Modeling Spring Maize Grain Filling under Film Mulching and Nitrogen Application in a Cold and Arid Environment

The grain-filling process is a key stage in ensuring a high yield of maize. Nitrogen is one of the nutrient elements most essential for maize, especially in cold and arid areas. To evaluate the effects of plastic-film mulching and nitrogen application on the maize grain-filling process, the impact of different plastic-film mulching (degradable plastic film, J; common plastic-film mulching, P) and nitrogen fertilizer levels (0 kgha(-1), N0; 160 kgha(-1), N1; 320 kgha(-1), N2; 480 kgha(-1), N3) on maize grain-filling characteristic parameters and final 100-kernel weight were tested in 2021 and 2022. The results showed that the interaction between film mulching and nitrogen application significantly (p < 0.05) affected the filling characteristic parameters and final 100-kernel weight of maize. The final 100-kernel weight was highest at the N2 nitrogen application level, which was 7.69-38.13% higher under degradable plastic-film mulching and 3.17-38.06% higher under common plastic-film mulching than at other levels. The nitrogen application level significantly (p < 0.05) increased grain-filling duration and rate. The duration time in reaching the maximum grain-filling rate under the N2 nitrogen application level was around 1.1967-5.7835 d under degradable plastic-film mulching and 2.8688-8.1704 d under the common plastic-film mulching, with the maximum and average grain-filling rate increased by 0.0595-0.2063 gd(-1) and 0.0447-0.1423 gd(-1) under degradable film mulching and 0.1418-0.3058 gd(-1) and 0.1082-0.2125 gd(-1) under common film mulching, respectively. The nitrogen application levels of N2 and N3 under two plastic-film mulching methods prolonged the duration of the rapid and slow increase period of grain filling and increased the grain-filling rate and the average rate. The average grain-filling rate at the N2 level increased by 0.0469-0.1759 gd(-1) and 0.0090-0.0454 gd(-1) under degradable film mulching and 0.1113-0.2581 gd(-1) and 0.0203-0.0648 gd(-1) under common film mulching, respectively. Therefore, common plastic film mainly prolonged the duration of the gradual increase period of grain filling and increased the grain-filling rate; meanwhile, the effect of degraded plastic film on the grain-filling rate increase and prolonging of the grain-filling duration was gradually highlighted during the rapid and the slow period of increase. In addition, the 320 kgha(-1) of nitrogen application level under both common plastic-film mulching and degradable-film mulching was more conducive to prolonging the grain-filling duration of maize, which increased the grain-filling rate and 100-kernel weight, laying a foundation for a high yield of maize.