DETERMINING SIDE-DRESS NITROGEN REQUIREMENTS OF CORN FOLLOWING BROILER LITTER IN THE SOUTHERN COASTAL PLAIN

Abstract

ABSTRACT Nitrogen (N) fertilizer is a major cost factor for growing irrigated corn (Zea mays L.) in low N status sandy Southern Coastal Plains soils. Use of broiler litter, from the rapidly expanding broiler industry, can provide a significant portion of the N needed for corn, but little research has been available to determine the best method for determining N needs following broiler litter applications. Seven experiments were conducted in three years to determine if the SPAD meter could predict the need for N-side dressing, both following and not following litter application. The experiments were split-plots with three rates of broiler litter (0, 4.5, and 9.0 Mg/ha) as main plots. The split plots included well-fertilized reference plots (336 kg N/ha), fully fertilized plots (224 kg N/ha), and plots receiving either 56 or 112 kg N/ha at V6, V8, and/or at R1 when readings were<95% of the reference plots. Mean grain yields were greatest where broiler litter was applied, but was not greater in plots receiving 9.0 Mg/ha than where 4.5 Mg L/ha was applied. However, less N fertilizer was required at the 9.0 Mg rate when N-credits were provided for the N released from the litter. Profitability where litter was applied was greater when N-credits were given for previous crop and litter than when either of the SPAD methods were used to guide side-dress N decisions. It is concluded that the SPAD meter, as used in this study, is not a viable tool for guiding N side-dress decisions for corn in the Southern Coastal Plain.