| 摘 要： |
To enhance the potential productivity of forage cultivation, the farming-pastoral zone (connecting the farming area in the eastern part of China and the grassland pastoral area in the western part of China) of Hulunbuir urgently needs to improve water and nutrient utilization efficiency in forage planting. This study conducted a two-year, multi-location field experiment from 2021 to 2022 to evaluate the effects of rainfed farmland (CK), precision irrigation (PI, guided by a 20-cm diameter evaporation pan and soil tensiometer), and traditional farm irrigation (FI, based on key growth stages determined by farmers) on seed yield, water use efficiency (WUE), and nitrogen partial factor productivity (NPFP) of oat (Avena sativa L.) and alfalfa (Medicago sativa L.). Results showed that in the oat experiment, PI and FI significantly increased seed yield by 53.9% and 34.6%, respectively, and NPFP by 69.2% and 39.6%, compared to CK. PI significantly increased WUE by 55.1% compared to FI, while FI decreased WUE in comparison to CK. In the alfalfa experiment, PI and FI significantly increased seed yield by 53.9% and 34.6%, respectively, and NPFP by 26.3% and 15.8%, compared to CK. PI significantly increased WUE by 28.0% compared to FI, and WUE in CK was the lowest. Supplemental irrigation treatments (PI and FI) increased the number of oat spikes and spikelet, contributing to higher oat yields. For alfalfa, these treatments increased reproductive branch numbers, racemes numbers, and seed numbers, enhancing dry matter and seed yield. The increase in oat spikelets and alfalfa seed numbers under PI was more significant than under FI. PI reduced water consumption after oat tasseling (and after alfalfa anthesis) but increased it before tasseling (and before alfalfa anthesis), ensuring early-stage water supply and improving WUE. Under rainfed conditions, the root length density (RLD) of forage (oat and alfalfa) within the 0-60 cm soil depth significantly decreased compared to supplemental irrigation conditions, while RLD below 60 cm was higher than under CK. PI showed greater RLD compared to FI, enhancing water and nitrogen assimilation and utilization in deeper soil layers. PI also resulted in greater overall nitrogen accumulation in forage, reducing nitrate nitrogen content in the soil during maturity. This ensured sufficient nitrogen supply in the topsoil, thereby enhancing nitrogen utilization efficiency. In conclusion, PI significantly improved forage seed yield, WUE, and NPFP by integrating changes in the root system, soil moisture, and nitrogen dynamics. |
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