Optimum Poultry Litter Rates for Maximum Profit versus Yield in Cotton Production

Abstract

Cotton (Gossypium hirsutum L.) lint yield responds well to increasing rates of poultry litter fertilization, but little is known of how optimum rates for yield compare with optimum rates for profit. The objectives of this study were to analyze cotton lint yield response to poultry litter application rates, determine and compare rates that maximize lint yield (PLy) vs. profit (PLp), and identify a practical approach for estimating PLp. Cotton planted on two farms that used conventional and no‐tillage systems were fertilized with seven target rates of litter from 0 to 13.5 Mg ha−1 or with a farm standard treatment receiving synthetic fertilizers (Std). The PLy and PLp for each year and farm were determined from current cotton and poultry litter prices and response curves fitted into lint yield and actual applied litter rates. The results showed that cotton lint yield peaked at an average across years of 1430 kg ha−1, with 11.1 Mg ha−1 PLy in the conventional tillage system and at 1354 kg ha−1 with 13.2 Mg ha−1 PLy in the no‐till system. These peak yields exceeded the respective Std treatment yields but were not the most profitable. Maximum profit in both tillage systems was achieved with 7.8 Mg ha−1 PLp, which resulted in lint yields of 1367 and 1253 kg ha−1 in the conventional and no‐till systems, respectively. The PLp in both systems was similar to the poultry litter rate that resulted in lint yield equal to the Std (PLs), which suggests that applying litter to provide plant available N equal to the farm standard practice for synthetic N fertilizers is a practical method for estimating PLp.