Diversifying crop rotation improves productivity of oilseed flax by increasing soil carbon sequestration and soil biological health

Diversified crop rotations are proposed to enhance agricultural system productivity, stability, and climate resilience. Oilseed flax, a crucial oilseed crop in rain-fed agricultural systems of China, faces increasing challenges under climate change due to conventional monoculture practices. Therefore, our eight-year field experiment in northwest China's rain-fed region assessed how integrating potato and wheat into flax monoculture affects oilseed flax productivity and soil health. The research results revealed that: In initial years, diversified rotation increased oilseed flax productivity and soil carbon sequestration, with minor positive effects on soil bacterial communities. As rotations progressed, these benefits amplified due to accumulated system functionality and increased precipitation. The wheat → potato → wheat → oilseed flax (WPWF) treatment achieved the maximum average grain yield of oilseed flax (70.2 % increase) and sustainable yield index (SYI, 63.9 % increase) over two crop rotation cycles, alongside a lower coefficient of variation (CV), compared with continuous oilseed flax monoculture (Cont F). Notably, soil carbon sequestration and bacterial diversity correlated positively with the oilseed flax productivity. Overall, soil organic carbon (SOC) storage under the crop rotation systems increased by 8.4 %−19.9 % and 10.7 %−30.7 %, respectively, compared with the Cont F in 2016 and 2020. Through integrated comprehensive evaluation and economic benefits analysis, the WFPF and WPWF systems are validated as regionally optimal rotations. It provides farmers with flexible implementation options to select context-adapted sequences based on local conditions. This study highlights diversified crop rotations as essential for long-term food security, soil health and farmers' income growth. Fig. 1 Illustration of rotation system from problems to results. On the Loess Plateau of Northwest China—the case study area, the oilseed flax monoculture (continuous cropping) often leads to low oilseed flax productivity, soil nutrient depletion and soil fertility decline. In contrast, diversified crop rotation systems involving local staple food crops such as potatoes and wheat increase soil carbon sequestration by returning large amounts of crop residue to the soil and stimulating microbial activity, benefits that can increase oilseed flax productivity. • Crop rotation boosts oilseed flax yield and enhances soil carbon sequestration. • Crop rotation benefits exhibit a significant long-term cumulative effect. • Reducing homologous crop frequency improves yield stability and sustainability. • Adequate precipitation mitigates yield losses from extended continuous cropping.