Nutrient accumulation from excessive nutrient surplus caused by shifting from rice monoculture to rice–crayfish rotation

The potential environmental risk associated with nutrient surplus after switching from rice monoculture (RM) to rice–crayfish rotation (RCR) was assessed in the Jianghan Plains in China. Nutrient surplus was achieved by surveying 32 RM and 69 RCR and determining their nutrient inputs and outputs, and the soil nutrient status for different soil properties were recorded for 0–23 years. The annual average input of N, P2O5, and K2O in RCR was 536, 185, and 253 kg ha−1, respectively, wherein fertilizer and feed accounted for the major fraction of the total nutrient input. For instance, they accounted 58% and 18% of N, 74% and 24% of P2O5, and 70% and 30% of K2O, respectively. The annual apparent surplus of N, P2O5, and K2O was 397, 145, and 225 kg ha−1, respectively, leading to low apparent nutrient use efficiency. Consequently, compared with RM, the total N and soil readily oxidized organic carbon in the upper soil surface (0–20 cm) for the RCR field significantly increased by 0.42–0.96 g kg−1 and 1.63–3.19 g kg−1, respectively. The available N, Olsen P, and exchangeable K of the RCR in the upper soil layer also increased significantly. In the RCR system, a significant positive linear relationship between the apparent accumulated nutrient surplus of N, P, and K elements and the total N, Olsen P, and exchangeable K present in the 0–60 cm soil profile was observed. In RCR, the soil pH in 0–60 cm soil profile and cation exchange capacity in the 0–20 cm soil layer increased as the cultivation time progressed. Nutrient accumulation in the soil not only enhanced soil fertility but also negatively influenced the environment. Therefore, several measures (e.g., new fertilization technologies, new fertilizer, legislation approaches for nutrient surplus, and technical training) should be adopted to control the nutrient surplus. [Display omitted] •The annual apparent surplus of N, P2O5 and K2O were 356, 145, 225 kg ha−1 in rice-crayfish systems.•Total N and soil readily oxidized organic carbon of rice-crayfish systems in 0–20 cm soil layer significantly increased.•Nutrient accumulations existed due to excessive nutrient balance surplus in rice-crayfish rotation. The main finding: Nutrient surplus in the RCR soil enhanced nutrient accumulation, but it should be precisely monitored to avoid environmental pollution.