Partitioning evapotranspiration using 18O abundance to understand water use efficiency in maize produced using ridge-furrow mulching system

Abstract

The ridge-furrow mulching system (RFMS) is an efficient farming strategy that has been used widely for improving crop productivity in dryland agriculture. However, the physical mechanism that allows RFMS and its optimal ridge/furrow ratio to drive the efficient utilization of water in fields are unclear. Thus, we conducted a field research for two years with spring maize based on a long-term field experiment in a semiarid region of Northwestern China to quantify evaporation and transpiration, and their relationship with maize growth, yield and water use efficiency (WUE) under RFMS. Three planting patterns of ridge/furrow ratio were tested: (1) RF40, RFMS with 60 cm wide ridges and 40 cm wide furrows; (2) RF60, RFMS with 60 cm wide ridges and 60 cm wide furrows; (3) FP, traditional flat planting (control). Stable oxygen isotope (18O) analysis was used to partition the evapotranspiration (ET) into evaporation (E) and transpiration (T). The results showed that RFMS significantly increased the soil water content (SWC) in the early and late growing season, but not in the middle period (60–120 days after sowing, DAS) when dry matter accumulated rapidly and the highest transpiration occurred. RFMS significantly decreased the nonproductive evaporation, thereby increased the physiologically significant maize transpiration by 25.0–35.7% during the whole growing season. Therefore, the transpiration fraction of ET (T/ET) was 73% and 70% under RF40 and RF60 during the whole growing season, which were significantly higher than FP. Compared to FP, the maize yield and WUE increased significantly by 55.1% and 52.2% under RF40 and by 49.5% and 47.6% under RF60. We found RFMS drives optimization of ET fractions by increased transpiration but decreased evaporation and then improved WUE of maize, higher ridge/furrow ratio (RF40) create uneven line space and higher mulching area in the field, thus drives optimization of ET components and increased yield and WUE the most. Clarification of this physical mechanism improves our understanding of the optimization of maize production under RFMS, thereby helping to optimize the ridge/furrow ratio in semiarid regions.