Adapt-N Recommendations Reduce Environmental Losses

Lindsay Fennell1, Shai Sela1, Aaron Ristow1, Bianca Moebius-Clune1, Dan Moebius-Clune1, Bob Schindelbeck1, Harold van Es1, Shannon Gomes2
1Soil and Crop Sciences Section, School of Integrative Plant Science, Cornell University; 2Cedar Basin Crop Consulting

Soil nitrogen is spatially and temporally variable and it can be challenging for farmers to determine a location-specific optimum N rate, often leading to excess (insurance) applications. Corn N management is therefore relatively inefficient, with N recovery (the proportion of applied N taken up by the crop) often being less than 50%. The nitrogen that is lost through leaching and runoff has a massive negative effect on groundwater aquifers and aquatic biota in streams and estuaries downstream. The Chesapeake Bay and Gulf of Mexico are notable concerns and ambitious nutrient reduction goals have been established. Another major concern is the gaseous nitrogen loss that can result in high emissions of nitrous oxide (N2O), a potent greenhouse gas for which agriculture is the main anthropogenic source.

These increased N fluxes into the environment have significant economic and environmental costs. There are a number of approaches to reduce such N losses, including reduced N applications, cover cropping, buffer strips, etc. Arguably the most important one is the better estimation of the optimum N rate so that excess N applications can be avoided.

Adapt-N and Strip Trials

The optimum N rate depends on numerous factors including the timing and amounts of early season precipitation, previous organic and inorganic N applications, soil organic matter, carry-over N from previous cropping seasons, soil texture, rotations, etc. Adapt-N is a simulation tool that combines such location-specific soil, crop and management information with date-specific weather data to estimate optimum N application rates for corn. It thereby allows for precision N management specific to each production environment (field, season, management). The tool was developed at Cornell University and has been licensed for commercial use (adapt-N.com).

The Adapt-N tool also has environmental utility as it simulates leaching losses from the bottom of the root zone and gaseous losses into the atmosphere due to denitrification and ammonia volatilization. Both leaching and gaseous losses are simulated based on soil water dynamics and the use of N loss equations that are modified by temperature and water conditions.

The Adapt-N tool was used in 115 paired field strip trials with two to seven replications conducted mostly on commercial farms (two university research farms were involved) in New York and Iowa during the 2011 through 2014 growing seasons (Fig. 1). Trials were distributed across both states under a wide range of weather conditions, and involved grain and silage corn, with and without manure application, and rotations of corn after corn and corn after soybean. The pre-plant or starter fertilizer rates averaged 76 and 56 lbs/ac for the NY and IA trials, respectively. In each trial, the treatments were defined by the amount of N applied at sidedress, where the rates were:

(i)     the Adapt-N recommendation for the date of sidedress, and

(ii)    a Grower-selected rate, which typically represented their conventional practice.

We determined corn yields and associated profit differences for the two treatments. In order to directly compare the environmental fluxes resulting from Adapt-N and Grower sidedress N applications, we ran full season simulations (up to December 31st) for all 115 trials and estimated the environmental fluxes that occurred after the application of sidedress N.

Vanes Figure 1 - AdaptN Recommendations

Results

Complete results for this study are presented in Sela et al. (in review). We measured clear agronomic benefits from the precision approach of the Adapt-N tool over the Grower treatment: N rates were on average reduced by 40 lbs/ac (34%), while average yields were actually 2 bu/ac higher. This resulted in $26/ac higher profits on average over all 115 strip trials.

For all trials in both states, simulated total N losses (leaching and gaseous combined) were on average reduced by 24.9 lbs/ac (38%) for the Adapt-N recommended rates compared to the Grower-selected rates (Fig 2), in line with the lower applied N rates. Simulated total N losses for the Iowa trials were on average somewhat lower than for the New York trials, presumably due to different climate and soil conditions.

Vanes Figure 2 - AdaptN RecommendationsLeaching losses: The average simulated leaching losses of 35.3 and 22.6 lbs/ac (Figs. 2a and 3a) for the Grower and Adapt-N treatments, respectively, are comparable to measured leaching losses from other experiments in the literature. Adapt-N rates resulted in an average reduction of 19.6 lbs/ac (39%) in New York and .3 lbs/ac (3%) in Iowa in simulated leaching losses compared to the Grower rates, and reductions were consistently higher for the New York trials. This can be attributed to several characteristics of the New York sites, including (i) generally wetter climate with much pre- and post-season precipitation, (ii) lower denitrification losses relative to leaching due to generally coarser soil textures, and (iii) shallower rooting depths causing less water and N uptake in the lower soil profile. Simulations were terminated on December 31 of each year, so are underestimates of actual benefits in both states, as further N leaching may still have occurred during spring and winter prior to the next growing season.

Vanes Figure 3 - AdaptN RecommendationsGaseous losses: Simulated gaseous losses (Figs. 2b and 3b) were also lower for the Adapt-N compared to the Grower treatment (average reduction of 12.9 lbs/ac; 39%). The 2011 and 2012 seasons for the New York trials resulted in >50% reductions in simulated gaseous losses when using Adapt-N vs. Grower rates. Again, benefits were generally greater in New York than Iowa, although the relative reduction in gaseous losses in Iowa were greater (18%) than the reduction in leaching losses (3%).

Conclusions

The results of this study show environmental gains from using Adapt-N’s precision management approach to estimating in-season N rates across a robust number of fields, soil types and weather conditions in Iowa and New York. In all, the Adapt-N recommended N rates adapted effectively to the varying field and weather conditions, were generally lower than the Grower’s regular N rate, and achieved both economic and environmental benefits. Although the benefits varied by year, state and site, the overall environmental losses were reduced by 24.9 lbs/ac (more in NY than IA) through the use of this precision management approach. This implies a reduction of 38% in the post-application N losses. In all, use of Adapt-N can significantly contribute to nitrogen reduction goals. A final note: The potential benefits of its use are likely underestimated in this study, especially for IA, as the participants already represented a progressive group of growers who optimize their own N timing and placement decisions with sidedress applications, while many Midwestern growers still apply most of their nitrogen in the fall or at planting.

Acknowledgements

This work was supported by funding from the USDA-NRCS Conservation Innovation Program grant number 69-3A75-10-157, New York Farm Viability Institute, USDA-NIFA WQ grant number 2013-51130-21490, the Northern New York Agricultural Development Program, USDA-Sustainable Agriculture Research and Extension grant number LNE13-328, the International Plant Nutrition Institute, and the McKnight Foundation. We are grateful for the cooperation in field activities from Keith Severson, Sandra Menasha, Anita Deming, and Michael Davis of Cornell Cooperative Extension, David DeGolyer, Dave Shearing and Jason Post of Western NY Crop Management Association, Eric Bever and Mike Contessa at Champlain Valley Agronomics, Eric Young at the Miner Institute, Peg Cook of Cook’s Consulting, and Hal Tucker, Michael McNeil, and Frank Moore of MGT Envirotec. We also are thankful for the cooperation of the many farmers who implemented these trials on their farms.

References

Sogbedji, J.M., H.M. van Es, J.J. Melkonian, and R.R. Schindelbeck. 2006. Evaluation of the PNM Model for Simulating Drain Flow Nitrate-N Concentration Under Manure-Fertilized Maize. Plant Soil 282(1-2): 343–360

S. Sela., H.M. van Es, B.N. Moebius-Clune, R. Marjerison, J.J. Melkonian, D. Moebius-Clune, R. Schindelbeck, and S. Gomes, Adapt-N Recommendations for Maize Nitrogen Management Increase Grower Profits and Reduce Environmental Losses on Northeast and Midwest USA Farms, Submitted to the Soil Science Society of America Journal

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What’s Cropping Up? Volume 25, Number 4 – September/October

What’s Cropping Up? Vol. 24, No. 5 – September/October – Full Version

Implementation of a Soil Health Management Plan Resolves Pond Eutrophication at Tuckaway Farm, NH

Bianca Moebius-Clune, Dan Moebius-Clune, Robert Schindelbeck, Harold van Es – Section of Soil and Crop Sciences, Cornell University; Dorn Cox – GreenStart; Brandon Smith – NH NRCS

Dorn Cox manages Tuckaway Farm, his family’s 250 acre multi-generational diversified organic operation in Lee, NH. He is also a PhD Candidate at the University of New Hampshire, and director of GreenStart, an educational non-profit organization set up to foster a resilient food and energy system in New Hampshire by providing technical education and practical agricultural examples.  Dorn discovered that the Cornell Soil Health Test was available in 2009, while discussing soil testing with Brandon Smith, State Agronomist of the NH NRCS. “It was a good fit for GreenStart’s mission and I was excited, because the test not only incorporated biological, physical, and chemical indicators, but it also presented an approach for land management planning and adaptive management.“  In the spring of 2010 he submitted his first samples.

A collaborative project was initiated among partners at NH NRCS, Cornell, Greenstart, NH Conservation Districts, and NH farms in four counties. The goal was to develop a framework for a soil health test-informed Soil Health Management Plan (SHMP), analogous with the NRCS’s Nutrient Management Plan, but with biological and physical test results to be considered, in addition to standard soil test results. Additionally the project set out to build local equipment infrastructure to enable soil health management through education and equipment rentals, and to demonstrate implementing these plans.

Tuckaway Farm became the first test case for the new planning and implementation framework. Through the particular resource concerns identified, this case became strong evidence for the need to move beyond Nutrient Management Planning, to Soil Health Management Planning. Implementation of a targeted set of soil health management practices has now resolved eutrophication problems that had made the farm irrigation pond unusable for recreation since 2009.

Background: from Soil Health Testing to Planning to Implementation

Soil health constraints beyond nutrient deficiencies and excesses currently limit agroecosystem sustainability, resilience to drought and extreme rainfall, and progress in soil and water conservation. The Cornell Soil Health Assessment (http://soilhealth.cals.cornell.edu/), makes it possible to identify and explicitly manage constraints. Available to the public on a fee-for-service basis since 2006, it provides field-specific information on constraints in biological and physical processes, in addition to standard nutrient analysis.

A more complete understanding of soil health status can better guide farmers’ soil management decisions. However, so far, there had been no formalized decision making process for implementing a soil health management system that alleviates field-specific constraints identified through standard measurements and then maintains improved soil health. We created a framework for developing Soil Health Management Plans (SHMP) for a farm operation, including:

  1. A detailed listing of management suggestions specific to each indicator showing constrained soil functioning, and relevant NRCS cost-shared practices that could be applied to address the resource concerns identified through a soil health assessment.
  2. A new Cornell Soil Health Assessment report format that more explicitly provides initial interpretation, prioritization, and management suggestions, from which a SHMP can then be developed.
  3. Six general steps for the planning and implementation process (Figure 1).
  4. A pilot SHMP template for such plans that includes purpose, site information, assessment results and interpretation, and planned practices via a multi-year management calendar outlining a specific plan for each field.

We developed a pilot multi-field SHMP using this framework at Tuckaway Farm, owned and operated by the Cox family for over 30 years, and at 17 additional NH operations. The purpose of this case study is to share the outcomes achieved in one of Tuckaway Farm’s fields, and suggests, based on this example, that a broader soil health assessment-based planning approach is necessary to maintain our nation’s most vital resource: our soil.

Figure 1. Soil Health Management Planning Process Overview
Screen Shot 2014-09-16 at 11.46.28 AM

Planning, implementation and evaluation for a field at Tuckaway Farm in 6 steps

1. Farm background and management history

Dorn and his father Chuck tell the story of a 30 year evolving family endeavor. Much of the land has been in long-term continuous organic hay for off-farm sales, with limited use of inputs such as wood ash and horse manure. The farm has added vegetable rotations and fruit over the years, and more recently dairy, eggs, meat, grains, and oils, among other products, all with organic certification. A Comprehensive Nutrient Management Plan determined that net nutrient exports off the farm were causing nutrient deficiencies in many long-term hay fields. The land base can potentially sustain a much larger number of animals. Management change has sped up since about 2009, with additional products being developed, experimentation with reduced tillage, cover crops, and rotational grazing, and a decrease in hay export as the younger generation farmers are building animal-based enterprises. Diverse equipment, owned by the farm, Greenstart, and the county conservation district, is available.

The Pond Field, the subject of this case study, is a long-term hay field, occasionally grazed outside of the CNMP-required buffer strip around the pond’s perimeter. The field’s soil is an inherently well-drained but easily eroded Hollis-Gloucester fine sandy loam of mostly 8-15% slope that levels near the pond at the bottom of the slope. Forage growth was mediocre, and legume content was very low, when the field was assessed for the project in spring of 2012. Dorn Cox noted that the pond had previously served as their swimming pond. It had become overgrown with algae since 2009, indicating excess phosphorus availability in the water (Figure 2), despite the fact that manure-spreading buffers were attended to in accordance with their CNMP.

Figure 2. Pond field. At initial assessment in spring 2012, the former recreational pond was eutrophic. Heavy algal growth was visible at the edges (a). Grass forage growth was of low vigor, and forage legume content was very low (b). Photo credits: Dorn Cox and Bianca Moebius-Clune
Screen Shot 2014-09-16 at 11.53.52 AM

2. Goals and sampling

Goals for the farm included improving soil health, productivity, on-farm nutrient and carbon cycling, and long-term sustainability, and regaining use of the pond for recreational purposes. A number of representative fields on the farm were sampled to assess baseline status and to guide changes in management as the enterprises evolve.

3. Constraints: identified, explained, and prioritized

Overall, soil health at Tuckaway Farm was found to be medium to high, with generally high total organic matter and aggregate stability due to low tillage and long-term perennial forage growth. However, compaction was a prominent soil constraint. Severe surface compaction and suboptimal subsurface hardness were identified as factors driving decreased soil functioning and low current plant vigor in Pond Field (Figure 3), likely due to traffic on wet soils during haying and grazing. Active carbon was suboptimal or constraining in every field, likely resulting from low plant vigor and thus low fresh root and shoot contributions to soil organic matter. P, K and pH were suboptimal in many fields, including Pond Field, further contributing to low plant vigor and low legume content. Eutrophication problems from excessive P inputs into the pond were thus clearly not due to high soil P. Rather eutrophication was explained by poor physical and biological soil health. Severe compaction on a grazed slope with suboptimal vegetation growth was causing excessive runoff during rain events, and thus water quality problems.

Figure 3. 2012 Cornell Soil Health Assessment for Pond Field shows that compaction drives the lack of soil functioning observed for this field, with suboptimal nutrient and pH conditions contributing to poor plant growth, which in turn explains suboptimal active carbon availability.
Fig3

4. Feasible management options

Surface and deep targeted soil disturbance were identified as feasible and most promising options (see table of management suggestions) for alleviating compaction. Improved selection of cover and pasture crop species was considered secondary for this constraint, based on low vigor and the need to jump-start the system through initial loosening of the soil, but these selections were deemed essential for improving and maintaining biological activity in the longer term. Woodash and manure were identified as the most feasible immediate ways to address nutrient and biological activity constraints. It was noted that bedrock for the soil type is generally at 10-20”, so that improving water dynamics and preventing erosion was particularly important, but that bedrock proximity might cause challenges for mechanical compaction management in some areas.

5. Short and Long Term Soil Health Management Plan

The short-term management calendar included the following immediate remediation in August of 2012:

  • Deep ripping with the available Yeoman’s plow along slope contours (30” spacing, to maximum depth possible considering bedrock), to alleviate subsoil compaction, low infiltration, and erosion issues.
  • Interseeding tillage radish or similar deep rooted fall brassica in order to keep soil pores open, implemented in the same pass as the above if feasible.
  • Woodash application followed by aerway incorporation to address suboptimal K, P, and pH, along with surface compaction.

A combination of rotational grazing or haying during appropriate soil moisture conditions was recommended. Grazing was to be followed with aerway incorporation of manure to increase soil P and decrease chances of erosion. Interseeding of additional species, such as warm season annual forages (sorghum sudangrass or forage soybean) during 2013 was planned to increase biomass production and thus biological activity. Monitoring compaction levels and possible follow-up with further mechanical alleviation was planned for subsequent years.

6. Implement, monitor, and adapt

Implemented Practices: The plan was implemented with some adaptations due to farm scheduling, weather constraints and equipment availability (Figure 4). Yeoman’s plow and aerway with one hole offset were used according to plan, but no woodash was applied, nor were additional crops interseeded in the fall of 2012.  The three shank yeoman’s plow was set to 20” depth and 30” spacing between shanks, followed by the aerway with one-hole offset on the same day.  All grazing was stopped on the slopes above the pond starting in 2012.  Two cuts of dry hay were taken during the summer of 2013. The wet 2013 spring delayed woodash delivery and spreading until after the second cut hay was removed, and the spreader was available for covering multiple fields. Woodash was surface spread in October 2013 using the conservation district’s Stolzfus wet lime and woodash spreader loan program. The slope above the pond was then seeded to a hairy vetch, winter rye, wheat, barley mix in a single pass cultivation using a Unimog U1200 tractor with a front mounted Howard rotovator set to 3”, and rear mounted Great Plains no-till drill. The mix was planted to address surface compaction for improved infiltration, as well as to produce one of multiple potential crops depending on needs at harvest: feed grain, cover crop seed (usable as on-farm custom winter mix, or separable with the farm’s spiral separator), or a single cut of legume mix dry hay harvestable in late August of 2014.

Figure 4. Soil Health Management Plan Implementation: Deep ripping with a yeoman’s plow along the slope’s contours (a) to alleviate subsoil hardness, followed by Aerway treatment (b) to alleviate surface hardness in the fall of 2012. Wood ash application to alleviate low pH, and K and P deficiencies (c), followed by single pass shallow rotovator cultivation and seeding of grain-vetch mix (d) to further alleviate surface compaction and produce crop. Photo credits: Dorn Cox and Bianca Moebius-Clune
Screen Shot 2014-09-16 at 11.54.35 AM

Observed Results: Prior to implementation in 2012, significant runoff was evident during rain events. Algal growth (Figure 5a) prevented use for recreational purposes.  Water flow from the slope during rainfall was noticeably reduced after deep rip and aerway treatments, despite the wet 2013 spring, and the pond started to clear and became usable for recreation in 2013. Runoff reduction appeared even greater post grain-vetch-mix planting in the fall of 2013, and the pond’s water quality continued to improve into the 2014 summer season (Figure 5b, 5c). The effect of wood ash was evident in the spring of 2014 as vigorous clover growth returned to the field, and the grain-vetch mix grew with satisfactory vigor (Figure 5d). Progress in crop productivity and pond water quality will be monitored further.

Figure 5. Heavy algal growth as was seen along the pond’s perimeter in 2012 (a). Clear water (b), regained recreational use (c), and improved legume content and satisfactory crop vigor (d) after implementation of the first ~ 20 months of a situationally adapted Soil Health Management Plan.  Photo credits: Dorn Cox and Bianca Moebius-Clune
Screen Shot 2014-09-16 at 11.54.52 AM

Conclusions

In this case-study, a targeted set of soil health management practices were implemented to alleviate previously unidentified compaction, in addition to interacting minor biological and chemical constraints. These treatments have resolved eutrophication problems in a pond that can now again be used for recreation. This case demonstrates strong evidence for the need to move beyond simple Nutrient Management Planning, to more comprehensive Soil Health Management Planning. We illustrate interactions between nutrient-related constraints and biological and physical limitations in soil conditions: in this case the lack of infiltration from compaction and poor rooting allow for simultaneous occurrence of nutrient deficiencies in soil and nutrient excesses in water. We further illustrate the limitations of applying prescribed best management practices (e.g. buffers), as opposed to using environmental monitoring and systems indicators to provide feedback for adaptive nutrient management.  Biological and physical constraints must be explicitly identified through soil health assessment, and managed comprehensively alongside nutrient-related constraints. Management must be adapted in response to seasonal conditions and observations, in order to achieve satisfactory progress in soil and water conservation.

Acknowledgements

We would like to acknowledge funding received from a NH NRCS Conservation Innovation Grant, a Specialty Crops Block Grant, from the NH Charitable Foundation, and from NY Hatch, which enabled completion of this project. We would also like to acknowledge the collaboration of NH NRCS and Soil and Water Conservation District staff, and of additional NH growers, who helped inform the development through their participation in the planning process and contribution of diverse farm scenarios to test the flexibility of the framework.

 

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What’s Cropping Up? Volume 24, Issue 3 – Full Issue

Rye vs. Oat Cover Crops on a Manured Field: Environmental Benefits Vary Greatly

Chris Graham, Harold van Es, and Bob Schindelbeck, Department of Crop and Soil Sciences, Cornell University

Land application of manure creates conditions conducive for significant environmental losses of nutrients. Application of manure involves large amounts of the nutrients nitrogen and phosphorus, often resulting in excess residual levels – especially after dryer growing seasons. Losses are especially acute in the following winter and spring as excess water from snow melt and rain promotes runoff and erosion of P, leaching of nitrate, and emissions of nitrous oxide from denitrification.  The latter is a significant greenhouse gas concern.

Cover crops are increasingly adopted for various purposes, including to suppress weeds, reduce runoff and erosion, build soil health, provide nitrogen (from legumes), or immobilize leftover nitrates.  For manured fields, winter cover crops may have special benefits by limiting P losses through reduced runoff and erosion, and by scavenging residual N and making it unavailable for leaching and denitrification.

In this study, we tested the ability of oats (Avena sativa L.) and winter rye (Secale cereal L.) cover crops to reduce nutrient losses through multiple potential pathways during the early winter and spring season in a soil with a history of manure application.  Winter rye and oats were selected due to their popularity in the northeastern USA and also for their difference in winter tolerance.  Oats establish well in the fall but are winter killed in our climate, which eliminates the need to terminate their growth in the spring. Rye, on the other hand, survives through our winters and resumes active growth early in the spring. Both cover crops provide soil cover and take up residual N from the previous growing season, thereby reducing both N and P losses. We hypothesized that rye, as it growth longer into the fall and re-establishes in the spring, is more effective at reducing environmental losses than oats.

Methods

This study was conducted on a working dairy farm located in Central New York using a field with a recent history of manure application. The soil at the research site is an Ovid silt loam with 4% average organic matter content in the surface soil and pH of 7.1. During the previous three years, manure was applied in April 2008, October 2009 and April 2010 (final application before study commenced) at total N rates of 145, 170, and 100 lbs per acre, respectively.

Winter rye and oats were broadcast seeded on 24 September 2010 after corn silage harvest in a spatially-balanced complete block design at a rate of 100 lbs per acre. Along with control plots, each cover crop treatment was replicated four times for a total of twelve plots. Quadrats of rye and oats were subsequently harvested on 3 December, 2010 and analyzed for N uptake. The Roots were harvested to a depth of 6 inches.  Soil samples were taken on 3 December, 14 March, 7 April, and 28 April from the 0-to-6 and 6-to-12 inch soil layers for mineral N analysis. Also, on the latter two dates soil material was collected for measurement of nitrous oxide emission potential using a method involving simulated rainfall (to induce denitrification) and 96-hour incubation at the seasonal temperatures (50oF for 7 April and 60oF for 28 April).  Soil water was sampled at 20 inch depth using a tension lysimeter to determine the nitrate content.

Results

Table 1.

Cover Crop Biomass and N Contents

The rye cover crop produced much higher levels of biomass than the oats during the fall season after seeding, as measured on 3 December (Table 1). Aboveground biomass was three times greater in the rye plots than oats, as the former grew more vigorously and was not affected by frost kill. Larger surface biomass for rye implies that it provides greater benefits for reducing runoff, erosion, and P losses.  Also, rye nitrogen uptake was 23.5 vs. 8.7 lbs per acre (269% greater) compared to the oats.  On 28 April, the rye had accumulated more than twice the biomass compared to 3 December, but the total N uptake was similar (about 25 lbs per acre; Table 1).

Figure 1.

Nitrate Leaching

Cover crop effects on nitrate concentrations below the root zone (20 inch depth) were found to vary considerably (Figure 1). Rye significantly and markedly decreased NO3-N concentrations compared to the Control and Oats treatments. Concentrations under oats in fact were about the same as the plots without cover crop – basically indicating that they had no benefit for reducing leaching.  Throughout the spring season, average measured nitrate levels were 43, 52, and 1 mg NO3-N L-1 for the Control, Oat and Rye plots, respectively.

Figure 2.

Nitrous Oxide Emissions

While variability was high, both spatially and temporally, significant results were found in nitrous oxide emissions. Treatment effects changed as the spring season progressed (Figure 2). The Oats treatment produced similar results to the Control throughout the sample period while Rye decreased N2O emissions in late April after a high initial flux earlier in the month.  Higher emissions were measured at the early sampling from plots with cover crops, which had a relatively fresh carbon source that promotes denitrification. Reductions in the Rye plots later in April, were presumably the result of a smaller soil nitrate pool, as the rye cover crop had taken up much of the released N. Average emissions from the Rye treatment were roughly half of the Oats treatments during the final sampling.

Conclusions

The results of this study are clear:  During the winter and spring period when field N and P losses can be high, rye cover crops show great potential to mitigate negative environmental effects. The rye accumulated much greater biomass than oats in the fall, providing better winter cover to reduce runoff, erosion, and P loss potential. Rye also had a very strong positive impact on reducing nitrate leaching in the soil profile, as nitrate concentrations at 20 inch depth were extremely low throughout the sampling period. Oats showed no improvements in reducing nitrate leaching compared to the no-cover crop option.

Rye did not show reduced nitrous oxide emissions resulting from a simulated heavy rainfall event in early April, but showed a 70% decrease later in the month when it was actively taking up N and producing biomass. Oats had winter killed and therefore averaged consistently high emissions throughout the spring period.

In all, the rye cover crop had significantly greater positive effects in terms of reducing P and N loss potentials, while the benefits of the oats were minimal. Although results may vary seasonally, the winter hardy rye cover crop should be given strong preference over oats when the primary objective is to reduce nutrient losses to the environment.

Acknowledgements:  This research was supported through a grant from the USDA Northeast Region Sustainable Agriculture Research and Education program.  We are grateful for the collaboration of John Fleming of Hardie Farms in Lansing, NY.

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