Evaluating the effects of biodegradable film mulching and topdressing nitrogen on nitrogen dynamic and utilization in the arid cornfield

The residual film and nitrate nitrogen (NO₃-N) leaching are the main sources of non-point pollution in arid fields. To solve the above problems, the DNDC model was first calibrated and validated based on data obtained from plastic film mulching (PM), biodegradable film mulching (BM), and no film mulching (NM) studies performed during 2016 and 2017. The NO₃-N content in 0–50 cm soil layer, leaching, uptake, balance and use efficiency (NUE) under PM, BM, and NM with topdressing nitrogen (N) amount of 280 kg ha⁻¹ (PM₂₈₀, BM₂₈₀, and NM₂₈₀) were evaluated using observed and simulated data. Additionally, scenario simulation and prediction tests were carried out using the DNDC model to explore the critical topdressing N amount for BM, PM, and NM. These factors were compared for BM with topdressing N amount of 160 kg ha⁻¹ (BM₁₆₀) and 220 kg ha⁻¹ (BM₂₂₀). DNDC model showed remarkably high accuracy in simulating the NO₃-N content, leaching, uptake, and yield, with R² and NSE (Nash-Sutcliffe efficiency) of 0.88–0.99 and 0.77–0.99, respectively, during validation studies. During the late growth stage, the corn yield, NO₃-N uptake, content, cumulative NO₃-N leaching (cum.NL), and NUE for BM₂₈₀ showed an average decrease of 4%, 1.44%, 8.81%, 0.75%, and 2.04% than PM₂₈₀, respectively. NO₃-N content and cum.NL increased markedly with increasing concentration of topdressing N. NO₃-N content and cum.NL was increased by 149.03% and 87.33% for BM₂₈₀ and 46.71% and 40.7% for BM₂₂₀, respectively, as compared to BM₁₆₀. The NUE for BM₂₈₀ decreased by 30.56% and 18.25% compared to BM₁₆₀ and BM₂₂₀, respectively. The scenario simulations showed that 200 kg ha⁻¹ is a critical topdressing N application amount for the arid cornfields, with corn yield of 11,132.1 kg ha⁻¹, cum.NL of 121.33 kg ha⁻¹, and NUE of 42.54%, respectively.