Corn Yield, Plant N Uptake and Environmental N Loss Differences Under Urea and Poultry Litter Application at Different Rates and Timing in Alabama Soils.

In Alabama, poultry is a major industry having a total economic impact of $15.1 billion and generating an estimated 1.4 billion kg of poultry litter (PL). Farmers in the state consider poultry litter as a valuable low-cost nutrient source for row crops especially corn (Zea mays L.). However, there is little information regarding nutrient availability, yield benefits and environmental N losses with respect to PL application rate and time contrary to urea-based fertilization systems in corn production. Therefore, the study compared the application rate and time effects of urea and PL on corn yield, plant N uptake and environmental N losses. The research was conducted at two sites (E.V Smith and Wiregrass) in a randomized complete block design with four replications. The treatments included two N sources applied at two rates i.e. 168 and 336 kg N/ha for urea and a similar N equivalent of PL (2.5 and 5 ton/acre); two application times (single application at planting and split application as 25 % N at planting + 75% N at V6); two urea and PL combinations and a control. Soil and plant samples were collected at V6, V12, R3 and R6 growth stages and analysed for nitrate-N + ammonium-N and total N respectively. Environmental N loss was calculated from the difference between known N inputs and outputs. Preliminary results showed large variability in crop yields among the two sites. Greater grain yields (98.64 bushels/acre highest) with 22 % N use efficiency (NUE) was observed at E.V. Smith with single PL application compared to Urea (75 bushels/acre). In general, corn yields at Wiregrass were greater under urea application (120 bushels/acre highest) than PL with 32% average NUE. No significant differences were observed between single vs split and low vs high application rates.