With the continuing rise in crop input costs farm mangers are interested in tools that allow them to properly credit the nutrients they have on the farm (manure, compost, cover crops, plant residues from crop rotations, etc.) and minimizing purchased fertilizer. The Illinois Soil Nitrogen test (ISNT) and corn stalk nitrate test (CSNT) are two management tools that can be used to illustrate where adjustments to N management for corn can be made, using an adaptive management approach with farmers as decision makers. While a growing number of farm managers see the value of the CSNT and ISNT information, feedback showed the need to find (1) more efficient and lower cost methods to gather the samples and run the tests, and (2) a more straightforward process to interpret the results.
This project addressed three practicality questions raised by farmers: (1) can CSNT samples be collected after harvest rather than walking through standing corn (time reduction); (2) can certain fields be targeted or should the whole farm be sampled; and (3) what is the cost of sample collection and testing compared to the benefits of reduced N fertilizer.
For the two farms in the project, all corn fields were sampled in fall 2011 with followup sampling for fields that remained in corn in fall 2012. Based on feedback from the two farmers and their advisors and other farm teams with experience with the test, and based on an evaluation of the impact of sampling protocol on CSNT values, a new protocol was developed and introduced at the 2012 NRCCA training held at the end of November, 2012, and attended by 73 certified crop advisors.
The new protocol is documented in Agronomy Factsheet 72 (“Taking a Corn Stalk Nitrate Test Sample After Corn Silage Harvest”, 11/21/2012) downloadable from our NMSP website: http://nmsp.cals.cornell.edu/publications/factsheets/factsheet72.pdf). Additional factsheets were developed featuring the adaptive management approach, on-farm research, and fine-tuning N management with the combined use of ISNT and CSNT (http://nmsp.cals.cornell.edu/guidelines/factsheets.html). Both farms considered whole farm CSNT sampling most useful for making management decisions, but would consider taking a subset of a minimum of six fields. Savings in fertilizer costs greatly depend on the distribution of CSNT levels and common practice (manure versus fertilizer use). Farm advisors (consultants) involved with the project have added the CSNT to the tools they recommend for farmer clients to evaluate N management of corn.
True to the old adage “you cannot manage what you do not measure”, data-driven decision making results in positive management changes that have measurable economic, social, and environmental impact at the farm level. This was shown by a group of 54 farms that completed whole farm nutrient mass balance (NMB) assessments for 4 years; on average, these farms achieved a 30-50% reduction in nitrogen (N), phosphorus (P), and potassium (K) use as measured by whole farm NMBs. While the NMB indicates an annual accumulation or loss of nutrients from the farm (nutrient excess or deficiency on a lb/acre or lb/cwt basis), it does not specifically identify the main drivers of the balances. As a result, farm managers made changes on a trial and error basis; we would like to make this a more directed process, and farmers have asked for guidance and tools for decision making for N fertilizer and manure use, recognizing the need to have actual verifiable data.
In recent years, two tools were evaluated, calibrated for local production conditions, and made available to farms to aid in N management decision making. The Illinois Soil Nitrogen Test (ISNT) is an organic N test that is an indicator of soil N supply potential (N expected from readily mineralizable organic matter). The Corn Stalk Nitrate Test (CSNT) allows managers to retrospectively evaluate if the corn had sufficient, insufficient, or excess N available that year (“a report card” to be used as guidance for the following year). Combining both tools allows farmers to measure, evaluate, and refine manure and fertilizer application strategies for delivering the right amount of N. In a previous project aimed at identifying nutrient management tools for small dairies, farmers identified soil testing and the CSNT as effective tools for small farms (http://nyfvi.org/default.aspx?PageID=2257&NewsID=276). Similarly, larger farms benefited from the test package.
Three main issues were identified in previous year: (1) can we make sampling for CSNT more practical (sampling after harvest rather than walking through standing corn); (2) do we need to sample the whole farm or can we target fields?); and (3) relating cost of sample collection and testing to benefits of reduced N fertilizer cost or reallocation of manure.
The Nutrient Management Spear Program CSNT database shows several farms have been assessing just one or two fields for CSNT raising questions related to transferability to other fields. Sampling more farm fields could result in a more complete whole farm N use evaluation and facilitate quicker improvements in N use efficiency (greater trust in data), reducing N losses to the environment and increasing farm profitability, but this creates an additional workload and will add to the costs.
This project, initiated by ideas from two dairy farm management teams, aims to identify a more practical and effective sampling process for the ISNT and CSNT for use by farmers and their advisors, independent of farm size.
Two local farms will work with campus staff to evaluate implementation protocols for the ISNT and the CSNT and develop a more farmer-friendly approach to assessing performance for whole farm N fertilizer and manure use decision making. Each farm team will compare targeted (some fields only) and whole farm (all fields) approaches to evaluate the effectiveness of the tool package in reducing risk of both over and under fertilization (i.e. in generating confidence that changes can be made). Each farm team together with the NMSP staff will conduct a cost/benefit analysis of different protocol approaches. The analysis will compare the cost of implementation, using both old and newly-adapted sampling and implementation strategies, to the fertilizer saving benefits realized using the information provided by the tests. The results of the three practicality studies will provide the guidance needed to develop a new sampling protocol that requires less labor but is still accurate and will allow for greater adoption by other farms.
Two farms management teams contacted the Nutrient Management Spear Program (NMSP) staff during the 2011 growing season with a keen interest in using the information provided by the ISNT and CSNT to monitor and adapt their N management strategies over time (see support letters). These two farms collaborated with Cornell’s NMSP staff to evaluate and, assuming it is feasible to make changes, revise the field sampling guidelines for the ISNT and CSNT. Based on their experience with the tests, each crop management team provided ideas and suggestions to improve practicality and feasibility of implementing the tools on their farms. Suggestions focused on how to make it easier to take samples by farm staff (and farm advisors) and to reduce the sampling time currently needed for each field.
In the fall of 2011, initial team meetings were held with the two farms to discuss current sampling guidelines for soil (http://nmsp.cals.cornell.edu/publications/factsheets/factsheet1.pdf) and CSNT (http://nmsp.cals.cornell.edu/publications/factsheets/factsheet31.pdf) and to identify possible alternative approaches to sampling for ISNT and CSNT that will deliver reliable results. An alternative method for sampling (after harvest, simultaneous sampling for CSNT and ISNT) was proposed and implemented at one of the two farms. Standard procedures were used for the other farm (high density sampling prior to harvest for CSNT and directly after harvest for ISNT…two visits). One farm continued to do all its own sampling after harvest (lifting up the chopper at locations within the fields), the second farm was sampled by the NMSP team before harvest in 2011. We worked with the farms to combine field data with sampling results, interviewed the farmers to get their feedback on results, and continued with a second round of samples in fall 2012 (fields that had remained in corn that year) with sampling after harvest. The data for 2012 were compared to the data from 2011.
Suggestions from crop management teams were incorporated into sampling protocol documents, and new factsheets were developed and posted to the Nutrient Management Spear website (http://nmsp.cals.cornell.edu). The excel spreadsheet was updated as well and samples were run for any farmer with an interest in evaluating ISNT and/or CSNTs for his or her corn fields (fee basis).
Based on feedback from consultants and farmers and earlier studies, a new CSNT sampling protocol was developed and introduced to facilitate sampling after corn silage harvest (shorter stalks) as walking through standing corn was identified as a major deterrent to sampling fields for CSNT by the farm teams and others who sampled fields for CSNT this year (923 farm field samples were analyzed for CSNT in the fall of 2012).
Sampling protocols for ISNT remained the same; CSNT sampling post harvest can more easily be combined with ISNT sampling as well, reducing the overall time investment in sampling for both. Factsheets were developed to aid producers in implementing an adaptive management approach that includes sampling 2nd or higher year corn fields for CSNT and using the ISNT to identify fields where N application rates can be reduced.
The current dataset for the two farms in this project showed the impact of the drought of 2012 on CSNT distribution (more fields excessive in CSNT). This is an important aspect of learning to use the CSNT as such higher numbers indicate excess N that year but would not necessarily imply that rates need to be reduced the following year. Drought years will occur and the CSNT data will need to be evaluated in light of the growing conditions of the year. Results of the project showed the need to further evaluate year to year and within field differences (temporal and spatial variability) in coming years.
We also worked with a commercial laboratory to thoroughly test and implement CSNT testing at the facility, consistent with the methodology used at the NMSP lab (technology transfer to allow for greater adoption by farmers in the state). This laboratory (DairyOne Forage Laboratory) will start running CSNTs for this coming harvest season, making the test available on a commercial basis to a potentially much larger audience.
Sample size increases over the past several year has shown a steady increase in the number of fields being analyzed for CSNT, from 509 in 2010, to 765 in 2011 and 923 in 2012 (samples analyzed by the NMSP). This increase took place with standard protocols in place. The biggest impact from this project has been the development and release for use of an alternative sampling and analyses protocol for CSNT (post-harvest). This is documented in a new Agronomy Factsheet: Taking CSNT samples after corn silage harvest (http://nmsp.cals.cornell.edu/publications/factsheets/factsheet72.pdf). The new protocol, first implemented in the fall of 2013, will allow for a greater number of samples to be taken as it saves time if samples can be taken using a 4-wheeler after silage harvest. A new factsheet is being developed to introduce an adaptive management process for CSNT and ISNT use for corn, while also determining corn yield. A draft of this factsheet is under review with NRCS, NYDEC, and NYSDAM as well as Cornell University, and the final version is expected to be released this fall. New approaches, consistent with the Adaptive Management approach recognized as an effective way to fine-tune management over time by NRCS, are being developed and discussed.
Education & Outreach Activities and Participation Summary
Summarizing the results of both this grant and work with farm advisors on agriculture and environmental indicators (NESARE ENE09-112) and NNYADP, ISNT and CSNT related agronomy factsheets developed and/or updated include:
# 36: Illinois Soil Nitrogen Test for Corn (1/17/2008; revised 1/12/2012)
# 63: Fine-Tuning Nitrogen Use on Corn (9/8/2011; revised 1/12/2012)
# 68: On-Farm Research (7/9/2012)
# 69: Adaptive Nutrient Management Process (7/22/2012)
# 71: Measuring Corn Silage Yield (9/15/2012)
# 72: Taking a Corn Stalk Nitrate Test Sample After Corn Silage Harvest (11/21/2012)
These can be downloaded (http://nmsp.cals.cornell.edu/guidelines/factsheets.html). We are working on factsheet 73 that spells out an adaptive management approach that requires yield measurements as well, to be released this fall.
Additional extension articles in Eastern DairyBusiness:
– Ketterings, Q.M., and K.J. Czymmek (2013). Corn as a luxury consumer of N? Really? Eastern DairyBusiness; The Manager. 5(2): 19.
– Ketterings, Q.M., and K.J. Czymmek (2012). Farm-level tools refine nitrogen management. Eastern DairyBusiness; The Manager 4(2): 26-27.
Current costs for analyzing a stalk sample for CSNT is $10-$12 (depending on the laboratory) while ISNT analyses costs $12.50-$15 per sample. Sampling a field will depend on the size of the field but typically add $15-$20 of consultant time to the costs of the analyses (ISNT and CSNT can be done at the same time). The ISNT samples do not need to be taken every year (once in three years is enough) while CSNT samples should be taken annually. Assuming a typical field size of 10 acre, the total costs for the combined ISNT and CSNT package is estimated at no more than $6 per acre per year. Savings vary depending on CSNT and ISNT distribution and manure versus fertilizer use but with N fertilizer costs at 60 cents per pound of N, a minimum savings of 10 lbs of N/acre is needed to make up for the costs of the sampling and sample analyses. For farms with a large number of fields excessive in N due to fertilizer use, the savings of implementation of the combined CSNT and ISNT package can quickly pay back the costs associated with the sampling. Cost saving measures were determined (shorter stalks, easier sampling, laboratory protocols that save time in the lab).
A growing number of farm fields is being analyzed for CSNT (923 samples in 2012 versus 105 samples in 2007 when we introduced the test for use in New York State, with a steady increase in the past two years. The list of crop consultants that have started to use the CSNT (sometimes with sometimes without use of the ISNT) is growing as well and the crop advisors for both farms in the grant are recommending the test to their clients. I fully expect the numbers of samples to grow once the DairyOne Forage Laboratory starts offering the test for this fall as well (comparison study almost completed). Adoption of the ISNT is slowly increasing but is faced with more challenges resulting from the separation of labs for this test (ISNT test offered by NMSP only, versus regular soil testing done by other laboratories). This is a challenge that will need to be addressed in future years.
Areas needing additional study
Discussions and results from the two years show that the main focus in future work needs to be on evaluation of spatial and temporal variability in both CSNT and ISNT. The CSNT and ISNT package is powerful in identifying areas of possible fertilizer savings (material and application costs) but we need to get a better sense of variability over years, and especially determine how drought or excessively wet years impact the results and interpretations of the CSNT.
- Eastern Dairybussines: Farm-Level Tools Refine Nitrogen Management
- Eastern DairyBusiness: Corn as a Luxury Consumer of N? Really?
- Factsheet 72: Taking a Corn Stalk Nitrate Test Sample After Corn Silage Harvest
- Factsheet 36: Illinois Soil Nitrogen Test for Corn
- Factsheet 63: Fine-Tuning Nitorgen Use on Corn
- Factsheet 68: On-Farm Research
- Factsheet 69: Adaptive Nutrient Management Process
- Factsheet 71: Measuring Corn Silage Yield