Residual effects of the organic amendments poultry litter, farmyard manure and biochar on soybean crop

Abstract

The use of organic wastes, as an alternative to inorganic fertilizer, can be an important strategy for Brazilian and tropical agriculture. Despite the importance, few field studies have been done for evaluating organic amendments on soybean crops in Brazil. The study aimed to evaluate the residual effects of the organic amendments poultry litter, farmyard manure and biochar combined with mineral fertilizer on some agronomic attributes of a soybean crop. A field experiment was carried out in a split-split-plot scheme, with three replicates in a randomized block experimental design. The organic sources (plots) at rates of 0, 3, 6 and 9 Mg∙ha−1 (subplots) combined with 0, 100, 200, 300 and 400 kg∙ha−1 (sub subplots) of a mineral fertilizer were applied in 2008. In 2009, only the mineral fertilizer was used on the soybean crop. As a result, all evaluated attributes were influenced by the treatments, except for the number of grains per pod. The application of poultry litter provided the highest yield (3715 kg∙ha−1 using 9 Mg∙ha−1 of the source). A synergistic effect between organic amendments and mineral fertilizer was observed. It was found the possibility of decrease doses of mineral fertilizers by prior use of organic amendments. The most effective dose combination application is 5.5 Mg∙ha−1 of organic amendments associated with 200 kg∙ha−1 of mineral fertilizer to provide optimum yield. The use of organic amendments, rich in nutrients, is a technology to sustainably increase the soybean grain yield.