Impact of conservation tillage and intensifying crop rotations in enhancing soil carbon, microbial cycling and aggregation in semiarid agro-eco systems: A review

Abstract

Tillage influenced SOC and microbial cycling but most effects were observed at 0–5 cm rather than 5–15 cm. Reduced tillage (RT) in a continuous monoculture increased SOC by 24% compared to conventional tillage (CT) at 0–5 cm, but tillage had no effect at 5–15 cm. Crop rotation increased soil C contents compared to continuous monocropping rotation under CT increased SOC by 28% at 0–5 cm compared to CT continuous monocropping. Reduced tillage increased soil microbial biomass C (MBC) by an average of 11 and 18% compared to CT continuous monocropping and the adoption of crop rotation, respectively, while microbial biomass N (MBN) for RT was 62% greater than for CT. NT (no-till with residue) and RTW (rotary tillage with residue) treatments significantly increased the proportion of macroaggregate fractions (>2000 and 250-2000 im) compared with the MP-R (moldboard plow without residue) and MP+R (moldboard plow with residue) treatments. Averaged across all depths, mean weight diameters of aggregates (MWD) in NT and RT were 47 and 20% higher than that in MP+R. Aggregate stability in continuous rotations was about twice that in wheat-fallow rotations. Fungal biomass was three times greater in continuous rotations than wheat fallow, but was not significantly different from mid-intensity rotations.