Modeling maize water consumption and growth under plastic film mulch using an agro–hydrological model: Searching for the optimal plant density in different hydrological years

Appropriate plant density is essential for crop production in rainfed areas. However, it is quite difficult to obtain the optimal plant density under plastic film mulch in different hydrological years through field experiments due to its limited treatments, and time and labor costs. Therefore, mathematical models are generally used for searching the optimal alternatives. In this paper, the Agro–Hydrological & chemical and Crop systems simulator (AHC) was adopted to model soil water dynamics, rainfed maize growth, and yield under plastic film mulch and various plant density conditions in Northeast China for different hydrological years. The results showed that the AHC model can simulate rainfed maize water use and growth under plastic film mulch and various plant density conditions, i.e., 60,000 (D1), 67,500 (D2), 75,000 (D3), 82,5000 (D4) and 90,000 plants ha−1 (D5). The average maize yields of all treatments in the severely dry (SD), moderately dry (MD), normal (N), moderately wet (MW), and severely wet (SW) years were 11440.3, 13685.4, 13821.5, 14704.8, and 14014.3 kg ha–1, respectively. Compared with non–mulch, plastic film mulch increased the maize basal crop coefficient by 0.08–0.11 and decreased the soil evaporation coefficient by 0.26–0.32, from SD and SW years, respectively. Thus, plastic film mulch augmented maize transpiration by 46.2–76.8 mm, while reduced evaporation by 163.5–186.8 mm across the simulated years. Ultimately, the maize yield under plastic film mulch was 5.9–17.4% higher than that without mulch. From D1 to D5 treatments, the decrease of soil evaporation coefficient was within 0.02 under plastic film mulch and was over 0.05 without mulch. Under plastic film mulch, the relations between plant density and net profit could be well described by the parabolic curves, and the recommended optimal plant densities of maize in the study area were 91, 101, 101, 105, and 101 thousand plants ha–1 in the SD, MS, N, MW, and SW years, respectively. Our findings provide management implications for maize cultivation in the rainfed areas of Northeast China.