Single irrigation can achieve relatively high production and water use efficiency of siberian wildrye grass in the semiarid agropastoral ecotone of North China
Siberian wildrye grass (Elymus sibiricus L.) is widely planted in the agropastoral ecotone of North China (APENC). Scheduled irrigation is an important approach to increase the forage yield in this semiarid region. Based on field experiments conducted in Bashang Plateau in APENC during 2002 to 2004, we studied the feasibility of applying single irrigation (SI) to increase forage yield by bringing the soil water storage in the root zone (0–60 cm) to field capacity at the elongating stage. The results showed that Siberian wildrye grass consumed water most rapidly during the elongating stage. With 48 to 62 mm of water applied during elongating stage, forage yields reached 6000 kg ha–1, a 110% increase compared with no irrigation (NI). With full irrigation (FI) in the growing season, forage yield was only increased by 10% compared with that under SI. The average water use efficiency (WUE) under SI was 1.9 kg m–3, a 76% increase compared with NI or a 10% increase compared with FI. The average irrigation water use efficiency (IWUE) under SI was 10.8 kg m–3 which was almost three times that under FI. Therefore, a single irrigation can be a simple agricultural practice for local farmers, and has great potential to contribute to sustainability of semiarid APENC. In addition, forage yield and WUE showed a quadratic trend with total evapotranspiration (ET). The maximum forage yield in this semiarid area was about 6900 kg ha–1 at 390 mm ET, whereas the maximum WUE was 1.9 kg m–3 at 360 mm ET.