Soybean Response to Poultry Litter and Inorganic Fertilizer

Poultry litter application to fields that will be cropped to legumes is desirable because legumes biologically fix N2 gas from the atmosphere, allowing manures to be applied at rates needed only to satisfy crop P and/or K requirements. The need to export the nutrients in poultry litter from western Arkansas to areas of intensive cropping and fertilizer use plus recent increases in commercial fertilizer prices have increased interest in using poultry litter as an alternative to P and K fertilizers. Soybean [Glycine max (L.) Merr.] yield has responded favorably to poultry litter in Mississippi (Adeli et al., 2005). Initial research in Arkansas comparing soybean yield response to poultry litter and commercial fertilizers (Slaton, unpublished data) has shown mixed results. Trials established at the Rice Research Extension Center (Dewitt silt loam) and Northeast Research Extension Center (Sharkey-Steele complex) showed no yield benefit from poultry litter or equivalent P and K rates from commercial fertilizers on soils that had high soil-test K and medium or lower soil-test P. However, several trials established on silt loam soils west of Crowley’s Ridge have shown significant yield increases from poultry litter that were sometimes greater than yields produced with equivalent rates of P and K fertilizer. Our primary research objective was to evaluate soybean yield and leaf nutrient concentration responses to poultry litter compared to various inorganic fertilizer combinations. The overall goals of this research were to determine the availability of P and K in poultry litter and establish whether poultry litter provided any potential yield benefits above those provided by adequate rates of commercial fertilizers.