Quirine Ketterings1, Karl Czymmek1,2, Sanjay Gami1, Mike Reuter3 Cornell University Nutrient Management Spear Program1, PRO-DAIRY2, 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. Research shows that the crop had more N than needed when CSNT results exceed 2000 pm. Results can vary from year to year but 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 ten years is shown in Table 1. For 2019, 33% of all tested fields had CSNT-N greater than 2000 ppm, while 24% were over 3000 ppm and 11% exceeded 5000 ppm. In contrast, 31% of the 2019 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. This includes 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 that 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 as a result of findings that targeted sampling generates more meaningful information while reducing the time and labor investment into sampling. 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/.
Jerry Cherney and Bill Cox, Soil and Crop Sciences Section, Cornell University
Research has been conducted on a range of corn silage management topics in NYS over the past few decades. This summary is based on research that has included multiple sites and/or multiple years. Issues can be divided into two basic categories: Concerns prior to planting and concerns after planting. First, we prepare for the season, and then we have a limited number of options to react to the specific weather conditions of each season.
Pre-season
Hybrid selection While there are a number of options regarding plant genetics, of primary concern is the selection of the correct maturity group for your area and for the particular season (Fig. 1). You can expect to increase yield by about one ton/acre for every 10 additional maturity group days. The greater the maturity group, the higher the moisture content will be on any given fall date. Keep in mind that moisture loss per day keeps shrinking through the fall period (Fig. 2), making it increasingly difficult to reach optimum moisture in late fall.
Fig. 1. Effect of Maturity group selection on moisture and yield of corn silage, assuming all are harvested on the same day.Fig. 2. Approximate moisture loss per day through the fall.
Maturity group selection is influenced by your planting date and by your normal first frost date. 1) Plant full season hybrids from late April (if soil is dry) to late May, 2) Adjust hybrid relative maturity to planting date – mid-season hybrid from late May-~June 10, or 3) Plant early-season hybrids after June 10.
Brown-midrib (BMR) corn hybrids continue to improve in comparison to other options, and are worth considering. BMR hybrids will yield about 90% of a normal hybrid, plus or minus a few percent. On the plus side, BMR hybrids can be up to 25% higher in fiber digestibility (NDFD) than normal hybrids. Dairy feeding trials have shown that a small increase in ration fiber digestibility produces a significant increase in milk production.
While there still may be some increased potential for lodging, current BMR hybrids are much improved over the original BMR offerings. However, one issue that remains is dry down, BMR hybrids tend to retain moisture significantly longer than normal hybrids in the same maturity group. Also, there are indications that BMR types are somewhat lower in starch digestibility than floury types.
Seeding rate Numerous seeding rate trials over several decades in NY produced relatively consistent results (Fig. 3). Soil type has some impact on suggested seeding rates. Deep, well-drained soils => 36,000; Moist silt loam soils => 34,000, and Droughty soils => 30,000. Seeding at a rate of 35,000 is now very common in NY.
Fig. 3. Yield as influenced by plant density.
Row spacing Trials comparing narrow rows (15”) with standard 30” rows have shown increased yield with narrow rows, if fertilized adequately with N (Fig. 4). Narrow rows have a more equidistant plant spacing, resulting in full sunlight being intercepted earlier in the season. The possible downside to narrow rows includes purchase of a new planter, and a row-independent harvesting head if not already on-hand. Any post-emergence applications will result in some wheel traffic damage, which can be minimized by large-width application equipment. Partial budget analysis, assuming the purchase of new equipment, shows a significant increase in returns when converting to narrow row corn.
Fig. 4. Narrow rows can increase yield, if adequately fertilized.
During the Season
Side-dress N There is an optimum amount of N for a given field that will maximize yield, excess N application beyond the optimum amount will have negative environmental consequences. There are several alternative methods for determining side-dress N application to corn, and also methods for evaluating the relative success of the chosen application rates.
Whatever method is used to determine N application rates, it is critical to have confidence in that process, as it must adhere to federal conservation practice standards, which are mandatory for concentrated animal feeding operations (CAFOs). The process for development of Land Grant University guidelines for fertility management and for evaluating environment risk is currently being formulated.
Harvest stubble height If excess silage yield is anticipated, corn may be harvested at a higher stubble height to increase silage quality. Yield decreases linearly and NDFD increases linearly, with increased harvest stubble height (Fig. 5). A corn plant is basically a low-quality fiber pole that holds a high-quality grain bin. Cutting the plant higher up loses some fiber (lower yield), but it concentrates the impact of the grain bin (higher quality). Conversely, cutting perennial grasses or legumes high to improve quality ends in failure, it only reduces yield.
Fig. 5. Relationship between harvest stubble height of corn silage and yield or quality.
If you are routinely cutting high to increase corn silage quality, consider switching to BMR hybrids. The typical yield loss with BMR is in the same range as the yield loss due to high stubble height. The increase in fiber digestibility with BMR, however, can be three times as great as the NDFD increase due to high stubble height.
Determining optimum moisture at harvest Harvesting at optimum moisture content is more important than hybrid genetics selection. Optimum moisture content for making silage is between 60 and 70%, although generally the ideal moisture content is in the upper 60’s. It is nearly impossible to estimate whole plant moisture content visually. There are several methods of estimating moisture content to optimize moisture at harvest.
It is very difficult to estimate whole plant moisture visually.
Growing Degree Days. On average, a 100-day hybrid will have 1200 GDD from planting to silking. Another 800 GDD is the average from silking to silage harvest. The current year’s local weather data can be used to determine the actual GDD up to the present time, and then long-term average weather data can be used to predict into the future. The shorter the prediction time period, the more accurate a GDD prediction will be.
Chop and measure moisture. A more accurate method of determining whole plant moisture is to use the harvester to chop a few hundred feet into the field and either dry a sample or use an on-board NIRS instrument to determine moisture content. While this can be very accurate, it only provides a measure of moisture for the current day. An estimate of future field drying is required (Fig. 2) to reach optimum moisture.
Cut a sample by hand. Another method is to walk through a portion of the field and cut a number of plants by hand, then chopping the plants and drying to determine moisture content. The number of plants required depends in part on the uniformity of the field. During the fall of 2019 we cut 40-50 individual plants/field out of a number of fields across central and northern NY. Since we measured individual plant moisture content, it was possible to determine the number of plants required to get a representative field moisture value. For a very uniform field, 5 plants are likely to provide a good field moisture estimate. Even with more variable fields (uneven emergence issues, etc.) 10 plants is likely to provide a reasonable estimate of field moisture.
NIRS on whole plant corn. Since estimating moisture content for harvest is critical, we are evaluating small hand-held NIR units to determine if it is possible to estimate standing whole plant corn moisture. One major issue with standing whole plants is that ear moisture changes at a very different rate than stover moisture. Ears begin drying down much earlier than the stalk, so estimates of standing plant moisture may need to include information on both ear and stover moisture status. A fast and accurate method of estimating field moisture would be very beneficial for the large acreage of corn silage in NY.
There are many important management decisions regarding corn silage that must be made prior to the start of the season. The relatively few management decisions that can be made during the growing season, particularly moisture content at harvest, can make the difference between profit and loss.
Karl J. Czymmek1,2, Quirine M. Ketterings2, Mart Ros2, Sebastian Cela2, Steve Crittenden2, Dale Gates3, Todd Walter4, Sara Latessa5, and Greg Albrecht6
1PRODAIRY, 2Nutrient Management Spear Program (NMSP), Department of Animal Science, Cornell University, 3United States Department of Agriculture Natural Resources Conservation Service (USDA-NRCS), 4Department of Biological and Environmental Engineering, Cornell University, 5New York State Department of Environmental Conservation (NYSDEC), 6New York State Department of Agriculture and Markets (NYSDAM)
After more than 15 years of field use, version 1 of the New York Phosphorus Index (NY-PI) has been updated. The new version (NY-PI 2.0) incorporates new science and does a better job of addressing P loss risk while still giving farm managers options for recycling manure nutrients. The process of updating the NY-PI was led by the NMSP at Cornell in partnership with NYSDAM, NYSDEC, and NRCS and in consultation with certified planners and farmers. Farms that are regulated as concentrated animal feeding operations (CAFOs) will need to start using the new NY-PI when the CAFO Permit is updated (current permits are due to be renewed in 2022). Farms that are in state or federal cost share programs will need to use the tool based on NRCS determination. Agency discussions are in progress to make sure the roll-out is as smooth as possible.
Figure 1: the new NY-PI has a transport × BMP approach.
Here is how it works: a farm field is rated based on an assessment of its runoff risk-related transport features, including those observed directly during a field visit and others from normal soil survey information (most of these factors are the same as those used in the old NY-PI). For example, being close to a stream or watercourse, poorly drained soil, or higher levels of soil erosion are some of the risk factors that can lead to a high transport score. For fields with a high transport score, manure and P fertilizer application practices can be selected to reduce the transport risk. These best/beneficial management practices (BMPs) cover a combination of changes in application timing (close to planting) and method (placing P below the soil surface), and more vegetation on the soil surface when P is applied. Thus, implementation of BMPs will reduce the final PI score. Field practices include setbacks, ground cover (sod or cover crops) or placing manure below the soil surface (injection or incorporation). Combined with information about soil test P levels, the final NY-PI score results in a management implication: if risk is classified as low or medium, manure may be used at N-based rates; if classified as high, manure rate is limited to expected P uptake by the crop, and if very high, no P from manure or fertilizer may be applied. This transport × BMP approach is shown in Figure 1.
Coefficients were set for the new NY-PI using a database of more than 33,000 New York farm fields supplied by certified nutrient management planners and a second dataset that included data for PI assessment and whole-farm nutrient P balance assessments for 18 New York AFO and CAFO farms. While some farm fields had to have manure diverted, in almost all situations, the NY-PI 2.0 provided a pathway for farms with an adequate land base to both reduce risk and apply the manure generated from their herd. The full NY-PI 2.0 can be seen in Table 1.
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 as a result of findings that targeted sampling generates more meaningful information while reducing the time and labor investment into sampling. 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).
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/.
