As we get into August, corn growers are always looking for ways to maximize their crops and to determine how effective their nitrogen management plans were with respect to their application.
This test is becoming increasingly popular each year. I really like the definition stated below from the Purdue University Department of Agronomy. It explains the basis for the test and what it measures.
The basis for the test lies in the fact that corn plants deficient for nitrogen will usually remobilize stored N from the lower portions of the stalk and leaves to the developing grain; resulting in lower stalk nitrogen concentrations at the end of the season. Plants that take up excessive amounts of soil nitrogen (more than is needed for maximum yields) will store excessive amounts in the lower stalk sections by the end of the growing season; resulting in higher stalk nitrogen concentrations.
The stalk nitrate test is probably best suited for identifying fields/situations where soil nitrogen uptake was excessive (no yield benefit) and, thus, costly to the grower and possibly the environment. Typical situations where N uptake may be excessive include manured fields or fields following alfalfa that received additional (and possibly unnecessary) nitrogen fertilizer applications for the subsequent corn crop. Some growers may be particularly interested in evaluating the adequacy of their N management program this year given the occurrence of multiple “monsoon” events that likely caused significant soil nitrate-N loss and nitrogen deficiency in the corn crop.
Source: End-of-Season Corn Stalk Nitrate Test – Purdue University, September 15, 2003
This video gives a great overview of how to obtain a proper corn stalk for analysis at a laboratory. The video is roughly 3 minutes long, but it really looks at all facets of sampling in a very, easy to follow manner.