Long-term evaluation of poultry litter as a source of nitrogen for cotton and corn

Land application of poultry broiler litter (BL) in agricultural production is a widely used practice. However, cotton (Gossypium hirsutum L.) growers in poultry-producing regions of the southern USA have been reluctant to use BL as a crop nutrient source. Field experiments were conducted for 13 yr to study the effect of BL application to cotton and corn (Zea mays L.) under conventional and conservation tillage systems. Nitrogen rates from 0 to 269 kg ha(-1) were applied annually at two locations to compare the effect of BL and ammonium nitrate (AN) as N sources. The relationship between the total N rates (N) applied and the relative N availability (y) based on the crop yield by application of BL and AN is described by linear equation: y = 71.58 + 0.15N (r = 0.66). In most years, there were no differences in relative yields from total N applied as BL or AN. The amplitude of yield increase based on N source varied with rainfall during the growing season. The residual effect of BL in the second year after application resulted in 30 to 50% of the cotton lint yield and 25 to 65% of the corn grain yield that resulted from a standard N fertilization rate. General observations suggest that N availability from BL is similar whether surface-applied as in conservation tillage systems or incorporated as in conventionally tilled systems.