Sarah E. Lyonsa, Quirine M. Ketteringsa, Shona Orta, Gregory S. Godwina, Sheryl N. Swinka, Karl J. Czymmeka,b, Debbie J. Cherneyc, Jerome H. Cherneyd, John J. Meisingere, and Tom Kilcera,f
a Nutrient Management Spear Program, Department of Animal Science, Cornell University, Ithaca, NY, b PRODAIRY, Department of Animal Science, Cornell University, Ithaca, NY, cDepartment of Animal Science, Cornell University, Ithaca, NY, dSoil and Crop Sciences Section of the School of Integrative Plant Science, Cornell University, Ithaca, NY, eUSDA-ARS Beltsville Agricultural Research Center, Beltsville, MD, fAdvanced Agricultural Systems, LLC, Kinderhook, NY
Introduction
Forage double-cropping, or growing two forage crops in a single growing season, can be a beneficial practice for dairy farmers in New York. Double-cropping corn silage with forage winter cereals, such as triticale, cereal rye, or winter wheat, can add additional spring yield on top of numerous environmental benefits including preventing soil erosion, nutrient recycling, and increased soil organic matter over time – which all promote increased soil health. Winter cereals intended for forage harvest require nitrogen (N) management to reach optimum yield and forage quality. This study was aimed at identifying field and management characteristics that can estimate yield and N needs for winter cereals harvested for forage in the spring.
Field Research
A state-wide study with 62 on-farm trials investigated the spring N needs of forage winter cereals across New York from 2013 to 2016. Each trial had five rates of N (0, 30, 60, 90, and 120 lbs N/acre) applied to farmer-managed forage triticale, cereal rye, or winter wheat at green-up in the spring to determine the most economic rate of N (MERN). All forages were harvested at the flag-leaf stage in May each year. Soil samples were taken at green-up before fertilizer was applied. Farmers supplied information about management practices and field characteristics, such as past manure applications, planting date, and soil drainage. This information, in addition to soil fertility analysis results, was used to develop a decision tree model for predicting MERN classification.
Results
About one-third of the trials did not require additional N (MERN = 0), while the remainder responded to N and most required between 60 and 90 lbs N/acre (Figure 1). Yields at the MERN across trials ranged from 0.4 to 3.0 tons DM/acre (1.8 tons DM/acre average). Yield could not be accurately predicted based on information gathered, but the lower-yielding sites (< 1.0 tons of DM/acre) tended to be poorly or somewhat poorly drained and not have a recent manure history.
Farmer-reported soil drainage, manure history, and planting date were the most important predictors of the MERN (Figure 2). Most of the winter cereals grown on fields that were described as well-drained by the farmers did not require additional N at green-up. For the fields reported as somewhat poorly- or poorly-drained, 60 to 90 lbs N/acre were required if the field had not received manure the previous fall. If manure had been applied recently, 60 to 90 lbs N/acre were required for stands that were planted after October 1 versus 0 lbs N/acre if planting had taken place before October 1.
Figure 1. Forage winter cereal most economic rates of N (MERN) and yield at the MERN for 62 N-rate trials in New York from 2013 to 2016. Fertilizer N was applied at spring green-up and forage was harvested at the flag-leaf stag in May.Figure 2. Decision tree for forage winter cereal most economic rate of N (MERN) at spring green-up. If the indicated site or history factor in the blue box is true, move to the left branch in the tree; if false, move to the right branch. The predicted MERN is listed in the red boxes. Recent manure history refers to manure applied within the last year (either spring or fall). This decision tree correctly predicted MERN classifications for 78% of the trials included.Figure 3. Forage winter cereal crude protein as impacted by N rate applied at spring green-up for 62 trials in New York from 2013 to 2016. Forage was harvested at the flag-leaf stage in May.
Most forage quality parameters were not impacted by N rate. Neutral detergent fiber (NDF) at the MERN ranged from 42 to 60% of DM (52% average), in vitro true digestibility (IVTD) at the MERN ranged from 81 to 94% of DM (88% average), and NDFD digestibility (48-hour fermentation) at the MERN ranged from 67 to 84% of NDF (78% average). However, crude protein (CP) increased with N rate for most trials, even those with MERNs of 0. Crude protein averaged 13% of DM for the 0 lbs N/acre treatment and 20% of DM for the 120 lbs N/acre treatment (Figure 3). On average, CP increases by 1% for every 15-20 lbs of N applied. These findings suggest that additional N beyond the MERN can increase the CP levels of the forage while not impacting other forage quality parameters.
Conclusions and Implications
Results from this study emphasize the importance of growing conditions for optimum forage winter cereal performance. In fields that have poor drainage and lack recent manure histories, forage winter-cereals may not yield well and will likely require additional N inputs, while fields with well-drained soil conditions and better soil fertility will support higher yields and better forage quality without needing additional N in the spring. Planting date is also a critical management consideration. Planting late in the fall (after October 1 in this study), may result in lower yields (see also Lyons et al., 2018a). Timely planting (before October 1) in fields with good soil fertility and/or recent manure histories more often resulted in MERNs for N at green-up of 0 lbs N/acre, which would save farmers time and costs in the spring. Nitrogen management at green-up did not greatly affect forage quality except for CP, which increased with N addition even if the additional N did not increase spring yield.
Additional Resources
Lyons, S.E., Q.M. Ketterings, G.S. Godwin, J.H. Cherney, K.J. Czymmek, and T. Kilcer. 2018a. Spring N management is important for triticale forage performance regardless of fall management. What’s Cropping Up? 28(2): 34-35.
Lyons, S.E., Q.M. Ketterings, G.S. Godwin, K.J. Czymmek, S.N. Swink, and T. Kilcer. 2018b. Soil nitrate at harvest of forage winter cereals is related to yield and nitrogen application at green-up. What’s Cropping Up? 28(2): 32-33.
Acknowledgements
This work was supported by Federal Formula Funds, and grants from the Northern New York Agricultural Development Program (NNYADP), the USDA-NRCS, and Northeast Sustainable Agriculture Research and Education (NESARE). We would also like to thank participatory farmers and farm advisors for assisting with the trials, including Cornell Cooperative Extension educators, consultants, NRCS staff, and SWCD staff. 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/.
Sarah E. Lyonsa, Quirine M. Ketteringsa, Greg Godwina, Debbie J. Cherneyb, Jerome H. Cherneyc, John J. Meisingerd, and Tom F. Kilcere
a Nutrient Management Spear Program, Department of Animal Science, Cornell University, Ithaca, NY, b Department of Animal Science, Cornell University, Ithaca, NY, c Soil and Crop Sciences Section of the School of Integrative Plant Science, Cornell University, Ithaca, NY, d USDA-ARS Beltsville Agricultural Research Center, Beltsville, MD, and e Advanced Agricultural Systems, LLC, Kinderhook, NY
Introduction
Forage sorghum is a drought and heat tolerant warm-season grass that can be used for silage on dairy farms. It can be a good alternative to corn silage in New York particularly during drought years or in the case of delayed planting in the spring. Forage sorghum requires soil temperatures of at least 60°F for planting, which normally occurs in early June in New York. Forage sorghum could also be a good fit for double cropping rotations because its later planting date gives time for an early May harvest of a forage winter cereal. Between 2013 and 2017, we conducted 13 N-rate trials across three regions of New York to evaluate nitrogen (N) needs for a brown midrib (BMR) forage sorghum variety (Alta Seeds AF7102).
Trial Set-Up
The trials were planted between early June and early July in central New York (eight trials) and northern New York (five trials). Of the northern New York trials, three were on commercial farms. The other trials were on Cornell research farms. Two of the three trials on commercial farms were conducted on fields with recent manure or legume histories. For eleven of the trials, sorghum was planted at a 1-inch seeding depth and 15-inch row spacing (15 lbs/acre seeding rate). The remaining two trials were planted either with a 30-inch or 7.5-inch row spacing. Five N-rates as Agrotain®-treated urea (Koch Agronomic Services, LLC, Wichita, KS) were broadcasted at planting (0, 50, 100, 150, and 200 lbs N/acre) with two additional N rates (250 and 300 lbs N/acre) for one of the central New York locations. The forage sorghum was harvested at the soft dough stage, which occurred between September 20 and October 14. Harvest was done using a 4-inch cutting height and dry matter (DM) yield was measured. This allowed for determination of the most economic rate of N (MERN), the N use efficiency (NUE), and the apparent N recovery (ANR). The NUE and ANR are measures of N efficiency. The NUE is the amount of N taken up in relation to yield, and is calculated by subtracting the yield when no N was applied in the spring from the yield when N was applied, and dividing that value by the N rate applied (NUE [lbs DM/lbs N] = [Triticale yieldN rate – Triticale yield0 N]/N rate). A higher NUE means that more of the N that was applied was taken up by the sorghum. The ANR is the amount of fertilizer N recovered, calculated by subtracting the N in the forage when no N was applied from the N in the forage when N was applied, and dividing that value by the N rate applied (ANR [%] = [Forage N of Nrate – Forage N of N0]/N rate).
Results
The crop yield response to N could be separated into three yield response groups: (1) no response to N addition (MERN = 0; two trials), (2) no yield plateau (MERN > 200 kg N ha-1; four trials), and (3) a yield plateau between the lowest and highest N rates (seven trials) (Figure 1). The two trials on fields at commercial farms with a recent manure or legume history did not respond to N addition (group 1 trials, panel A). The trial in group 1 with the lowest yield (5.3 tons DM/ac) was planted with a 30-inch row spacing, which resulted in weed issues that likely impacted crop performance. Trials in group 2 (panel B) were either very responsive to N addition or had N uptake limitations, most likely reflecting weather or soil drainage issues. The trials in group 3 (panel C) had MERNs ranging from 134 to 234 lbs N/acre, averaging 181 lbs N/acre. Yields at the MERN for group 3 trials ranged from 6.7 to 10.4 tons DM/acre and averaged 8.9 tons DM/acre. On average, for responsive sites (so excluding group 1 trials), forage sorghum required approximately 20 lbs N/acre per ton DM. On average, for each ton of DM, 25 lbs of N was taken up by the sorghum. For group 3, higher N rates led to lower ANR and NUE (Figure 2). For these trials, NUE at the MERN averaged 56 lbs DM/lbs N and ANR at the MERN averaged 83%.
Figure 1: Impact of N application on forage sorghum yield for 13 trials from 2013 to 2017. Sorghum was harvested at the soft dough stage. Two trials did not respond to N (A), four trials did not have a yield plateau (B), and seven trials had a yield plateau between the lowest and highest N rates (C). Differences are likely due to sites native N supply, weather conditions, agronomic practices, and/or soil properties (see text for further details). Different symbols represent different sites within each group.Figure 2: Forage sorghum nitrogen use efficiency (NUE, A) and apparent N recovery (ANR, B) as impacted by N application rate for seven trials with a most economic rate of N between the highest and lowest N rates. Different shapes represent different trials within each group.
Conclusions and Implications
Forage sorghum can be a good alternative to corn silage in years of drought, delayed corn planting, or as part of a double crop rotation with forage winter cereals. The BMR forage sorghum in this study, grown on N-limited sites, needed around 180 lbs N/acre, or around 20 lbs N per ton of DM, and yielded between 7 and 10 tons DM per acre. Fields with recent manure or legume histories supplied sufficient N, resulting in no crop response to additional N for the forage sorghum. Applying N beyond the N needs of the crop will result in reduced N use efficiencies. In addition, stands with row spacing greater than the recommended 15 inches may result in weed or other stand issues that could impact performance.
Acknowledgements
This work was supported by Federal Formula Funds, and grants from the Northern New York Agricultural Development Program (NNYADP), New York Farm Viability Institute (NYFVI), and Northeast Sustainable Agriculture Research and Education (NESARE). 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 Ketterings1, Karl Czymmek1,2, Sanjay Gami1, Mike Reuter3 Cornell University Nutrient Management Spear Program1, PRODAIRY2, and Dairy One3
Introduction
The corn stalk nitrate test (CSNT) is an end-of-season evaluation tool for N management for 2nd or higher year corn fields that allows for identification of situations where more N was available during the growing season than the crop needed. Where CSNT results exceed 3000 ppm for two or more years, it is highly likely that N management changes can be made without impacting yield.
Findings 2010-2018
The summary of CSNT results for the past nine years is shown in Table 1. For 2018, 54% of all tested fields had CSNTs greater than 2000 ppm, while 44% were over 3000 ppm and 26% exceeded 5000 ppm. In contrast, 15% of the 2017 samples were low in CSNT-N. The percentage of samples testing excessive in CSNT-N was most correlated with the precipitation in May-June with droughts in those months translating to a greater percentage of fields testing excessive. As crop history, manure history, other N inputs, soil type, and growing conditions all impact CSNT results, conclusions about future N management should take into account the events of the growing season. In addition, weed pressure, disease pressure, lack of moisture in the root zone in drought years, lack of oxygen in the root zone due to excessive rain, and other stress factors can impact the N status of the crop.
Within-field spatial variability can be considerable in New York, requiring (1) high density sampling (equivalent of 1 stalk per acre at a minimum) for accurate assessment of whole fields, or (2) targeted sampling based on yield zones, elevations, or soil management units. The 2018 expansion of adaptive management options for nutrient management now includes targeted CSNT sampling. Work is ongoing to evaluate use of yield to CSNT-N ratios to identify situations where yield was limited by factors other than N supply. Two years of CSNT data are recommended before making any management changes unless CSNT’s exceed 5000 ppm (in which case one year of data is sufficient).
Figure 1: In drought years (determined in this analysis by May-June rainfall below 7.5 inches; which occurred in 2012, 2016, and 2018), more samples test excessive in CSNT-N while fewer test low or marginal.
Agronomy Factsheets #31: Corn Stalk Nitrate Test (CSNT); #63: Fine-Tuning Nitrogen Management for Corn; and #72: Taking a Corn Stalk Nitrate Test Sample after Corn Silage Harvest. http://nmsp.cals.cornell.edu/guidelines/factsheets.html.
Acknowledgments
We thank the many farmers and farm consultants that sampled their fields for CSNT. 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/.
Joseph Amsili, Aaron Ristow, Márcio Nunes, Harold van Es, Robert Schidelbeck, Mike Davis Soil and Crop Sciences, Cornell University and Cornell University Agricultural Experiment Station
Take-Aways:
Corn N Calculator (CNC) N rates based on realistic yields expectations were on average 59 lbs N acre-1 higher than Adapt-N rates, but did not result in yield increases.
Adapt-N nitrogen (N) rates led to 58% (clay loam) and 68% (loamy sand) less nitrate leaching compared to CNC N rates.
Adapt-N rates resulted in savings of $29 acre-1 compared to CNC N rates.
The over-application of nitrogen (N) fertilizer leads to large environmental problems and represents a considerable financial cost to the farmer. Despite these issues, farmers tend to over-apply nitrogen due to the difficulty of predicting the economic optimum N rate and the need to ensure high yields. Static N rate tools, like Cornell’s Corn N Calculator (CNC; http://nmsp.cals.cornell.edu/software/calculators.html), are promoted widely but don’t capture the dynamic interactions between site-specific weather, soil, and management variables. Adapt-N (http://www.adapt-n.com), a dynamic-adaptive N recommendation tool, was designed to integrate real-time weather and site-specific soil and management data to predict the optimum N rate.
In previous studies, it was demonstrated that Adapt-N can produce comparable yields to static N models and grower selected rates, while reducing overall N inputs (What’s Cropping Up article on comparing static and Adaptive N Tools; What’s Cropping Up article on comparing Adapt-N and CNC Tools). Yet no field experiments had been conducted to compare the effects of Adapt-N and a static N calculator on measured nitrate leaching. This study utilized two long-term tillage experiments to measure the effects of modeled N rates (Adapt N vs. CNC), soil type (clay loam vs. sandy loam), and tillage practices (no-till vs. plow-till) on nitrate leaching.
Methods
Adapt-N and CNC nitrogen recommendations were superimposed onto two long-term tillage experiments (plow and no-till) at the Cornell Willsboro Research Farm for four years (2014-2017). The trials were done on contrasting soil types, one on a Muskellunge clay loam and the other on a Cosad loamy fine sand. Nitrogen rates included 15 lbs N/acre as starter fertilizer and the rest was side-dressed approximately six weeks after planting. CNC N rates were calculated using accurate yield potentials for each plot at the two sites (default yield potentials in the tool are unrealistically low). Adapt-N recommendations were developed considering plot-specific soil textures, organic matter contents, rooting depths, crop rotations, tillage practice, crop cultivar and population, previous N applications, drainage, and yield potentials, as well as daily weather information and grain and fertilizer prices.
Corn silage yield was collected each year by hand harvesting two 5 m corn rows at three locations per plot. Drainage water samples were collected on 14 dates between April 2015 and October 2017 (Figure 1) on dates when the drain lines discharged. Water samples were analyzed for nitrate, NO3–, and nitrate, NO2–, which we simply refer to as nitrate in this article because the nitrite fraction is generally less than 1%.
Results and Discussion
Nitrogen rates and Yield
The CNC tool calculated 59 lbs acre-1 higher average N application rates than Adapt N (186 vs. 127 lbs N acre-1; Table 1). There were only two instances (both wet seasons on the clay loam soil) where Adapt-N predicted higher N rates than the CNC tool.
Soil type had a very strong effect on corn silage yield, which were 2.37 tons acre-1 higher in the loamy sand plots than the clay loam plots. Despite a lower yield potential for the clay loam site, the mean recommended N rate for that soil was 17 lbs acre-1 higher than the loamy sand site. This indicates that both N tools assume a lower nitrogen use efficiency (NUE) for finer textured soils.
While CNC N rates were much higher than Adapt N rates, they did not result in increases in yield (16.28 vs. 16.30 tons acre-1; Table 1). We found no relationship between N rate and yield as equally high yields were achievable at 100 lbs N acre-1 with Adapt-N as with CNC rates higher than 180 lbs N acre-1 (Figure 1). The Adapt-N rates resulted in calculated savings of $29 acre-1 (based on a fertilizer price of $0.50 lb N-1) compared to the CNC N rates since yields between the N tools were indistinguishable.
Nitrate Leaching
Soil type and N Tool were important drivers of nitrate leaching in this study. Nitrate leaching averaged two times higher in sandy loam soils than clay loam soils (16.47 vs. 8.34 mg NO3–+NO2– L-1; Table 1) despite slightly higher N rates for the clay loam soils. This “missing” nitrogen in leached waters under the clay loam soils suggests that denitrification is an important N loss pathway in these finer textured soils, which is a well-documented phenomenon.
In addition to higher fertilizer costs per acre, CNC N rates led to 58% higher nitrate leaching in clay loam soils (10.32 vs. 6.55 mg NO3–+NO2– L-1) and 68% higher nitrate leaching in loamy sand soils (20.69 vs. 12.29 mg NO3–+NO2– L-1) compared to Adapt-N (Table 1). Increases in nitrate leaching were proportionally larger than the increases in N rates (46 % higher for CNC than Adapt N for clay loam; 43% higher for loamy sand). This pattern indicates that N rates above the optimum have disproportionately large environmental impacts. Also, average nitrate concentrations in leached water under CNC plots exceeded the U.S. EPA drinking water standard of 10 mg NO3– L-1 for both soil types. But nitrate concentrations under Adapt-N plots only exceeded the EPA standard at the loamy sand site.
Despite high variability in nitrate concentrations at different sampling dates, there was a positive relationship between N rate and nitrate concentrations in leached water (Figure 1). The exponential relationship suggests that nitrate leaching is more sensitive to increasing N rates on loamy sand soils than clay loam soils (Figure 1). We noticed that extremely high nitrate concentrations (> 50 mg NO3–+NO2– L-1) in leached water in loamy sands occurred after long dry periods (e.g., in the 2016 growing season) under CNC N rates, but not Adapt-N rates.
Tillage effects were modestly significant and on average the mean nitrate concentrations were 45% higher for the plow than no-till in the clay loam and 5% higher in the loamy sand.
Conclusions
This study compared the static Corn N Calculator and Adapt-N and showed that the CNC seriously over-predicts the optimum N rate when based on realistic corn yields because the higher N rates did not result in yield benefits. Use of Adapt-N led to savings of $29 acre-1, reduced nitrate leaching by between 58% (clay loam) and 68% (loamy sand), and helped keep nitrate concentrations in drain water below or near the U.S. EPA drinking water standard.
Acknowledgements:
Research was funded by the Northern New York Agricultural Development Program, USDA-NRCS, and New York Farm Viability Institute.
