Effect of Poultry Litter Application on Crop Yield, Nutrient Uptake and Soil Fertility: A Meta-Analysis.

Extensive research has shown that poultry litter (PL) can be used as a nutrient source for crop production. However, there has been conflicting results as to whether PL application increases crop production when compared to inorganic fertilizer (IF) which explains the need for a comprehensive quantitative review. This study aimed to conduct a meta-analytic assessment to elucidate the influence of PL on crop yield, plant nutrient uptake, and soil fertility as compared to IF. A meta-analysis based on 116 studies and 2293 observations compared agronomic responses to PL and IF application. The log transformed ratio of means was used as effect size (ES) to express differences in the effects of PL and IF. A random-effects model was used to test if the ES was significantly different from zero (α= 0.05). Crop yield was slightly less when evaluating PL additions during the 1^st or 2^nd year of application, while significant increases were observed with long-term PL application. PL’s influence on yield was crop-specific, positive effects on soybean, peanut, corn, and cotton, while negative effects on wheat, barley, and forage production. Plant nutrient uptake was influenced by PL with a slightly negative effect being observed for N uptake, whereas a significant positive effect for P and K uptake. Positive effects on soil fertility were also observed with PL significantly increasing the CEC, pH and concentration of soil C, P, K, Ca, and Mg compared to IF. Overall, PL can be used as an alternative nutrient source to enhance crop yield, increase plant nutrient uptake, and improve soil fertility.