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Título

ORGANIC CARBON AND SOIL AGGREGATION INDEX IN CROPS ROTATION UNDER NO TILLAGE SYSTEM

Resumo

Crops rotation under no tillage system (NTS) promote continum input of crop residues, affecting the soil organic matter dynamics and the formation and stabilization of soil aggregates and carbon content into them. This study aimed to evaluate the effect of crop rotations in NTS on soil aggregation index and carbon (C) content into aggregates.The field experiment was carried out at the Research Center of the Rural Development Institute of Paraná, at Ponta Grossa, Paraná, Brazil. The treatments consisted of six crops rotation, in a 3-year cycle, arranged in  a randomized block design with four replications. The crops rotation were: I) Wheat (W)/Soybean (S)/W/S/W/S,  II) W/S/Black Oat (O)/Mays(M)/W/S; III) Canola (Cn)/M/W/S/Barley (B)/S; IV) White Oat (WO)/Dry Beans (DB)/Black wheat (BW)/White Lupin (L) + Hairy wetch (HW)/M/Triticale (Tr)/S; V) O + Ryegrass (Rg)/M/O + Rg/S/O + Rg/S; VI) O + HW/M/Tr + Rye (R) + Forrage Pea (P)/DB/BW)/Tr + O + R/S. Soil aggregate samples were collected at depths 0-0.05; 0.05-0.10 and 0.10-0.20 m. The aggregate classification was determined by the wet sieving methodology, and the Weighted Mean Diameter (WMD), Geometric Mean Diameter (GMD) and Aggregate Stability Index (ASI) were calculated. The C content in the aggregates was determined by wet oxidation. The results were submitted to analysis of variance and Tukey test at 5% probability. Regardless of crop rotations the macroaggregates (bigger than 2 mm) were superior to microaggregates. The Aggregate Stability Index differed only in the 0-0,05 m layer, being lower for Rotation I, the less diversified. There was no difference among crops rotation in each depth for WMD and GMD. There was no difference for C content into aggregates among crop rotations in each aggregate class and depth. However, the C content was higher in the superior layer and decresed in depth. the three-year cycle with crops rotation was not enough to express changes in soil C content and aggregation index.

Palavras-chave

Soil structure; Soil organic matter; Soil aggregates

Instituição financiadora

Araucaria Foundation/SETI/SENAR for financial support