UC Riverside

Drip irrigation under plastic film mulching with applications of the N-fertilizer is an excellent agricultural strategy, resulting in saving irrigation water, improving N use efficiency, and increasing crop yield. However, the film residue and nitrate-nitrogen (NO3-N) losses are the leading cause of non-point pollution in agricultural fields. To promote the development of sustainable agriculture, the HYDRUS (2D/3D) model was first calibrated and then validated using experimental data from 2016 and 2017, respectively, collected in the drip-irrigated sandy field with plastic film mulching (PFM), biodegradable film mulching (BFM), and no film mulching (NFM). Additionally, the NO3-N spatial and temporal distributions, uptake, leaching, and use efficiency (NUE) under PFM, BFM, and NFM with 280 kg ha−1 of the N-fertilizer (the local recommendation) were evaluated using both observed and simulated data. These factors were also assessed under BFM with 210 (75 % of the recommended value) and 140 kg ha-1 (50 % of the recommended value) of the N-fertilizer. The results of numerical simulations were in good agreement with observations, with the RMSE, R2, and NSE during verification being 0.01-0.08 mg cm-3, 0.62-0.87, and 0.68-0.94, respectively. When the same amount of the N-fertilizer (280 kg ha−1) was applied in each treatment, there were no apparent differences in NO3-N concentrations in the soil profile, cumulative NO3-N uptake by corn (CNU), and cumulative NO3-N leaching (CNL) in the 100-cm soil depth between the BFM280 and PFM280 scenarios (the subscript indicates the amount of the N-fertilizer) during the early growing season (Day After Sowing [DAS] of 0–78 in 2016 and DAS of 0–92 in 2017). However, CNU and CNL were higher, and the NO3-N concentrations in the upper soil layer (0−40 cm soil layer) lower in these two scenarios than in the NFM280 scenario. The NO3-N concentrations in the topsoil layer (the 0−20 cm soil layer) in the BFM280 scenario were 3.9 % higher than in the PFM280 scenario during DAS 93–154 in 2017 due to the disintegration of the biodegradable film and 26.3 % lower during DAS 79–155 in 2016 because of intensive rainfall. Additionally, the highest NUE (50.9 kg kg-1, the average value for two years) was found when 75 % of the recommended N-fertilizer (210 kg ha−1) was applied. Therefore, an application of 210 kg ha−1 of the N-fertilizer in the BFM scenario can be recommended for sandy farmland to avoid plastic pollution, increase NUE, and effectively promote the development of sustainable agriculture.