Effects of different tillage practices on soil water-stable aggregation and organic carbon distribution in dryland farming in Northern China

Knowledge about the changes in soil aggregate stability and soil organic carbon (SOC) under different tillage
treatments is necessary to assess the feasibility of adoption of conservation practices for sustaining productivity
and protecting the environment in dryland farming in northern China. In this study, four treatments, no-till with
strawmulching (NTSM), all straw return tillage (ASRT), shallowrotary treatment (SRT) and conventional tillage
(CT) were set and a 5 years field experiment was carried out to study the effects of different tillage practices on
soil aggregates stability and organic carbon distribution. We found that macro-aggregate (N2 mm and 0.25–
2 mm) proportion, mean weight diameter, total amount, content of SOC in macro-aggregate and proportion of
SOC inmacro-aggregate were significantly improved by NTSM, ASRT and SRT. In all treatments, soil ability to sequester
carbonwas improved more prominently in NTSM, andmacro-aggregate proportion,meanweight diameter,
total amount SOC in macro-aggregate and proportion of SOC in macro-aggregate were improve by
29.4%,30.9%,84.9% and 30.7% respectively by NTSM. In addition, improvement effects on soil aggregates stability
and carbon sequestration ability in ASRT were all higher than in SRT, and compared to NTSM, macro-aggregate
proportion was slightly higher (1.7%) in ASRT, but SOC content and amount in aggregates were remarkably
lower. Our results revealed that reducing soil disturbance, increasing straw returning and especially their combined
application (i.e. NTSM in this study) can effectively be used to reduce soil erosion and improve carbon sequestration
in dryland farming in northern China.