EFFECTS OF DIFFERENT TILLAGE AND STRAW MANAGEMENT SYSTEMS ON SOIL AGGREGATION AND CROP YIELD IN RAINFED LOESS PLATEAU

Abstract

Soil aggregation may be affected by soil tillage and crop rotation in dryland areas. The objective of this study was to determine the effects of different combinations of tillage and straw application on soil aggregation in the soil aggregate fractions after fifteen years of spring wheat–field pea rotation. Experimental work included the following treatments: conventional tillage with straw removed (T), no–till with straw removed (NT), no−till with straw retention on the soil surface (NTS) and conventional tillage with straw incorporated (TS). Soil samples were collected to depths of 0–5 cm, 5–10 cm and 10–30 cm from five points in each plot after harvest of the crop in 2015. Wet–sieving method was used to separate four classes of aggregates, named as large macroaggregate (>2000 μm), small macroaggregate (250–2000 μm), microaggregate (53–250μm) and silt and clay (<53 μm). The results showed that compare with T treatment, all conservation tillage methods significantly reduced soil bulk density and increased total porosity. NTS improved soil saturated hydraulic conductivity significantly at 0-30cm. In surface soil (0–10 cm) NTS and TS treatments increased mean weight diameter (MWD) by 19.23% and 12.52% compared with T treatment, respectively. The aggregate content (≥0.25 mm), Mean weight diameter (MWD), Geometric mean diameter (GMD) of the mechanical stable aggregates had significant positive correlation with crop yields. The result of this study suggests that NTS in Lossiah soils may be a better way to enhance soil productivity and improve soil C sequestration potential.