Dados do Trabalho

Título

LONG-TERM EFFECT OF NO TILLAGE AND COVER CROPS ON ORGANIC CARBON POOLS IN A SOUTHERN BRAZILIAN OXISOL

Resumo

Soil Conservation systems such as no-tillage, with crops rotation including cover crops, can keeping or recovering soil organic matter (SOM). The aim of this study was to evaluate the dynamics of the organic matter pools under soil management systems, no tillage (NT) and conventional tillage (CT), and winter cover crops in rotation with soybean and corn on summers, after 35 years in a clayey Oxisol in Southern Brazil. The CT consists of one plouwing and two disc harrowing, two times a year. The winter species were: hairy vetch, ryegrass, rye, radish, triticale, black oat, white lupin, white lupin + black oat, white lupin + hairy vetch, hairy vetch + black oat, fallow, black fallow. The statistical design was randomized blocks with split plots and three replications. Soil samples were collected on October 2020 at layers: 0-5, 5-10, 10-20 cm. Soil samples also were collected from a native forest adjacent as reference. The fractionation of the SOM was done to obtain labile organic carbon (LOC) and organic carbon associated to minerals (MAOC). The carbon determinations were performed through the wet combustion method. The content and stock of total organic carbon (TOC), LOC and MAOC were higher under no NT, in the 0-5 cm soil layer, because of the high input of crop residues and by no soil disturbance. Otherwise, in the 10-20 cm soil layer, with exception of LOC content, TOC, LOC and MAOC stock were higher under CT, due to two plowing and four harrowing annually, bringing the crop residues to this depth. Regardless soil management system, only for COT content and stock there was difference among the cover crops, being higher for radish, white lupin + black oat and ryegrass, and lower for black fallow. The results show that crops rotation including winter cover crops improved the SOM even in CT over the time (35 years), but the NT was more efficient to recovering organic C stock, with values closer to the natural adjacent forest.

Palavras-chave

Soil organic matter; Crop residues; Conservation systems; Cover crops.

Agradecimentos

Araucaria Foundation/SETI/SENAR for financial support