不同灌溉量对内蒙古人工草地主要牧草产量和水分利用效率的影响

人工草地建设是缓解内蒙古地区草地生存压力的必要途径,而水分短缺是该区人工草地建设中牧草生长的主要限制因素,适量的人工补水以实现牧草的高产节水是解决这一问题的关键。以当地主要牧草冰草和紫花苜蓿为研究对象,开展单播和混播条件下不同灌溉量对牧草产量、光合性能和水分利用效率影响的对比试验。研究结果表明:(1)豆禾混播有利于提高冰草和紫花苜蓿的产量;(2)8月初现蕾期是冰草和紫花苜蓿收割的最佳季节,此时牧草产量最高;(3)灌溉量达到田间持水量的45%(包含降雨量在内的单位面积灌溉量在7月初达到903.8 m3/hm2,在8月初达到1812.4 m3/hm2)是牧草高产节水的最佳补水选择;(4)6—8月水分胁迫更有利于提高牧草的长期水分利用效率(long-term water use efficiency,WUEL),开花期后补水对提高牧草WUEL的作用开始显著;(5)在牧草产量最高的8月初水分胁迫更有利于提高牧草的瞬时水分利用效率(instantaneous water use efficiency,WUEI),而在7月初光照强烈、水分蒸发量大时,较多地补水更有利于提高牧草的WUEI。

Analyzing the impact of irrigation quantity on biomass and water use efficiency of main grasses in artificial grassland in Inner Mongolia

The construction of artificial grassland is the necessary way to alleviate pressures on the grassland in Inner Mongolia. Water shortage is the major limiting factor for grass growth in artificial grassland in this region. Suitable irrigation quantity is the key to solve the problem of water shortage by both increasing grass yield and saving water. In this study, we selected two local typical grasses Agropyron cristatum and Medicago sativaL and conducted irrigation experiments with single sowing and mixture sowing of the two. Then comparative analyses were explored on biomass, photosynthesis and water use efficiency of the two grasses under different irrigation schemes. The results show that: (1) The mixture sowing of leguminous herbage and gramineous herbage is helpful to enhance the yields of the two plants.; (2) Squaring period in the early August is the best season for the harvesting of Agropyron cristatum and Medicago sativaL, when the yields of the grasses are the highest; (3) Treatment 3, of which the irrigation quantity is up to 45% of the field capacity, the amount of water recharge per unit (including precipitation and irrigation) is 903.8 m³/hm² in early July and 1812.4 m³/hm² in early August, is the best water treatment choice for both grass yields increase and water-saving; (4) Rain-fed condition or irrigating a little water (treatment 3) is effective to increase long-term water use efficiency (WUEL) of the grasses from June to August. Irrigating more water (treatments 1 and 2) started to affect WUEL only after entering the flowering stage of the grasses; (5) Rain-fed condition or irrigating a little water is effective to increase grass leaf instantaneous water use efficiency (WUEI) in early August. However, because of intensive sunlight, water evaporation is high and it is more effective to increase WUEI by irrigating more water in early July.