Responses of productivity to film mulching patterns and chemical fertilizer application rates in maize/pea intercropping system

To investigate the response of productivity to mulching patterns and chemical fertilizer application rates in intercropping and monoculture cropping systems, we used a long-term maize/pea intercropping field experiment located in Zhangye Water-saving Agricultural Experimental Station of Gansu Academy of Agricultural Sciences. The experiment started in 2012 and has three factors. The first factor is two film mulching patterns, i.e. strip mulching and full mulching; the second factor is two chemical fertilizer application rates, i.e. conventional fertilization with 450 kg(N)·hm⁻² and 78.6 kg(P)·hm⁻² and reduced fertilization with 300 kg(N)·hm⁻² and 52.4 kg(P)·hm⁻². the third factor is three cropping systems, i.e. maize monoculture, pea monoculture, maize/pea intercropping; Plant samples were collected at the harvest stage of pea and maize in 2021 and 2022, and the grain yield, aboveground biomass, crude protein yield (calculation based on grain nitrogen concentration), and phosphorus uptake of grains were measured. The results showed that the yield of intercropping system was the highest; the grain yield of the intercropping system was significantly higher than that of the weighted mean of monoculture by 32.4% across two years; the yield advantages mainly come from the positive complementarity effect rather than the selection effect. In addition, land equivalent ratio (LER) was greater than 1 in each treatment, indicating that intercropping exhibited a greater land use efficiency than monoculture. On average for two experimental years, compared with monoculture, intercropping increased grain crude protein yield and grain phosphorus content by 30.0% and 24.0%, respectively. Full mulching significantly enhanced productivity and crude protein yield compared with strip mulching, in which compared with monoculture combined with strip mulching, intercropping with full mulching significantly increased grain yield, crude protein yield, partial productivity of nitrogen and phosphorus fertilizer by 47.0%, 57.5%, 47.5% and 47.3%, respectively. The yield of intercropping was 38.4% and 26.3% higher than that of monoculture under strip mulching and full mulching treatment, respectively. Under monocropping and intercropping conditions, the yield of mulching was 15.9% and 5.8% higher than that of strip film, respectively, i.e. intercropping combined with full mulching enhances nutrient use efficiency. There was no significant difference in yield between the two fertilization levels. Under the reduction of NP chemical fertilizer treatment, intercropping system increased the partial productivity of fertilizer and maintained productivity and crude protein yield compared with conventional fertilizer application rate. In conclusion, intercropping under reduced fertilization of full film mulching is more sustainable than farmer's custom (i.e. maize monoculture with conventional fertilization under strip mulching), which enhances productivity and save chemical fertilizer.