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

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.

ACKNOWLEDGMENTS

The authors are grateful to the Georgia Commodity Commission for Corn for their financial support of this project. We thank Benjie Baldree, Ellen Hall, Robert Bennett, Candice Purvis Sheffield, William Sheffield, Karen Baldree, and Elaine Miller for field and laboratory work.