Soil carbon and nitrogen fractions and physical attributes affected by soil acidity amendments under no-till on Oxisol in Brazil

Abstract

No-tillage (NT) management has been one of the significant advances in Brazilian agriculture to enhance sustainability. However, weathered soils are acidic and may require amelioration to become more productive. Our objective was to determine the influence of surface application of different sources of soil acidity amendment under NT with different cover crops on soil carbon (C) and nitrogen (N) fractions, soil organic C stock, and soil physical attributes in a clayey Typic Hapludox in Botucatu, São Paulo State, Brazil. A randomized block design was repeated from 2007 to 2013 with main plots of cropping system with different treatments in off-season (forage crop, second crop, cover crop, and fallow) and split plots of soil acidity amendment (no amendment, limestone, and silicate) applied in 2006 and 2011. In 2013, soil was collected at 0–0.05, 0.05–0.1 and 0.1–0.2 m depths. Several soil C and N fractions and micro-porosity were greater (p < 0.05) with Urochloa forage than with other crops, but mainly only at 0–0.05 m depth. Mineralizable C and soil microbial biomass C were greater with application of limestone than without amendment. Application of soil acidity amendments had small, but positive effects on soil C and N fractions and physical properties. Our results suggest that greater crop biomass production in cropping systems under NT are beneficial to enhance soil C and N fractions and soil biological activity, particularly at 0–0.05 m soil depth. Therefore, cover cropping during the dry season in tropical Brazil is recommended to enhance soil condition, but improvements will depend on biomass production potential.