Long-term effects of tillage and straw management on soil organic carbon, crop yield, and yield stability in a wheat-maize system

A long-term experiment for testing different tillage methods and straw management practices was carried out in the Northern China Plain (NCP) since 2002 in a double cropping system (winter wheat and summer maize) rotated annually. Data for 11 yr (2005–2015) was collected to compare the long-term effects of six agricultural practices on soil organic carbon (SOC) storage, crop yield, and yield stability. The six agricultural methods comprised of two main factors (i) tillage practices with three modalities—conventional tillage (CT), no-tillage (NT), and subsoiling (ST); and (ii) straw management with two modalities—straw return (S) and straw removal (0). Here, straw was usually defined as crop residue cut and removed with harvest. Finally, the six treatment combinations were represented as CT0, NT0, ST0, CTS, NTS, and STS. The SOC storage showed similar dynamic changing trends under all treatments, but was higher in NT and ST and straw return plots than in CT0 plots. Average SOC storage under STS and NTS reached 14.1, and 13.1 g kg−1, respectively. After 2005, both tillage practice and residue management affected SOC storage significantly. Cumulative yields for 11 yr with maize and wheat were higher for ST than NT and CT both with straw removal and straw return. Average crop yield increased by 6.2 and 20.1% in winter wheat and by 11.0 and 21.6% in summer maize, respectively, in ST0 and STS, when compared to CT0. NT, ST, and straw return increased crop yield stability, with STS being the most stable. Variability in STS was only 11.3% for winter wheat and 8.8% for summer maize. Pearson correlation analysis showed that winter wheat and summer maize yields were significantly and positively correlated with SOC storage. Subsoiling with straw return (STs) did not result in higher SOC than NTs after 11 yr, but it resulted in the highest cumulative yield for wheat and maize, and the highest yield stability for wheat. When straw was removed, SOC after 11 yr was highest for NT, but cumulative yields for wheat and maize were highest for ST. STS is firstly an optimal method to improve SOC storage, crop yield, and yield stability in the NCP.