Testing techniques after corn crop removal for fertilizer application

Jacob Sharkey

This project will investigate the different techniques which test for nitrates following the removal of a corn crop. Each of the techniques will sample at depths of 0-6”, 6-24”, and 24-48”. After analyzing the results, we will then be able to determine which technique is best to use for fertilization of corn, sugar beets, or another specialty crop that requires nitrate management following the harvest of a corn crop.
The purpose is to investigate the results of each technique and how the results differ on a set number of acres. The techniques being used for the study will be sampling the field according to 20-acre strips, 4.4 acre grids, and Zone sampling using productivity zones made by Veris Cart/EM38 sensor. All the nitrate sampling will be done Fall of 2019.
First, the field will be tested on 20-acre strips. 8-12 samples will be collected randomly throughout the 20 acre blocks using a composite sample technique with no geographically referenced sample points. Secondly, the field will be tested off of 4.4 acre grids. Using this technique, a sample will be collected every 4.4 acres using geographically referenced points; thus, a sample result will be tied to an area 4.4 acres in size throughout the entire field. Lastly, using a Veris Cart/EM38 Sensor we will determine productivity zones throughout the field to sample from. Using these zones, 8-12 geographically referenced points will be placed within each zone to take a sample at. As a result, one soil sample will be collected per zone.
In summary, once all results are analyzed, we will then determine which technique is the best for sampling for nitrates to improve the productivity and profitability for nitrate management on a piece of land. Being able to side by side compare whole field results from each technique will be a nice way of showing how each result may differ between the techniques used for the sample. Being provided this information could lead to the application of less nitrogen on less productive ground where crop removal is minimal and the application of more nitrogen on more productive soil where crop removal is greater. This may result in less inputs and higher ROI without over applying fertilizer and gaining maximum yields. By comparing the results from the different techniques, it will reveal nitrate trends throughout a given field and guide us in a way to nitrate model more efficiently and accurately in the future.