Wisconsin, also. A recent survey conducted by the Kansas State University Soil Testing Lab of profile nitrate levels prior to corn planting showed a range of available nitrate N of < 10 to >300 kg N/ha, with an average of 101 kg N/ha (Mengel, unpublished). However, though profile N tests can be excellent tools in the drier portions of the country to assist in estimating available soil N, very few farmers take advantage of the tool. In the past decade less than 5% of the soil tests used to make fertilizer recommendations for corn in Kansas included a profile N test (unpublished data).

Tools based on measures of the growing crop are a recent development in predicting optimal N rate more accurately (Barker and Sawyer, 2010; Scharf and Lory, 2009; Ruiz Diaz et al., 2008; Hawkins et al., 2007; Scharf et al., 2006). Plant color and appearance can indicate areas where the soil is supplying a large amount of N, so that N fertilizer rate can be reduced and over-application avoided. Conversely, areas indicating N deficiency due to N loss or lower than expected N supply can receive higher N applications. Crop canopy sensors can help manage spatial variability in N need by indicating areas of adequate N vs. those requiring additional N to meet crop needs. These sensors can be coupled with rate controllers to provide on-the-go correction of N fertilizer rate during the fertilization process.

The amount of N needed by the crop: To make accurate N recommendations, one must also understand how much N is actually needed by the crop to achieve agronomic or economic optimum yields. A review of historic corn grain feeding values shows that the N content of corn grain has decreased dramatically over the past century. In the early portion of the 20th century corn grain routinely contained 11 to 12% protein. Today grain protein levels are routinely found <8%. Stanford (1971), in a review paper on the concept of N use efficiency in corn, showed a need for approximately 1.2% N in the total corn biomass, and found similar N contents of other cereal grains and forage grasses. Moll et al, 1982, demonstrated however that considerable genetic variability existed in corn in both the total amount of N present in the plant at maturity and the amount of grain produced per unit of N taken up. These authors went on to define two key components of NUE in crops: uptake efficiency or the amount of N taken up by the plant in relation to N supply; and utilization efficiency, or the amount of grain produced per unit of N taken up.
Most major corn seed companies are currently focusing efforts on developing new corn hybrids specifically for enhanced NUE. It is likely, based on the results of Moll et al and others that they will be successful in developing hybrids capable of more efficient recovery of soil and fertilizer N, and improved N utilization efficiencies. If so, this will likely require adjustments in our estimates of N needs when making N fertilizer recommendations.

Re-assessing the relative efficiency of available management tools: For the past 50 years, considerable applied research has been devoted to understanding the relative efficiency of different N sources, application methods and timings, and the use of products such as slow release fertilizers, and nitrification and urease inhibitors. In many states a large body of data exists defining conditions where these BMPs can be expected to provide improved NUE and in some cases enhanced profitability. However if predicted changes in rainfall distribution and intensity does occur, these relationships will need to be re-examined.

While some of these management tools and practices have clearly been shown to have advantage, farmers can be slow or reluctant to implement these practices for many reasons. Risk and timeliness are key factors which limit adaption in many cases. In many cases farmers continue to over apply N as insurance against N loss or under fertilization.

Producers potentially face new challenges in corn N management with climate change. Increased amounts and variability in spring rainfall are widely predicted for the U.S. Corn Belt (Karl et al., 2009). Both will affect corn production and make certain current N use practices less effective.

The largest effect of predicted climate change on N management and efficiency is the increased soil N loss potential in years with high spring precipitation. Excessively wet conditions often lead to yield limiting N deficiency, as appears to have happened across large swaths of the U.S. Corn Belt in 2008, 2009 and again in 2010 http://plantsci.missouri.edu/nutrientmanagement/nitrogen/loss.htm). Reexamining many of these management practices in light of higher N loss from mechanisms such as denitrification, leaching and ammonia volatilization could help producers adapt their N management choices, including N source and time of N application, to these climate changes. Incorporating this information into new decision tools could help producers choose their primary N management practices, adjust planned in-season N applications to fit current weather conditions, and decide when and how much rescue N to apply when primary N applications have been partially lost, as is occurring again with wet spring 2010 weather.

Summary: The component information needed to make good N management decisions is constantly changing. In addition, the costs to producers and society of over fertilization and inefficient N use are constantly increasing. A better understanding of the fundamental processes controlling the native soil N supply to crops and the loss mechanisms impacting soil and fertilizer N is needed.

Objectives

1. Develop a greater fundamental knowledge of the processes controlling soil N and C cycling, with particular attention to the role of factors such as soil, climate and cropping systems on the amounts of soil N supplied to crops and N loss from soils.
   
2. Reassess current N rate and management practice recommendations.
   
3. Develop user-friendly N management decision-making tools for use by growers.
   

Methods

The ability of this committee to conduct the research outlined below is contingent on their obtaining appropriate funding. The committee has in the past prepared and submitted proposals to a number of funding sources in pursuit of funds to support committee activities. It is the intent of the committee to actively pursue extramural funds needed to address each of these activities. Objective 1. Develop a greater fundamental knowledge of the processes controlling soil N and C cycling, with particular attention to the role of factors such as soil, climate and cropping systems on the amounts of soil N supplied to crops and N loss from soils. A multi-site field-scale study is proposed to assess soil characteristics that determine soil N availability. The study design addresses the temporal variability of soil N processes, influence of soil type and climate, and regional differences in corn production systems, such as crop rotation, tillage practices and N fertilizer management. Multiple sites creating transects for both temperature and precipitation across the region are planned. The individual experiments will utilize stable isotopic 15N to label the existing available soil N pool. After labeling, dilution of the added isotopic N is used to determine the amount of soil N that becomes available during a growing season. The crop is used to assess available soil N via determination of N uptake. Quantification of soil C and N processes, including N mineralization and gaseous emissions resulting from denitrification where appropriate, will be done using 15N pool dilution, standard gas flux measurements, and harvest indices. The research concept proposed, is to determine what has traditionally been called the A-value , or the size of the available soil N pool as compared to the availability of an added labeled N source (Fried and Dean, 1955). Much A-value research has been carried out with N but the concept holds for other soil nutrients as well. Soil processes that have an effect on available soil N will be reflected in the A-value. The N A-value for a soil is an indirect reflection of total soil microbial activity and the mineralizability of soil N. An increase in the soil N A-value is strongly and positively related to the rate of N-uptake (Broadbent, 1970). The N A-value, in essence, is a parameter that can be used as an indicator of soil N quality, and the ability of a soil to supply N. The soil N A-value is an ideal method to measure differences in soil N quality brought about by changes in management practices or past fertilizer N use (Stevenson et al., 1997). Specific methods to be employed: a. 15N soil labeling studies Micro-plots will be established at each site where enriched stable isotope 15N will be applied. The experiment will be replicated and configured in a randomized design, with six N rates, at least one rate which is beyond the normal N response range, to provide a full grain yield N response curve . The micro-plots will be implemented within multiple fertilizer rates at each site. Each micro-plot will receive a rate of 15N equivalent to 5 kg N per ha at 10 atom% 15N excess. The 15N will be added prior to planting, ideally within 1 to 3 days of planting, and mimic actual fertilizer application. However, since soil management may differ among states and regions, application may be made at sidedressing. The labeled fertilizer will be placed below the soil surface to maximize utilization by the crop and minimize immobilization in any surface residue. Soil inorganic N will be determined at the time of 15N application. Extractable ammonium and NO3- will be measured both prior to planting and at the end of the growing season from composite soil cores taken at 0 to15, 15 to 30, 30 to 60, 60 to 100, 100 to 150 and 150 to 200 cm in depths. Total N and organic C will be determined in soil and plant samples, with plant sampling at corn maturity to include all above-ground plant parts including grain. Analysis will include 15N content. In order to understand how soil organic N priming affects crop N uptake and other sources of crop N, the total crop recovery of 15N applied as fertilizer-N will be determined as %N derived from fertilizer (Devêvre and Horwath, 2001). Soil cores will be analyzed immediately following sampling for exchangeable NH4+ and NO3- using the KCl extraction method described by Brooks et al. (1989). A soil sub-sample will be analyzed for total organic C and N and atom %15N. Soils will be dried and analyzed for total N and 15N content as described above. Plant tissue samples will be analyzed for atom %15N using continuous-isotope ratio mass spectrometry at the Stable Isotope Facility, University of California Davis. To determine total plant N for each treatment, several whole plants will be harvested from each microplot and analyzed for total N and 15N. The amount of N in each N rate treatment derived from 15N-labelled source can be determined. The contrast between the 15N labeled crop and 15N labeled fertilizer will be used to determine soil N uptake and the extent of soil organic N priming. The N use efficiency (NUE) of the added N for each field treatment will be determined according to Eagle et al. (2000). By determining the amount of 15N and fertilizer15N taken up by the crop the mass balance approach can be applied to determine the amount of N not accounted for in the crop or soil, such N loss assumed due to denitrification, volatilization, leaching, or error in estimating soil N. b. Gaseous N flux measurements We will measure Gaseous N flux (N2, NO and N2O) intensively when the potential for emissions is high, but less frequently when emissions are expected to be low. Episodes of high emissions occur when both soil NO3- concentrations and water-filled pore space (WFPS) are high, for example during irrigation or rainfall events soon following N fertilization (Bronson and Mosier, 1993; Burger et al., 2005; Dobbie et al., 1999; Simojoki and Jaakkola, 2000), and the incorporation of residue, especially followed by soil wetting (Baggs et al., 2003; Burger et al., 2005; Kaiser et al., 1998; Velthof et al., 2002). Gas flux will be measured using a static chamber technique (Hutchinson and Livingston, 1993). The gas emissions will be measured starting immediately after fertilization using the chamber-based trace gas flux measurement techniques, sampling frequency, and laboratory analysis protocol outlined by the USDA-ARS GRACEnet (Greenhouse gas Reduction through Agricultural Carbon Enhancement network) (http://www.ars.usda.gov/SP2UserFiles/person/31831/2003GRACEnetTraceGasProtocol.pdf ). Air samples will be collected from the headspace of the chamber at 0, 30 and 60 min after chamber deployment, and samples will be analyzed by a Shimadzu gas chromatograph (Model GC-2014) linked to a Shimadzu auto sampler (Model AOC-5000) at University of California-Davis. c. Economic N Grain and biomass yield and crop N uptake will be assessed using hand harvest of each plot. A sub-sample of the biomass will be dried, ground to a fine powder, and analyzed by a Costech C and N analyzer via combustion. The minimum amount of fertilizer N needed to achieve maximum yield, or economic optimum N rate, will be determined from the N rate and grain yield data. The economically optimum N rate and gaseous flux data can also be used to evaluate the hypothesis that N2O emissions increase non-linearly at N fertilizer levels exceeding the economically optimum N rate. Potential N2O offsets through improved fertilizer N management without yield penalty will be calculated and demonstrated. Objective 2. Reassess current N rate and management practice recommendations. A considerable body of work has been done over the past 40 years evaluating N fertilization practices such as rate, timing, placement, fertilizer N materials and additives to slow the conversion of ammonium N to nitrate, reduce N loss and better synchronize N supply and N demand. However changes in plant genetics, cropping systems, and tillage practices raises questions as to the applicability of this past work today. Predicted changes in rainfall quantity and intensity across the region also raises additional questions as to the applicability of current recommendations. This work will be evaluated at multiple sites across the corn production region. This work will provide a reassessment of current N rate and application/management practice recommendations for corn producers that allow choices in response to different soil and climatic conditions. Producers can better adapt their crop production systems to climate change, providing more stable economic and environmental outcomes. Each trial will follow a common protocol, addressing experimental design, number of replications, plant and soil sampling, corn canopy N sensing, corn N uptake, and calculated N use efficiencies. There will be a minimum set of parameters measured, with sites having the freedom to do additional sampling/measurement if desired. Specific Methods to be employed: A core set of N management treatments will be implemented at all trials across the region. These treatments will encompass several N management systems and will be a set combination of N fertilizer products (including controlled release and coated fertilizers), application times, and inhibitors to control ammonia volatilization and nitrification. Additional N management treatments, appropriate to local needs, will be implemented by the local scientist at each site. These could include additional fertilizer sources, application times or methods, as well as new or experimental inhibitors or controled release products. Core treatment set. The following 12 core treatments will be included at all locations: 1. True No N control; 2-6. N rate response, Spring preplant UAN solutions, injected at rates of 45, 90, 135, 180, 225 kg N/ha; 7. 90 kg N/ha as UAN solution sidedressed, injected below the soil surface; 8. 90 kg N/ha as UAN solution with nitrapyrin nitrification inhibitor spring preplant injected; 9. 90 kg N/ha as UAN solution broadcast in the spring prior to planting and not incorporated; 10. 90 kg N/ha as Urea broadcast and not incorporated prior to planting in the spring; 11. 90 kg N/ha as Urea+Agrotain broadcast and not incorporated in the spring prior to planting; and 12. 90 kg N/ha as a 80% ESN coated urea/20% Urea blend, broadcast in the spring and not incorporated. If a trial site has other important N products/timings or N management systems that should be studied for a particular geographic area, then those can be added as additional treatments. For example, since 50% of the fertilizer N consumed in Iowa and Illinois is anhydrous ammonia (and equipment is available to apply it to trial plots), then fall and spring pre-plant (and perhaps sidedress) anhydrous ammonia could be included. Core Measurements The following parameters will be measured at each trial site: 1. Routine soils tests and profile N levels to 1m. One sample per replicate before treatment application to provide site characteristics and understanding of any potential additional nutrient requirements. 2. PSNT, zero N rate plots only. To provide an indication of the trial site N responsiveness. 3. Canopy sensor NDVI measurements for all plots, to provide measures of plant N response, treatment effect, and for specific study sites evaluation of crop canopy sensing based N rate determination. 4. Aboveground plant biomass and N uptake for all plots at plant maturity (vegetative, cob, grain separate), to measure crop N response, total plant N uptake, and NUE determination. 5. Grain yield, to measure N rate response, determination of maximum and economic optimum N rate, and evaluation of set treatment effects. Objective 3: Develop user-friendly N management decision-making tools. Traditionally, the emphasis has been on the use of soil testing as a tool to estimate the amount of N being supplied by the soil when making N recommendations. However, since a major component of soil supplied N is mineralized N, the product of a microbial process impacted greatly by water and temperature, soil testing has proven to be a less than satisfactory decision making tool. Currently, considerable interest exists in the use of crop sensors to let the crop N status at specific growth stages define N need. This can be useful in fine-tuning N applications based on variability in soil N supply and assessing the impact of N loss. Groups within this committee are interested in both uses. Using sensors to guide late season N applications to compensate for N loss. A spring precipitation gradient will be identified in June based on radar-derived precipitation maps. Corn yield response experiments will be conducted in producer corn fields along this gradient where high levels of precipitation would be expected to result in above normal levels of N loss. Experiments will be conducted using traditional small plot techniques with hand application of fertilizer and hand held sensing equipment to monitor plant reflectance, or as strip tests using field scale equipment. Relationships between plant reflectance and response to late season N will be established. Other potential tools such as SPAD meters, color charts and green leaf counts will also be used to establish similar relationships with late season N response. Once these relationships have been established and preliminary algorithms have been developed, on-farm tests and demonstrations of these preliminary decision-making tools will be conducted in replicated field-length strips comparing the producer s standard decision to a decision-tool-aided system. This will help with both refinement of the decision tools and making key innovators and early adoptors aware of the value of the tools. Once basic response relationships between reflectance measures and yield response are established, these relationships can be integrated with precipitation data from regional climate centers to produce web-based maps of potential yield response. Statistical analysis, discussion, the results from Objective 1 and 2 experiments, the literature and expert knowledge will be used to develop these regional N risk assessment tools. Using sensors to guide late season N application to compensate for less than expected N mineralization. Tools to assess risk of N loss from various N forms and application times under above normal rainfall events are one likely outcome. An additional way sensor technology could lead to increased NUE is reducing normal preplant or early sidedress N application rates, and making a final adjustment application if needed to compensate for lower than normal mineralization or residual inorganic N supply. The first step would be synthesis of past and present work by group members to determine the suitability of crop reflectance sensors as a tool for guiding N application rate. On-farm research and demonstrations experiments utilizing a number of the currently available crop sensing tools would be conducted to determine the accutracy and feasibility of these decision-making tools to make late season (late vegetative to early reproductive growth stages) N recommendations for corn. Analyze results of present and past experiments to see whether management and weather history can be used to predict the scale of N mineralization from soil organic matter in the current year. If so, develop a decision tool(s) that will enable producers to identify whether this year s mineralization is likely to be average, below-average, or above-average. They can then adjust their N rates accordingly. One possible tool would be a web-based map identifying regions of the U.S. (or at least the Corn Belt) that are expected to have average, below-average, or above-average N mineralization this year.

Measurement of Progress and Results

Outputs

• Data will be collected to further our understanding of the "priming effect" in soils.
• An assessment of current N fertilizer recommendations and practices
• New sensor based decision making tool to guide N fertilization decisions.
• Publications on N cycling, N fertilization and N management
• Webinars aimed at enhancing the understanding of CCA's on N management

Outcomes or Projected Impacts

• A better understanding of N and C cycling in soils, particularly the role of N fertilization on N mineralization, the "priming effect."
• Producers, CCA's and farm advisers will have a better understanding of N cycling in soils and impacts on N fertilizer use efficiency
• N fertilizer rate and practice recommendations will be improved
• New sensor based decision making tools to guide N fertilization decisions will be developed.
• N fertilizer use will be reduced while yields will be maintained or increased

Milestones

(1):methods publication describing many of the ways which are commonly used to measure or define nitrogen use efficiency and its component parts, Nitrogen Uptake Efficiency and Nitrogen Utilization efficiency.

(1):oposals will be submitted to appropriate funding agencies to obtain funding for Objectives 1, 2 and 3.

(2):series of Webinars will be developed aimed towards CCA's on N and C cycling in soils and efficient nitrogen fertilizer management.

(2):eld work will be implemented on Objectives 2 and 3.

(3):print/web based publication will be developed on global and soil N cycling tying together how soil N processes and field N management decisions effect global environmental issues.

Projected Participation

View Appendix E: Participation

Outreach Plan

As stated previously, the ultimate success of the project - reduced N loss, more efficient N fertilizer use and continued increase in corn yield - lies in the N recommendations and N management practices developed being adopted and utilized by corn growers across the corn producing regions of the U.S. This will require a thorough understanding of how these practices impact N availability and yield, understanding of the producer and their advisers decision making processes, and development of decision tools that will help people make good N fertilization decisions. Thus, a strong, extension education/outreach program targeted to producers and crop advisors (in addition to extension educators, local/state/federal regulatory personnel, and policy makers), is required.

Several of the project team members (Fernández, Laboski, Mengel, Mullen, Sawyer, Lamb and Scharf) have extension appointments. As such, the knowledge gained in this research along with decision-making tools that are developed will be extended to corn producers, crop advisors, extension educators, regulatory personnel, and policy makers, through team members individual on-going extension programs. These on-going extension programs include newsletter articles, county/regional extension meetings, and statewide crop advisor/ag retailer conferences and producer meeting series (eg. Wisconsin Crop Management Conference, Iowa Integrated Crop Management Conference, Indiana/Ohio CCA Conference, Illinois Ag Masters and Corn and Soybean Classic conferences, Iowa Crop Advantage Series, etc). Annually, these state crop management conferences draw audiences totaling 8,000-12,000 people; many who directly influence corn producers N rate and management decisions.
Print/web based publications have been the past standard for extension education materials. It is expected that our audience will still find these types of educational materials valuable in that detailed, written publications are good reference materials. Thus, initial planning for a written publication on global and soil N cycling, tying together how soil N processes and field level N management decisions affect global environmental issues. The audience for this publication will be people with a need for a broad basic understanding of the issues. It is expected that this publication will be developed during the first/second year and will be published sometime in the third/fourth year of this project cycle. The publication will be published as a PDF for free internet download.
As research projects being proposed in Objectives 1, 2 and 3 are completed additional publications will be developed specific to individual states or multi-state regions and highlight the soil N processes, N management research results, and appropriate decision-making tools developed in this project, and collectively will serve as a guidebook to how corn N application rates can be reduced. These state/regional publications will also be published as a downloadable PDF, similar to the national publication.
We will develop a national webinar series with the collective title: Improving environmental and economic sustainability of corn production through improved N management. This series of four to six webinars will discuss basic and advanced information on: soil N mineralization; corn N needs; environmental problems associated with N; and delivery of N management tools (some developed in this proposed project) that can be used to help refine N rate and/or management in the face of problematic climatic situations. These webinars will feature different project team members as presenters and will be available to a national audience. Webinars will be advertised through state Extension newsletters, state Certified Crop Advisor programs and the eXtension website. Polls will be used at the beginning and end of each webinar as a pre-test/post-test means to evaluate relevancy and usefulness of the information delivered, along with the amount of knowledge participants gained. Webinars will be recorded and the video will be post processed to allow viewing from a website. Internet posted videos will allow greater access to the educational material and extend the useful life of the webinar series. We will work with the American Society of Agronomy Certified Crop Advisor Program to provide continuing education units (CEUs) for webinar attendees and develop a means for those that later view a video of the webinar to obtain CEUs. Cross promotion of other project educational materials and events will occur at the end of each webinar. We will also propose that a self-directed CEU be made available through the American Society of Agronomys publication Crops and Soils. This is a national circular that is made available to all current CCAs.

Organization/Governance

The voting membership of the NC 1032 Regional Committee will consist of the official representative(s) from each participating AES or cooperating agency group. The Administrative Adviser and NIFA/CSREES Consultant will serve as non-voting, ex-officio members of the committee. The participation of additional interested people from member AES and agencies is encouraged. Membership in the Committee is not limited to states within the North Central Region.

The Executive Committee of the committee will consist of a Chairperson, Secretary, and Member-at-Large. Members of the Executive Committee must be official members of the regional committee. Each year the regional committee will elect a new Member-at-Large for a three year leadership term. In year two the Member-at-Large will automatically move up to Secretary, and in year three will become Chair. At the discretion of the Chair, the Administrative Advisor and other additional members can be designated as ex-officio members of the Executive Committee.

The Chairperson sets the agenda and presides at the annual meeting, and any other meetings as deemed necessary. The current chair is responsible for preparing the annual report and seeing it is posted on the NCRA website. In addition, the current chair is responsible for preparation of any documents required for the mid-term review, preparation and up-loading of the five year project proposal, and appointing working committees as needed.

The secretary will keep the official minutes of all meetings of the regional committee and see that they are up-loaded to the official NCRA project website in a timely manner. They will preside over any meetings the chair is unable to attend and will become chair of the regional committee in the event that the elected committee chair is for any reason unable to continue in this capacity.

The Member-at-Large is responsible for all local arrangements for meetings of the committee. They will also assume the duties of the secretary in the event they are unable to attend a meeting, or are required to assume the responsibilities of the chair.

The Executive Committee will review and make recommendations concerning the conduct of business by the regional committee. The Committee will have a regularly scheduled annual meeting. In addition, the Chair may call other meetings of the Committee and the Administrative Adviser as deemed necessary.

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Attachments

Land Grant Participating States/Institutions

CA, GA, IA, KS, KY, MD, MI, MN, MO, MS, NE, OH, UT, WI

Non Land Grant Participating States/Institutions