Broiler litter applications and chemical properties of highly weathered soils.

The effect of broiler litter applications on chemical properties of three highly weathered soils of different mineralogy was evaluated. The soils included in the study were Coto (very fine, kaolinitic, isohyperthermic Typic Eutrustox), Consumo (fine, mixed, semiactive, isohyperthermic Typic Haplohumults), and Corozal (very fine, parasesquic, isohyperthermic Typic Hapludults). Five broiler litter treatments (0, 5, 10, 15 and 20 t/ha) were evaluated in a Complete Randomized Block Design with four replications. The soils were incubated for two months at room temperature (23° C). Broiler litter did not increase significantly the pH of the soils; however, soil exchangeable Al3+ decreased in all soils as a result of broiler litter applications. Exchangeable Al3+ in Coto soil decreased from 0.21 cmolc/kg Al3+ in the 0 broiler litter treatment to 0.09 cmolc/kg in the 20 t/ha treatment, in Consumo soil from 1.08 to 0.19 cmolc/kg, and in Corozal soil from 7.57 a 5.76 cmolc/kg. The treatments also increased electrical conductivity of the soils, such an effect being more evident in Coto soil. The 20 t/ha treatment increased soil electrical conductivity of Coto by 74%, whereas for Consumo and Corozal soils the increase was only 55 and 54%, respectively. Available P content in Coto soil increased from 40 mg/kg in the check treatment, to 65 mg/kg in the 20 t/ha manure treatment. In Consumo and Corozal soils no significant change in available P was observed. This finding is indicative of the high P fixing capacity of these soils. It is suggested that soil exchangeable Al3+ in Consumo and Corozal soils is reacting with P in the manure, forming aluminum phosphates and contributing to phosphate fixation. Broiler litter application increased exchangeable K+ and Mg2, but not exchangeable Ca2+, in the three soils; exchangeable Mn2+ increased in Consumo and Coto soils.