New Technologies to Reduce Barriers to Implementation of Nutrient Loss Reduction Strategies
Issue
A major barrier to the implementation of nutrient loss reduction strategies is cost. Farmers do not want to lose nutrients. New technologies that reduce nutrient losses and improve profitability can increase implementation. Nitrogen fertilizer management is one tool that can reduce loss and improve profitability. Use of the ‘Late Spring Nitrate’ soil test to guide nitrogen fertilizer applications can achieve a 30 percent load reduction at watershed scale. However, implementation of this test is low, likely due to several reasons — effectiveness of the test is poor when fertilizer is applied in concentrated bands as is common practice; there is significant delay between sampling and receipt of test results; and the test is expensive due to labor requirements for sampling.
Objective
This project will calibrate and validate a new “Corn Stalk Nitrate Test” for sidedress N fertilizer, and calibrate and validate a new “Late Spring Sulfate Test” for sidedress S and N fertilizer.
Approach
The new Corn Stalk Nitrate Test will be made with conventional chemistry methods and new sensors. Researchers will work with 10 independent farmers, who will receive and use the new sensors. The new sensor, a needle inserted into the corn stalk, provides a reading in less than 10 seconds to a smartphone app. In addition, the new Late Spring Sulfate Test is a soil-based test the team will add to the Late Spring Nitrate Test (LSNT). The LSNT is a soil test made at corn growth stage V6 to recommend sidedress. Each farm will include small-scale replicated research plots with seven N fertilizer rates, and large-scale, replicated N rate strip trials including at least three sidedress N fertilizer rates. The small-scale plots will be used to calibrate the new tests. The large-scale strips will allow farmers to make management decisions based on sensor-measurements they take themselves and demonstrate the effectiveness of the test-recommendations.
Project Updates
Note: Project reports published on the INRC website are often revised from researchers' original reports to increase consistency.
October 2022
FINAL REPORT
Key Research Questions
Can spring corn stalk nitrate concentration predict nitrogen fertilizer demand and the need for sidedress nitrogen fertilizer application? In-season nitrogen fertilizer application can reduce nitrate losses to waterways and increase fertilizer use efficiency. At present, the late-spring nitrate test helps farmers to determine if corn will benefit from a sidedress nitrogen fertilizer application. Soil is sampled around the fourth to sixth-leaf growth stage and the concentration correlates with the probability that additional nitrogen fertilizer will benefit yield. However, the increasing frequency of highly concentrated fertilizer application in narrow bands of soil and the labor and slow laboratory turn-around time of soil sample analysis hamper the adoption of the soil test to help guide fertilizer applications. Our goal was to develop a similar test based on corn stalk nitrate concentration that has lower cost and labor requirements.
Research Findings
We sampled eight nitrogen fertilizer rate trials to corn around the state of Iowa. Our results showed a correlation between stalk nitrate and the probability that more nitrogen fertilizer would be economical. The predictive ability of stalk nitrate concentrations was superior to canopy sensing but slightly less predictive than the standard late spring soil nitrate test approach. However, in contrast to our limited data set, the late spring nitrate test benefits from decades of research including hundreds of site-years of data. Because the corn stalk nitrate test performed nearly as well despite a very limited sample size suggests there is potential to improve corn stalk nitrate testing in the future.
Project Activities
- 4 presentations
- 2 field days
Publications
Understanding and predicting nitrogen dynamics in the Midwest United States Corn Belt. NK Mahal. PhD Dissertation, Iowa State University.
Journal Articles Submitted
Chen, Y., Tang, Z., Zhu, Y., Castellano, M. J., & Dong, L. (2021). Miniature multi-ion sensor integrated with artificial neural network. IEEE Sensors Journal, 21(22), 25606-25615.
December 2019
We aim to develop a new plant test to determine nitrogen fertilizer requirements for corn. The test will use the corn stalk nitrate concentration at the vegetative growth stage nine to predict nitrogen fertilizer requirement. At present, the late spring soil nitrate test is used for this purpose. However, banded N fertilizer applications and the labor of soil sampling make this an unattractive test to many farmers.
During this project period, we initiated six field experiments where we compared the late spring nitrate test and the corn stalk nitrate concentration. At each location, different N fertilizer rates were applied. At the end of the season, researchers will determine if there is a relationship between corn stalk nitrate concentration, soil nitrate concentration and percent maximum yield.
Outreach during this period included 1 field day and 1 presentation
July 2019
This research aims to develop a new plant test to determine nitrogen fertilizer requirement for corn. The test will use the corn stalk nitrate concentration at the vegetative growth stage nine to predict nitrogen fertilizer requirement. At present, the late spring soil nitrate test is used for this purpose. However, banded N fertilizer applications and the labor of soil sampling make this an unattractive test to many farmers.
In addition, researchers aim to deploy a new sensor that can make the corn stalk nitrate measurement instantaneously, in the field. During this project period, six field experiments were initiated to compare the late spring nitrate test and corn stalk nitrate concentrations. At each location, different N fertilizer rates were applied. At the end of the season, the research will determine if there is a relationship between corn stalk nitrate concentration, soil nitrate concentration and percent maximum yield.
December 2018
Spring 2019 will be the first field research season for this project. In preparation for the spring, researchers met with the Iowa Soybean Association to coordinate on-farm research locations. Candidate farmer-cooperators have been identified and sites are being selected. Everything is on schedule.