Modeling the biogeochemical effects of rotation pattern and field management practices in a multi-crop (cotton, wheat, maize) rotation system: a case study in northern China

Abstract. The cropping system with rotations between cotton and winter wheat−summer maize (W–M) is widely adopted in northern China. Optimizing the rotation pattern and related field management practices of this system is crucial for reducing its negative impacts on climate and environmental quality. In this study, the approach applied to identify the optimal rotation pattern with the best management practice (BMP) relied on biogeochemical model simulations to determine the negative impact potential (NIP) of individual management options/scenarios and a set of constraints. The optimal rotation pattern and related BMP are referred to as the scenario with the lowest NIP that satisfies the given constraints. All the variables of interest were generated by simulation of the DeNitrification-DeComposition 95 version (DNDC95) model. The DNDC95 model validations performed previously for a land cultivated with the W–M and presently for an adjacent area cultivated with cotton showed satisfactory performance in simulating the variables of interest with available observations. The simulations of rotation patterns indicated that proper rotation of cotton and the W–M can simultaneously benefit crop yields, soil carbon sequestration and greenhouse gas mitigation. The three-crop rotation pattern in a 6-year cycle could be optimized with 3 consecutive years of cotton and 3 continuous years of W–M cultivation. The experiments with 108 management scenarios showed that the BMP for the optimized rotation pattern involved using 15 % less nitrogen fertilizer (i.e., 94 and 366 kg N ha −1 yr −1 for cotton and the W–M, respectively) and 20 % less irrigation water (i.e., 60–180 and 230–410 mm yr −1 for cotton and the W–M, respectively) by sprinkling than the conventional practices, fully incorporating crop residues, and adopting the current deep tillage (20–30 cm) for cotton but the reduced tillage (10 cm) for the W–M. However, field confirmation of these BMPs resulting from the model-based virtual experiments is still required.