Soil aggregation indexes and chemical and physical attributes of aggregates in a Typic Hapludult fertilized with swine manure and mineral fertilizer

Abstract

Purpose The objective was to evaluate the effects of mineral fertilizers and swine manure fertilization on soil aggregation indexes and on chemical and physical attributes of aggregates in Typic Hapludult managed under minimum tillage system. Method Experiment was implemented in 2013, in southern Brazil. The treatments were control, mineral fertilization (MF), swine manure compost + MF (SMC+MF); pig slurry + MF (PS+MF); PS to supply N for maize and black oat (PS100). In May 2015 and 2016, undisturbed soil samples were collected to obtain soil aggregates. Aggregates stability was evaluated through the mean weight diameter (MWD) and mean geometric diameter (MGD) indexes and aggregate distribution by diameter classes. In macroaggregates, total organic carbon (TOC), total nitrogen (TN), clay flocculation degree (CF%) and ∆pH were evaluated. Results The use of swine manure, associated or not to MF, increases TOC and TN contents in soil aggregates in 67.02 and 125.87%, respectively, for SMC+MF treatment. However, it was not efficient in improving soil physical attributes, reducing soil aggregation indexes, mainly in the 5-10 cm layer, by the decreased values of MWD and MGD. This result corroborates with the increase in microaggregates in all treatments. This was a result of the negative ∆pH values and the increased CF%. Conclusion Despite the increase in organic matter contents observed in this study, this was not enough to guarantee an improvement in soil physical attributes over 4 years. These results show that management must be supported by several conservationist techniques in order to have soil quality.