Changes in soil physical and chemical properties with the use of poultry litter in an Oxisol of southern Brazil

The use of poultry litter in agriculture poses potential risk to soil because of its composition, including elements that act as dispersants and negatively affect soil properties. More research is needed in this area as there is still insufficient data on optimal application rates. This study aims to fill the knowledge gap on the effects of poultry litter application on soil chemical and physical properties in an Oxisol region of southern Brazil managed under a no-tillage system (NT). The experiment included rates of poultry litter (3.6, 7.2, and 10.8 Mg ha^-1), control treatment and chemical fertilization (NPK) in a randomized block design with four replications. The results showed that although the application of poultry litter increased the organic matter (OM), it did not significantly improve the geometric mean diameter of the soil. The study refuted the hypothesis that OM from organic fertilizers could reduce clay dispersion or improve soil aggregate stabilization. Instead, it was found that the increase in Na⁺, with high pH and Ca²⁺ levels contributed significantly to increased clay dispersion. This was evident in treatments with poultry litter rates of 7.2 and 10.8 Mg ha^-1. PCA showed that soil chemical properties (Na⁺, pH, K, Mg²⁺, Ca²⁺ and OM) are correlated with CDW, indicating their direct influence and the need for caution when using poultry litter in agriculture. It is concluded that the application of poultry litter at rates above 7.2 Mg ha^-1 leads to increased pH, Na⁺, K, Mg²⁺ and Ca²⁺ levels, exacerbating clay mineral dispersion in an Oxisol under a NT.