CHLOROPHYLL METER READINGS IN CORN AS AFFECTED BY PLANT SPACING

Heightened environmental consciousness has increased the perceived need to improve nitrogen (N) use efficiency by crops. Synchronizing fertilizer N availability with maximum crop N uptake has been proposed as a way to improve N-use efficiency and protect ground water quality. Chlorophyll meters (Minolta SPAD 502) have the potential to conveniently evaluate the N status of com (Zea mays L.) and help improve N management. A potential problem with the use of chlorophyll meters is the effect of within-row plant spacing on meter reading variability. Chlorophyll meter readings and leaf N concentration of irrigated corn at anthesis and grain yield at harvest were measured on plants grouped into eight within-row plant spacing categories. Leaf N concentration was not affected by plant spacings, but chlorophyll meter readings and grain yield per plant increased as plant competition decreased and N fertilizer rate increased. These data indicate that avoiding plants having extreme spacings can greatly increase precision when using chlorophyll meters to evaluate the N status of corn.