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.
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.