Protein Mapping Identifies Nitrogen Limited Zones Within the Field

By CropLife

Water and nitrogen are the two major drivers of yield within cereal crops, writes Phillip Clancy at CropLife. Insufficient nitrogen availability and uptake by plants throughout the growing cycle will limit the yield of the crop. Accurately identifying the zones within a field where yield has been limited by the nitrogen availability, has been the objective of precision agriculture for more than 30 years.

Many technologies have been developed to measure the nitrogen content and distribution in soils across the field, as well as measuring the effect of water and nitrogen on the biomass production. These technologies have several limitations in that they do not reliably identify nitrogen limited zones. Now there is a new technology that measures the nitrogen in the seeds in the form of protein. An on-combine NIR analyser measures protein, moisture, oil, and starch in real time as grains are harvested. By combining protein and yield along with GPS coordinates, a new field map — Protein/Yield Correlation Quadrant Map — is generated that identifies zones where the protein is low, and the yield is low. These zones are where the application of more nitrogen fertilizer will produce a Positive Yield Response.

This article describes the three technologies that are available for farmers to measure nitrogen in the soil and discusses the application for each technology and the potential benefit offered to farmers.

Measuring Nitrogen

There are many scientific reports that demonstrate the relationship between nitrogen and yield in cereal crops, (i.e., wheat, barley, and corn). Nitrogen is required as the seeds sprout and emerge through the soil. If there is not enough nitrogen, then the plant may not develop the full number of tillers which then sets up the yield potential for the crop. During the stem elongation and leaf development stages, nitrogen is required in photosynthesis to produce the sugars and proteins that eventually make up the plant. Insufficient nitrogen during the biomass production stages will limit the size of the plant and the yield of the fruit that it will produce.