Abstract:

To clarify the characteristics of dry matter accumulation and the patterns of nitrogen，phosphorus，and potassium uptake and distribution in a sorghum-rapeseed rotation system，and to provide a theoretical basis for precision fertilization，a field positioning experiment was conducted from September 2020 to August 2022. Whole-plant sampling was performed at key growth stages of sorghum and rapeseed to determine dry matter accumulation and nitrogen，phosphorus，and potassium contents in different organs. The results showed that dry matter accumulation in both sorghum and rapeseed followed a "slow then fast" pattern. At maturity of sorghum，dry matter accumulation ranked as grain > stem and leaf > root；at maturity of rapeseed，dry matter accumulation ranked as stem and leaf > grain > pod shell > root. Nutrient uptake exhibited significant stage specificity：for sorghum，the critical period for phosphorus and potassium uptake was 39-64 d（accounting for 67.0% and 57.7% of demand，respectively），and the core period for nitrogen uptake was 65-100 d（accounting for 54.2% of demand）；for rapeseed，the demand for phosphorus and potassium both exceeded 30% during 119-148 d，and nitrogen demand reached 49.7% during the mature stage（168-217 d）. In the sorghum-rapeseed rotation system，the nitrogen，phosphorus，and potassium required for grain production were 35，11，and 46 g·kg^-1 in average，respectively，among which sorghum grain accounted for 24，7，and 31 g·kg^-1，and rapeseed grain accounted for 45，15，and 60 g·kg^-1. This study clarifies the nutrient demand characteristics at each growth stage of the sorghum-rapeseed rotation system，providing data support for scientific fertilization in this system.

Key words: sorghum-rapeseed rotation, nutrient uptake, growth stage, dry matter accumulation