Abstract

COMMUN. SOIL SCI. PLANT ANAL., 30(7&8), 1037-1049 (1999)

Using a Chlorophyll Meter to Manage Nitrogen Applications to Corn with High Nitrate Irrigation Water

Charles A. Shapiro

Northeast Research and Extension Center, Haskell Agricultural Laboratory, University of Nebraska, Concord, NE 68728-2828

ABSTRACT

Chlorophyll meters can aid in measuring the nitrogen (N) status of corn (Zea mays), but will the use of chlorophyll meters decrease total N use or increase corn grain yield? Use of a fully fertilized reference strip with a chlorophyll meter (SPAD 502) is an accepted management strategy. The critical level of relative chlorophyll necessary to trigger supplement N is uncertain. To determine the impact of using a 96 or 92% critical level of chlorophyll readings relative to a fully fertilized reference strip, 0 and 112 N kg ha^-1 were applied at planting for three years. Specific plots were fertilized with an additional 56 kg N ha^-1 whenever the meter reading on those plots was below either 96 or 92% of the reference area. The experiment was conducted on two Typic Haplustolls and an Entic Haplustoll. Irrigation water contained nitrate ranging from 20 to 38 mg L^-1. Irrigation water supplied from 43 to 120 kg N ha^-1 season^-1. For all treatments that received N-supplements based on the chlorophyll meter, yields were statistically the same. The chlorophyll meter is a useful management tool to help schedule N applications, when irrigation water is contaminated with nitrate since use of the chlorophyll meter prevented any yield limiting N deficiencies.

G93-1171-A Using a Chlorophyll Meter to Improve N Management