Did plastic mulching constantly increase crop yield but decrease soil water in a semiarid rain-fed area?

Abstract

Plastic mulching increases crop yield and water use efficiency (WUE). However, its sustainability in regard to crop productivity and inter-annual soil water balance is widely doubted. This study comprises a long-term field experiment (2010–2019), with spring maize and wheat treated as materials, and two treatments of (1) whole field plastic mulching (PM), and (2) without mulching (CK). The results showed that the soil water storage in the sowing stage decreased significantly in the 100–300 cm profile after 10 years of maize planting in both PM and CK, but there was no significant difference between PM and CK. For wheat, PM on average increased soil water storage by 30.1 mm in the 0–300 cm profile, but CK decreased it by 28.7 mm in the sowing stage in 2019. These results indicated that soil water depletion was caused by maize water uptake not PM. The PM significantly (P < 0.05) increased grain yield of maize and wheat by averages of 276.7 and 82.1 % compared with CK, respectively. Especially in drought years, the grain yield of maize increased by 400.0 and 622.2 % (2011 and 2016, respectively) and of wheat by 405.1 and 231.5 % (2011 and 2017, respectively). The relative variation coefficient of yield and WUE of PM decreased by 101.9 and 207.9 % in maize, respectively, and correspondingly by 48.3 and 47.2 % in wheat compared with CK. Our findings were that (i) soil water depletion depended on crop water uptake characteristics, and the conflict between soil water supply and crop demand was relieved by PM; (ii) PM stably increased crop productivity and maintained the inter-annual water balance; and (iii) PM should be explored widely in semiarid areas, and the plastic waste problem addressed, to ensure future food security.