Category: Nutrient Management

Bianca Moebius-Clune, Harold van Es, and Jeff Melkonian, Department of Crop and Soil Sciences, Cornell University

Research has demonstrated (summarized by van Es et al., 2007) that soil and crop management practices, combined with weather conditions during the early growing season, greatly affect N losses and are therefore critical factors in determining optimum N rates.  The difference in fertilizer N needs from one year to the next could easily be 100 lb N, and generalized N recommendations are inherently imprecise. In a recent case study, we highlighted the impact of early- vs. late planting on recommended N rates (What’s Cropping Up?, Vol. 21, No 4).

It is not possible to accurately determine at the beginning of the growing season how much N fertilizer will be needed for that year’s crop, because some critical processes that affect N losses have not yet passed.  Most growers fertilize for a worst-case scenario and apply “insurance fertilizer” – they put on in excess of what is needed in most years. This reduces farm profits and causes high environmental losses.  Seasonal corn N needs can be estimated much better in the late spring to guide sidedress applications.  Adapt-N is an online decision support tool (http://adapt-n.cals.cornell.edu) designed to help farmers precisely manage nitrogen (N) inputs for grain, silage, and sweet corn. It uses a well-calibrated computer model, and combines user information on soil and crop management with high resolution weather information, to provide N sidedress recommendations and other simulation results on nitrogen gains and losses. We have completed the first year of beta-testing through on-farm strip trials in New York, which are presented in this article.

Methods
We completed 18 replicated strip trials on commercial and research farms throughout New York during the 2011 growing season. They involved grain and silage corn, with and without manure application, and different rotations (corn after corn, corn after soybean, and corn after a clover cover crop; Table 1). Treatments involved two rates of nitrogen, a conventional “Gower-N” rate based on current grower practice and an “Adapt-N” recommended rate.  A simulation was run for each field prior to sidedressing to determine the Adapt-N rate. In 2011, due to seasonal weather conditions, all Adapt-N rates were lower than conventional N rates (by 15 to 140 lbs/ac; Table 1).  Growers then implemented field-scale strips with 3 or 4 replications for each treatment (except NY8 and NY9, where only single yield strips were implemented due to time and equipment constraints).

Yields were measured by weigh wagon, yield monitor, or in a few cases by representative sampling (two 20 ft x 2 row sections per strip). Partial profit differences between the Adapt-N recommended and Grower-N management practices were estimated through a per-acre partial profit calculation:

Profit = [Adapt-N yield – Grower-N yield] * crop price – [Adapt-N  N use – Grower N use] * price of N

Yields were used as measured, regardless of statistical significance, since the statistical power to detect treatment effects is inherently low for two-treatment strip trials. For corn, a grain price of $5.50/bu was assumed ($6.50/bu minus $1.00/bu for drying, storing and trucking from PA Custom Rates; USDA, 2011). For silage, $50/T was assumed based on reported NY silage prices of $25-75/T. The price of N fertilizer was assumed at $0.60/lb N (prices ranged from $0.49 – $0.75/lb N in NY). Total N losses to the environment (atmosphere and water) and N leaching losses were estimated for each treatment by running model simulations with all N inputs through the end of the growing season (30 October). Agronomic, economic and environmental outcomes of these trials were then used to assess Adapt-N performance.

Results
Errors were made in model and/or trial implementation in a few cases (labeled with * in Table 1):  A clover cover crop was improperly simulated as an incorporated sod, resulting in a low Adapt-N recommendation and substantial yield losses. In other cases, Adapt-N fertilizer and manure inputs did not reflect real field applications, or N applications were made too late in the season.  The lesson here is that correct input information is, of course, needed for Adapt-N to provide an accurate recommendation.  The resulting yields and simulations from the above four trials were not representative of 2011 Adapt-N performance, and these trials were therefore removed from further analysis.

Agronomic, economic and environmental comparisons between Grower-N and Adapt-N treatments for each trial are provided in Figure 1, and as averages in Table 2. A comparison of grain and silage harvest data (Fig. 1a & 1b) shows that differences in yields were negligible and statistically not significant for almost every trial, despite substantially reduced N rates applied for the Adapt-N treatment (Tables 1 and 2).  A case study describing one of these trials, conducted at Donald & Sons Farm, in Moravia, NY, where 140 lb of N were saved without yield loss, is described in a companion article in the current issue of What’s Cropping Up?.

When the previous crop was soybean (3 trials), yield losses were found in every case (Fig. 1a), although the grower N rates were well above economic optimum N rates. We determined that Adapt-N overestimated the soybean N contribution, and thus provided low N recommendations in these three cases. The 2011 version of Adapt-N used a flat 30 lb soybean N credit, but also simulated immobilization of N in stover in corn-after-corn rotations, effectively almost doubling the N credit for corn following soybean.  We believe that part or all of the soybean ‘N credit’ should mostly be regarded as an absence of an immobilization penalty for corn-corn rotations. Changes will be made to the Adapt-N tool to reflect these findings for the 2012 growing season.

Estimated leaching losses (Fig. 1c & d), as well as total N losses (Table 2) decreased as a result of reduced N application rates for the Adapt-N treatment. On average, leaching losses decreased by 38 lb N/ac in grain trials, and by 11lb/ac in silage trials. There was less room for improvement in silage trials because lower fertilizer rates were used after manure applications.

Most trials resulted in profit gains from the use of Adapt-N, ranging from $1 – $80/acre, (Fig. 1e & f). Average profit gains were $35/acre for corn after corn and $39/acre for silage corn (Table 2). Corn after soybean trials registered an average loss of $11/acre due to one trial with high yield loss (NY3). This was the only trial out of 14 (7%) where profit loss was significant.  Fig. 2 indicates the low risk of profit loss (<14% overall before the correction of the soybean N credit), and high probability of improved profits (86%) of using Adapt-N in 2011.

Our data suggest that after minor adjustments of the Adapt-N tool, it will be even better equipped to give accurate recommendations.  Growers who tend to use high amounts of nitrogen will realize large savings. In a much wetter year, increased profitability would come from appropriately applying more N at sidedress time in order to prevent yield reductions from N losses.  In the long term we expect that environmental losses will decrease in both dry and wet years, because this tool provides strong incentives to shift  N applications to sidedress time.

Conclusions
From beta-testing on commercial farms throughout NY State in 2011, we determined that the value of the Adapt-N tool was substantial. The tool was quite successful in adjusting for the effects of seasonal conditions to accurately recommend N fertilizer needs.  Also,
• N application rates were significantly reduced (15         to 140 lb/acre).
• Grower profits increased on average by $35/acre, except in corn after soybean (due to model inaccuracies that are being corrected for the 2012 growing season).
• N losses to the environment were decreased substantially (5 to 120 lb/acre).

Adjustments to the Adapt-N tool will improve ease of use and accuracy for the 2012 growing season. The Adapt-N tool and information about it is accessible to stakeholders through any device with internet access (desktop, laptop, smartphone, and tablet) at http://adapt-n.cals.cornell.edu/, where information on account setup is also available.

Acknowledgments
This work was supported by grants from the NY Farm Viability Institute and the USDA-NRCS Conservation Innovation Program.  We are grateful for the cooperation in field activities from Bob Schindelbeck, Keith Severson, Kevin Ganoe, Sandra Menasha, and Anita Deming of Cornell Cooperative Extension, from Dave DeGolyer, Dave Shearing and Jason Post at the Western NY Crop Management Association, and from Eric Bever and Mike Contessa at Champlain Valley Agronomics. We also are thankful for the cooperation of the many farmers who implemented these trials.

References
van Es, H.M., B.D. Kay, J.J. Melkonian, and J.M. Sogbedji. 2007. Nitrogen Management Under Maize in Humid Regions: Case for a Dynamic Approach.  In: T. Bruulsema (ed.) Managing Crop Nutrition for Weather. Intern. Plant Nutrition Institute Publ. pp. 6-13. http://adapt-n.cals.cornell.edu/pubs/pdfs/vanEs_2007_Managing N for Weather_Ch2.pdf. [URL verified 2/22/12].

EPA, 2010. Inventory of U.S. Greenhouse Gas Emissions and Sinks (1990-2008). U.S. Environmental Protection Agency, Washington, DC.

Marlene van Es (1), Bianca Moebius-Clune (1), Harold van Es(1), Jeff Melkonian(1), and Keith Severson (2), (1) Department of Crop and Soil Sciences, Cornell University and (2) Cornell Cooperative Extension Cayuga County

Growers across the country have used a wide range of methods to decide on nitrogen (N) application rates for corn, from mass balances to a variety of soil and plant tissue tests, to maximum return to nitrogen curves, to… simply… rules of thumb. But most are frustrated by the lack of accuracy of these methods.  Early-season weather can greatly impact how much N fertilizer is needed year to year, and this variability has been difficult to manage. The amount of N fertilizer required could easily differ by 100 lbs from one year to the next. This variability results in average N recommendations that are higher than needed in many years, leading to profit loss for growers and environmental damage through N losses to water as nitrate and to the air as nitrous oxide, a potent greenhouse gas.

The web-based Adapt-N tool has the potential to change the way N management is done. Soil data, along with crop and soil management information are supplied by the grower. The Adapt-N tool uses these data in combination with newly available high-resolution climate data to simulate N availability and losses due to weather, and thus provide more accurate sidedress N recommendations. The tool is undergoing beta-testing in on-farm strip trials across New York and Iowa in the 2011 and 2012 growing seasons. Once fully validated, Adapt-N will, over the long term, help reduce N losses to the environment that contribute to air and water pollution, while saving farmers money through the optimization of fertilizer purchases and application rates.

One of the New York agricultural enterprises collaborating with the Adapt-N team is Donald and Sons Farm located in Moravia, NY. The farm has been in the family for several generations and currently encompasses 1500 acres of land. In 2011, 1050 acres were in corn and 250 in soybeans.

The Donald brothers, Robert and Rodney, are no strangers to on-farm research and have collaborated with Cornell University and private companies many times over the years.  When asked why they keep getting involved in research Rodney replied, “Money! Some [projects] take you down a dead end street, but if we see, for example, that we can save putting 100 lbs [of N] on, that’s a lot of money.” So, although the on-farm research can be time consuming for Robert and Rodney, they see the value in the important benefits it can generate.

The Donald brothers’ acreage varies greatly in soil type, and organic matter contents range from about 1 to 5%. The farm currently bases its N application rates on recommendations from A&L Great Lakes Laboratories, generated based on soil tests by management unit. Robert and Rodney practice variable rate application, taking advantage of their RTK-GPS system for soil sampling, input application and yield monitoring. The bulk of their fertilizer N application occurs at sidedress time, as they have found that early season applications run the risk of losses during wet springs. They experimented for a few years with putting anhydrous ammonia on at preplant, and considered slow-release and inhibitor technology, but decided to return to sidedressing. The amount the Donalds spend on N fertilizer has nearly quadrupled since 2000, and in 2011 they spent $107,000 – a strong incentive for them to seek new tools to help optimize application rates. As Rodney puts it, “money talks … and with what we are getting in corn for what we are putting on in ammonia, we’re not gaining.”

This past spring, Robert and Rodney identified 10 acres of a 100-acre field to implement a replicated strip trial to test the Adapt-N tool. The field was planted with corn on May 21st with 22lbs of N from monoammonium phosphate starter. In early June, Keith Severson of Cayuga Cooperative Extension used Adapt-N, inputting the Donald brothers’ field information, such as organic matter content, expected yield, tillage, fertilizer inputs, etc., to generate an N sidedress recommendation of 80 lb N/acre.

When asked what he thought when he heard of the 80 lb recommendation, Rodney said, “it was hard for me to chew on 80. … It was a little hard for me to chew on!” On June 19th, two sidedress treatments were applied in eight, 16-row-wide strips. Four of the strips received the standard N rate based on the recommendation from A&L labs, which was 220 lbs, and the remaining 4 strips received the Adapt-N rate of 80 lbs. Throughout the growing season, the brothers still felt very unsure about the low Adapt-N rate compared to their usual practice. They kept their eyes on the field after sidedressing, taking note that the Adapt-N strips appeared to be a lighter shade of green. “We thought, uh oh, this is going to be a blow, here we go.”

However, as the season came to a close the results indicated otherwise. There was no loss in yield despite the 140 lb application rate difference. The Donald’s yield monitor data showed spot-yields between about 120 and 230 bu/ac. The average yields for the conventional plots were 174.1 bu/ac, while Adapt-N average yield was 173.6 bu/ac. Robert and Rodney were shocked by the results stating, “it wasn’t until we were combining that we realized the yield wasn’t really different even though there was a 140 lb N difference [in sidedress rate]”.

The results show great promise for the Adapt-N tool and for the Donald brothers’ ability to save on N fertilizer. Assuming that the trial field was fairly representative of the rest of the farm, the Donalds would have saved approximately $70,000 in fertilizer in 2011.  A post-season Adapt-N simulation estimated that they had also reduced their N leaching losses in 2011 by about 77%, from 142 to 32 lbs/ac.

Robert and Rodney intend to collaborate on more extensive testing of the Adapt-N tool next year and see whether different weather conditions affect the recommendations. In addition to another fully replicated strip trial, they may use variable-rate recommendations provided by Adapt-N in strips next to those provided by A&L Laboratories on multiple fields. When discussing variable rate application with the brothers, using rates with drastically higher N amounts than needed by the crop was likened to “aiming for the bull’s eye in the opposite direction of the target,” to which Rodney laughingly replied, “I’ve been doing that all my life.” Variable rate application using Adapt-N should allow for a more accurate AND precise accounting of the effects of organic matter-derived N and texture in interaction with that year’s weather on overall N availability.

Overall the trial suggests that more accurate N recommendations based on weather impacts, in addition to soil and management information, could lead to substantially higher profits for farmers, while reducing environmental losses in most years. This creates a win-win situation as farmers face higher costs for fertilizer and we search for feasible and effective ways to reduce detrimental losses to the environment.

Acknowledgments
This work was supported by grants from the NY Farm Viability Institute and the USDA-NRCS. Thank you to Robert and Rodney Donald for their cooperation in diligently implementing this trial, and taking the time to share their thoughts.  For more information about the Adapt-N tool, visit http://adapt-n.cals.cornell.edu/.

Quirine Ketterings¹, Greg Godwin¹, Charles L. Mohler², Brian Caldwell³, Karl Czymmek^1
1Department of Animal Science, and ²Department of Crop and Soil Sciences, Cornell University, ³Department of Horticulture, Cornell University

Red clover undersown into a small grain crop is commonly used as an N source for corn in organic grain production systems. How much N should be credited to the clover green manure is unclear. In this study we addressed the following issues: (1) ammonium and nitrate dynamics over time following clover plowdown; (2) release peak for nitrate related to the above ground biomass in the clover; and (3) clover plowdown influence on the results of the Illinois Soil Nitrogen Test (ISNT), a predictor of soil N supply potential. Results from earlier years were reported in Godwin et al (2009) and Ketterings et al (2011). Here we report the 4-year summary.

Methods
We monitored ISNT-N, ammonium-N and nitrate-N levels on a weekly basis in corn crops in one management system within the Cornell Organic Grain Cropping Systems Experiment at the Musgrave Research Farm near Aurora, New York. Beginning in 2005, this experiment has compared five management systems with differing fertility and tillage regimens and two entry points into a soybean-spelt/red clover-corn rotation (http://www.organic.cornell.edu/ocs/grain/index.html). For the project discussed here we sampled the Low Input Organic System (System 2) during years when corn was grown following plowdown of a 1-yr old clover cover crop.

Actual fertility amendments and their date of application are shown in Table 1. Plots were randomly split into two rotation entry points, so that one half of each plot was a year behind in the crop rotation sequence. The plots that were sampled for N dynamics were part of Entry Point A in 2007 and 2010 and Entry Point B in 2008 and 2011.

Prior to plowing, we collected samples of above-ground clover biomass. Below-ground biomass was also sampled in 2011. The initial soil sampling round (0-8 inch depth; 12 cores per 120’ x 40’ plot) occurred prior to plowdown of the clover. The next sampling round occurred at plowdown and was followed by eight sampling rounds at weekly intervals thereafter (seven in 2011). Corn was planted in late May or early June (Table 2). On New York organic grain farms corn is generally planted in late May with the goal of planting into warm soils to achieve optimal germination without the need for seed protectants, and to allow for sufficient clover growth to support the N needs of the corn crop.

Soil samples were analyzed for ISNT-N in the Cornell Nutrient Management Spear Program (NMSP) laboratory using the enclosed griddle modification of Klapwyk and Ketterings (2005). Soil samples were also analyzed for 2 N KCl extraction of exchangeable nitrate+nitrite and ammonium as described in Mulvaney (1996). The weather patterns showed two extreme rainfall events during the sampling periods: a 2 inch plus rainfall event in week 4 after planting in 2010 and another in week 5 in 2011 (Table 3).

Results and Discussion
Clover above-ground dry biomass was 1.6, 2.4, 1.5 and 1.7 ton/acre in 2007, 2008, 2010 and 2011, respectively. In 2011 the below ground cover crop biomass was 0.6 ton/acre, about 25% of the total (above and below ground) biomass of the clover cover just prior to plowdown. The year 2007 was a drought year with low corn yield (87 bu/acre), whereas 2008 and 2010 were excellent growing years (165 bu/acre in 2008 and 160 bu/acre in 2010). Despite challenging growing condition (wet spring and fall, dry mid-summer) yield averaged 150 bu/acre in 2011.

Soil nitrate-N levels increased following clover incorporation (Figure 1). The height of the nitrate-N peak following plow-down was consistent with clover biomass over the four years: just over 60 ppm in 2007, almost 90 ppm in 2008, and about 30 ppm in 2010 and 2011 (Figure 1). Peaks in nitrate-N were measured in week 3 in 2011 and 5 or 6 in all other years. The timing of nitrate-N release from clover was well-aligned with the period of highest corn N needs in 2007 and 2008. In 2010 and 2011, the heavy rainfall in week 4 (2010) and week 5 (2011) may have leached nitrate-N. Nitrate leaching may be the cause of the relatively low nitrate release peaks in 2010 and 2011.

Soil samples were analyzed for ISNT-N as an indicator of soil N supply potential through mineralization of organic matter. Previous work has shown that the test is accurate as a predictor of soil N supply potential for corn but that soil samples should not be taken within 5 weeks after manure addition or sod turnover; these amendments create a temporary increase in ammonium-N and hence also in ISNT-N. The question remained whether incorporation of a cover crop would result in a similar restriction in timing of sampling for ISNT-N. The results of the four years of testing showed that clover incorporation did not result in an accumulation of ammonium-N and hence it is also not surprising that the ISNT-N levels remained stable over time (coefficients of variation across sampling dates were only 4.3, 2.2, 3.9, and 2.6% for 2007, 2008, 2010, and 2011, respectively). These results suggest that for the clover-based system, timing of ISNT sampling is not restricted (i.e. sampling can occur before or after clover incorporation). The comparisons of ISNT-N in 2007 and 2010 (entry point A) and 2008 and 2011 (entry point B) suggest a slow decline in ISNT-N over time under current management and yield levels (Figure 2) but additional research (more data points in time) is needed to evaluate trends.

Averaged across plots, the pre-sidedress nitrate test (PSNT) results were 20, 29, 16, and 17 ppm where clover had been plowed down in 2007, 2008, 2010, and 2011, respectively. There was a strong correlation between clover above-ground N pool prior to plow down and PSNT in this study (PSNT (ppm) = 4.9 + 0.14 * Npool (lb N/acre); R2 = 0.94). Additional data points are needed before conclusions can be drawn about the use of above ground N pool as a predictor of PSNT-N and the impact of weather on the predictions.

The weekly sampling and the PSNT results of the clover systems suggest that the clover supplied a considerable amount of N. Application of 1900 lb/acre of 4-5-2 poultry manure compost in addition to the plowed down clover in the same experiment showed no yield increase in 2007-2010 (Caldwell et al., 2011) or 2011 (data not yet published), suggesting that in each of the four years, the nitrate-N released from clover decomposition was sufficient to meet the needs of the corn, despite the <21 ppm PSNTs in 2007, 2010, and 2011.

Summary and Conclusions
Clover incorporation greatly increased the amount of available N for the following corn crop. Decomposition of the clover resulted in nitrate peaks 5-6 weeks after incorporation, well-aligned with N needs of the corn and showing that clover plowdown is an excellent choice for providing N to corn in organic and conventional production systems. Clover decomposition did not result in ammonium-N accumulation. This study needs to be duplicated at other locations but results to date indicate that a clover cover crop can supply sufficient N. although actual N supply will vary depending on the biomass produced and mineralization conditions. The study also showed that ISNT sampling for assessment of soil N supply is not restricted in time where clover is a main source of N fertility.

References

1. Caldwell, B, C.L. Mohler, Q.M. Ketterings and A. DiTommaso (2011). Yield and profitability during and after transition in the Cornell organic grain cropping systems experiment. What’s Cropping Up? 21(2): 7-11.
2. Godwin, G., Q.M. Ketterings. C.L. Mohler, B. Caldwell, and K.J. Czymmek (2009). Impact of clover incorporation and ammonium nitrate sidedressing on ammonium, nitrate, and Illinois Soil Nitrogen Test dynamics over time. What’s Cropping Up? 19(3): 12-15.
3. Ketterings, Q.M., G. Godwin, C.L. Mohler, B. Caldwell, and K.J. Czymmek (2011). Impact of clover incorporation and ammonium nitrate sidedressing on Illinois Soil Nitrogen Test dynamics over time 3-year summary What’s Cropping Up? 21(2): 1-4.
4. Klapwyk, J.H., and Q.M. Ketterings (2005). Reducing laboratory variability of the Illinois soil N test with enclosed griddles. Soil Sci. Soc Am. J. 69: 1129-1134.
5. Mulvaney, R.L. (1996). Nitrogen-Inorganic Forms. In Methods of soil analysis. Part-3- Chemical Methods. SSSA, Inc., ASA, Inc. Madison, WI. P. 1123-1184.

Acknowledgments
This work was supported by the USDA Organic Research and Extension Initiative, the New York Farm Viability Institute, and funds from the Cornell Experiment Station. We thank Kreher’s Poultry Farms for donating compost. For questions about these results contact Quirine M. Ketterings at 607-255-3061 or qmk2@cornell.edu, and/or visit the Cornell Nutrient Management Spear Program website at: http://nmsp.cals.cornell.edu/.

Quirine M. Ketterings, Greg Godwin, Sheryl N. Swink, Joseph Foster, Eun Hong, Karl Czymmek, Carl Albers, Peter Barney, Brian Boerman, Stephen Canner, Paul Cerosaletti, Aaron Gabriel, Mike Hunter, Tom Kilcer, Joe Lawrence, Eric Young, and Alex Wright

Background
Initial studies at a Western New York State dairy farm showed that for corn fields with a recent manure history, starter nitrogen (N) fertilizer could be eliminated without losing yield or reducing forage quality. Eliminating starter N on corn fields with a manure history has the potential to deliver significant savings of time and money to dairy producers. In 2009, we initiated a 3-yr project to test the need for starter N fertilizer across a range of New York State soil types and growing conditions. The objective of this study was to assess differences in yield and forage quality between corn that receives starter N fertilizer and corn that does not, on fields with varying manure history. Here we report the 3-year summary for sites completed without external challenges (weed control, bird damage, planter issues, harvest challenges, etc.). The final dataset included 21 trials, distributed throughout New York State.

Materials and Methods
Each trial included four replications or more of two treatments: 30 lbs N/acre in the starter versus no N in the starter. In 2009, seven trials were completed, including three trials at commercial farms and four at the Aurora Research Farm (sites 1 through 7). In 2010, starter N response trials were established at ten commercial farm locations and repeated at the Aurora Research Farm (sites 8–21). In 2011, an additional seven sites were established on commercial farms. Across all trial years, a total of seven trials were lost due to planter issues, excessive moisture interfering with planting and/or harvest, bird or deer damage, weed pressure, excessive variability, or uncertainty about the actual treatment allocation. All other trials (21 sites) are included in this summary.

Results
Eleven sites had an ISNT-N level classified as “deficient in soil N supply potential” (>7% below the critical value), five sites were “marginal in soil N supply potential” (within 7% of the critical value) while five sites were “optimal in soil N supply potential” (ISNT-N >7% above the critical value).

Across all three years, of the fields with optimal soil N supply potential (sites 19, 20, 21, 23, and 25), the manure application alone was sufficient to meet the N needs of the crop; none of these three locations showed a yield increase with starter N use (Table 1). The CSNTs (Table 2) confirmed N was not limiting yield at these sites, and for two locations (20 and 21) showed sidedress application rates can be reduced if not eliminated. Used in this way, the data suggest that the ISNT can help identify fields that will not benefit from starter or sidedress N.

Of the five sites that were classified by the ISNT as marginal in soil N supply potential, all received manure and only one (site 31) responded to starter N. The CSNTs were classified as optimal (sites 13, 31, and 35) or excess (sites 3 and 14), indicating that the fields received sufficient or more than sufficient N (Table 2). However, the lowest CSNT was measured for the site that had the yield response to starter N, suggesting an adjustment in CSNT interpretation is needed (inclusion of a 250–750 ppm “Marginal” range). We conclude for these five locations that manure application can replace starter and sidedress N for soils with a marginal soil N supply potential, as long as sufficient N is added with the manure. The results of site 31 also suggest that in some years a response to N can be expected where CSNTs are <750 ppm.

The sites classified as deficient in soil N supply potential (i.e., soil N alone is not expected to supply sufficient N for the corn crop that year) included the trials at Aurora with either no manure history (sites 6 and 11), or with limited manure history (sites 4, 5, 7 in 2009, and 9, 10, 12 in 2010) plus three on-farm locations (sites 8, 15, and 16). The results at sites 6 and 11 (significantly higher yields in 2010 with starter N and a similar though not statistically significant trend in 2009) suggest that starter N is needed for fields that do not have an optimal soil N supply as measured by the ISNT and are managed without manure. The results at site 11 also suggest that a response to N can be expected if CSNTs are <750 ppm (high producing year on deficient ISNT soil), consistent with the results of site 31.

At the other 3 sites at the Aurora Research Farm (4, 5, 7 in 2009; 9, 10, 12 in 2010), liquid manure had been applied at a rate of ~8,000 gallons/year over the past 5 to 6 years. Manure application increased ISNTs over time (compare values to sites 6 and 11), but after 5 to 6 years of manure application, the ISNT of these sites was still classified as deficient. Of these six site*years, three showed a significant yield increase with starter N addition, while a similar trend was seen for the other three sites (Table 1). These same sites exhibited deficient CSNTs (Table 2), suggesting that the specific manure history was not enough to increase soil N supply to levels high enough to supply the N needed by the crop and that the current year manure applications were also insufficient to meet N needs of the crop. Under these conditions, the starter N application was needed.

Of the remaining three on-farm sites with low soil N supply potential, two sites had CSNTs in the optimal range (without starter). A lack of a yield response to starter N illustrated that for these locations, the current year manure supplied sufficient N and starter N was not needed. The very high CSNT of site 15 >5000 ppm) suggests a reduction in sidedress N application was possible without an impact on yield or quality.

Of the silage trials, two locations showed a significant increase in crude protein with starter N addition (sites 3 and 21) while at one site, crude protein declined with starter N addition (site 25). Soluble protein increased at two locations, although the difference was very small (an increase of 0.3 and 0.1% in soluble protein at sites 3 and 16, respectively) and decreased at one site (site 25). Only one site showed a change in NDF (decrease, site 21). At one site, NDF digestibility increased with starter N addition (site 23) while at two additional sites, NDF decreased with starter N addition (sites 31 and 35). Lignin and starch were not impacted at any of the silage trials. Elimination of starter N did not result in significant differences in milk per acre estimates except for at one site where starter use decreased milk per ton (site 25, results not shown). Milk-per-acre estimates were only impacted at one site (increase at site 31, consistent with the yield increase upon starter N use).

Sites 6 and 11 (the only deficient ISNT sites without a manure history) illustrate that starter N will be needed even if sidedress N is applied. This scenario applies to cash grain operations without manure histories. Under those conditions, the best management practice is to use starter N (20-30 lbs N/acre) and sidedress to meet crop N needs. Omission of starter N is not recommended for fields without a manure history (deficient ISNT-N).

Sites that were classified as sufficient in ISNT-N included sites 19–25 (5 sites). None of these five sites showed a yield response to starter N addition. We conclude that if the ISNT is classified as sufficient, manure can be used to replace starter N.

Manured sites that were sidedressed (sites 15, 20, 21, 25, and 35) all had CSNTs that were optimal or excessive. Starter N use did not increase yield at any of these locations. Optimal or excessive CSNTs at each of these five locations suggest that sidedress N could have been eliminated or application rates reduced at these locations. These results suggest that starter N can be omitted for sites with a manure history even if the ISNT is deficient or marginal, as long as sufficient N from manure and other sources (rotations, soil N, sidedress N) is available.

Sites that had a manure history but were classified as deficient in N based on the CSNT included sites 4–5, 7, 9–10 and 12 (6 sites). Of these sites (all Aurora Research Farm sites with some but limited manure application history), sites 5, 9, and 12 showed higher yields when starter N had been applied than where corn was planted without a starter, with similar trends at sites 4, 7, and 10 (all Aurora Research Farm sites). The ISNT for each of these Aurora Research Farm sites was classified as deficient, suggesting additional N was needed. These results indicate a response to starter N is likely if ISNT-N is deficient and additional N applied is insufficient.

The tool available to determine whether or not the overall N addition was sufficient is the CSNT. The yield results of sites 11 and 31 (locations with an average CSNT between 250 and 750 ppm plus a significant yield difference upon use of starter N), suggest that a new interpretation should be added for 2nd or higher year corn: “Marginal” (250–750 ppm), where a response to starter N could be expected in wet years.

Main Conclusions

• Starter N should be used for fields with no manure history and no current year manure applications (deficient ISNT-N).
• If the ISNT-N is classified as optimal, manure can be used to replace starter N without a yield or quality decline.
• Manure can replace starter N for sites deficient or marginal in ISNT-N as well, but only if sufficient N from manure and other sources (cover crops, soil N, sidedress N) is available (CSNTs between 750 and 2000 ppm); a yield response to starter N would have been likely if the ISNT-N was deficient and additional N applied was insufficient as well.
• A new interpretation should be added for the CSNT for 2nd or higher year corn: “Marginal” (250–750 ppm), where a response to starter N could be expected in some years. To reduce risk, it is recommended that farms strive for CSNTs between 750 and 2000 ppm, using 8-inch stalks taken between 6 and 14 inches above the ground.
• We recommend producers analyze 2nd or higher year corn fields for both ISNT-N and CSNT, to identify sites where a starter N application can be omitted.

Acknowledgments
The project was funded with federal formula funds and Northern New York Agricultural Development Program (NNYADP) funds. We thank the farmers for participating in the project. Questions about this project? Contact Quirine M. Ketterings at 607-255-3061 or qmk2@cornell.edu, and/or visit the Nutrient Management Spear Program website at: http://nmsp.cals.cornell.edu

Julia Knight¹, Patty Ristow¹, Graham Swanepoel¹, Karl Czymmek^1,2, and Quirine M. Ketterings_^1
1Nutrient Management Spear Program, ²PRODAIRY, Department of Animal Science, Cornell University

Introduction
A policy interest in regional nutrient balances and farm interests in the value of manure inspired a study to begin understanding and characterizing the current state of manure exports and imports in New York State (NYS). Initial discussions with producers, farm advisors, and policy makers showed a need for more information on (1) the current movement of manure between dairy and crop farms, and (2) the (perceived) value and costs of manure handling for both dairy and crop farmers. The purpose of this study was to obtain information about current manure use, transfers, drivers and limitations, and the value of manure as perceived by crop and dairy producers.

Farmer Surveys
Surveys (postcards, see Figure 1) were handed out across New York (NY) during fifteen farmer meetings held between January 1 and March 31, 2010. Overall, 266 surveys were
completed (200 dairy and 66 crop producers) representing 38 NY counties, and 7 counties from Vermont, Connecticut and Maine.

Main Findings
Among those surveyed, the average dairy farm had 295 cows with 625 acres of cropland. The average crop farm was 1030 acres. Across dairy farms, 86% of the acreage received manure (535 acres out of 625 acres of the average dairy farm), 47% had at least 6 months of manure storage.

All of the farms with 700 or more cows (17 farms) tested manure at least annually versus 40 of 53 farms (75%) for farms with 200-699 cows. At farms with 100-199 cows, manure was tested annually by 10 of 34 farms (29%) and once every 2-3 years by 17 of 34 farms (50%). Of the farms with less than 100 animals, 66% never tested manure for nutrient content (Figure 2).
Manure was exported off the farm by 20% of the 200 dairy producers that were surveyed. The most important reason for not exporting (more) manure was the perceived lack of manure to meet crop nutrient needs at the dairy farm itself (Table 1).

Of the crop producers surveyed, 64% reported that they apply manure to an average of 41% of their crop acres, indicating manure export from dairy farms to crop farms is occurring in the region. Crop producers who did not import manure indicated lack of availability and concerns about compaction as the two main reasons to limit manure use on their farm (Table 2). Odor and costs were seen as less of a concern.

Both dairy and crop producers listed organic matter and nutrients as the most valuable manure properties (Tables 3 and 4). Enhanced soil water holding capacity (moisture retention) with manure use was considered less important.

There was a gap between the perceived value of manure by dairy producers and by crop producers. Dairy
producers on average priced manure at a value of $96 per acre with a range of $20 to $400 per acre while crop producers on average valued manure at $53 per acre with a range of $0 to $150 per acre, respectively.

Of those crop farmers that applied manure, only 21% indicated they had paid for the manure. The average payment per acre manure applied was $88/acre. Dairy producers estimated their actual manure handling and application costs to amount to $43/acre (averaged across the farms).

Manure nutrient distribution to non-dairy cropland is taking place in the region. However, many of the dairy farms (160 out of 197) did not export manure (Figure 3). The percentage of farms that export manure increases with an increase in animal density with a third of the farms exporting manure when animal densities exceeded 0.75 animal units per acre (1 animal unit equals 1000 lbs).

Preliminary Interpretations
Nitrogen management (timing and application method) choices can have a large impact on how much manure must be applied per acre to meet crop N needs. When less efficient N management practices (such as surface application without incorporation) are utilized, the P addition with the manure can substantially exceed crop P needs leading to greater P losses and/or accumulation in the soil. If dairies are able to improve N use efficiency of manure and fertilizer and/or add N from other sources (cover crops, greater reliance on N fixation, shorter rotations, building of soil organic matter levels through use of reduced tillage practices, etc.), they may have more manure available to move off the farm. More efficient manure N use coupled with increased manure distribution across the landscape has the potential to improve regional P balances and with increasing fertilizer prices, farms may be able to derive value from such transactions in future years

Conclusions
The survey results indicate crop and dairy producers value manure, mostly for its supply of nutrients and organic matter. Crop producers tended to place a lower monetary value on manure than dairy farmers which may reflect a deeper understanding by dairy farmers of the value of manure as a fertilizer replacement. The results of this survey reflect that manure export/import activities are currently limited by manure availability and a gap between the perceived dollar value of manure by dairy producers and by crop producers. However, the responses also indicate the potential for greater export from higher density dairy farms to crop farms in the future, as both groups share recognition of the benefits of manure.

Acknowledgments
This work was sponsored by the Center for Dairy Excellence and the New York Farm Viability Institute. We thank the many Cornell Cooperative Extension educators who helped with the surveys. Questions about this project? Contact: Quirine M. Ketterings at 607-255-3061 or qmk2@cornell.edu, and/or visit the Nutrient Management Spear Program website at: http://nmsp.cals.cornell.edu/.