Applying stable isotopes to illuminate the mechanism of water use in wheat fields under ridge-furrow planting with plastic film

Abstract

As an efficient water and soil conservation tillage practice, ridge-furrow planting with plastic film (RP) is rarely used in humid and sub-humid areas. It is hypothesized that RP could break the bottleneck of flat planting (FP) in sub-humid areas that makes it difficult to improve wheat yield. Before recommending RP, it should be clarified how RP promotes the efficient utilization of water in fields. Therefore, we conducted a 2-year field experiment following a randomized block design with winter wheat under FP and RP in the Guanzhong Plain. Stable isotopes of δ²H and δ¹⁸O were used to quantify precipitation infiltration, root water uptake (RWU), and evaporation (E) and transpiration (T). The results showed that the average contribution proportion of precipitation to 0–100 cm soil layer under RP significantly increased by 10.4–22.9 % versus FP within five days after precipitation. RP also increased the average RWU proportion by 8.6 % in the 0–60 cm layer and decreased it by 28.1 % in the 60–200 cm layer compared to FP. Furthermore, RP significantly decreased E by 36.9 % and increased T by 8.9 % versus FP from greening to harvest stage, resulting in significantly depleted δ²H and δ¹⁸O values in soil water. Ultimately, the two-year average grain yield and water use efficiency (WUE) of winter wheat under RP increased significantly by 19.1 % and 21.6 % in comparison to FP, respectively. Overall, RP can conserve soil water by promoting precipitation infiltration and inhibiting E, thereby increasing T and improving grain yield and WUE. This study bridges the gap between theoretical research and practical dissemination of RP in the sub-humid region, and provides an empirical support for soil and water conservation and yield enhancement.