冬灌改善牧草越冬期冻旱胁迫的作用与机理

It is a global problem that frozen and drought cause great damage to crops. The critical factors lead to poor pasture are freeze injury caused by low temperature in pasture wintering period and pasture water shortage caused by drought in spring. Aim at the problem that frozen and drought stress during pasture wintering period, this research ameliorate frozen and drought stress during pasture wintering period by winter irrigation. Reveal the effect and mechanism of frozen and drought stress on pasture, plot experiment and laboratory analysis will be conducted, with artificial grassland and natural grassland as case. Rules will be analysis include the key factors variation of surface layer and soil environment, pasture moisture and physiological reaction. The mechanism of ameliorating frozen and drought stress through winter irrigation will be revealed, combine the result of pasture physiology development, yield and quality. The best winter irrigation program to reply frozen and drought stress during pasture wintering period will be proposed. Research achievement must be significance in theory to relieve the disaster forming process by frozen and drought stress, to rich grassland irrigation.

冻旱灾害造成作物产量损失是全球性的问题。低温对牧草越冬期造成的冻害和春季干旱造成的牧草缺水是导致牧草低产的关键因素。针对牧草越冬期受冻旱胁迫这一问题，从冬灌改善牧草越冬期冻旱胁迫的新角度，以人工草地和天然草地为研究对象，采用小区试验和实验室分析实验，研究牧草越冬期冬灌改善牧草的生长与产量品质指标，明确冬灌改善牧草冻旱胁迫的作用。分析不同冬灌灌溉制度下近地层环境及土壤环境关键要素与牧草根系的变化规律和牧草水分生理反应规律，结合牧草生理生长与产量品质形成的结果，揭示冬灌改善牧草冻旱胁迫的机理。提出牧草越冬期应对冻旱胁迫的最佳冬灌灌溉制度。研究成果对于延缓冻旱胁迫成灾过程，丰富草原灌溉理论，促进牧草优质高产具有较好的科学意义和实用价值。

越冬期冻旱胁迫是导致多年生牧草低产的关键因素，冻旱灾害造成作物产量损失是全球性的问题。近年来，我国饲草地建设规模的迅猛发展迫切需要研究提高饲草地作物返青率和产量的田间管理措施，随着气候异常变化加剧，降雨时空分布更加不均匀，温度的急剧变化更加频繁，局部地区冻旱灾害呈多发态势，在北方草原牧区表现的尤为突出。项目以北方地区广泛种植且易受冻旱的典型牧草紫花苜蓿为例，采用小区试验和室内实验，分析冬灌条件下土壤环境、牧草生长发育、水分生理反应等指标的变化规律，研究冬灌改善牧草冻旱胁迫的作用与机理。结果表明：. （1）冬灌措施下土壤水分得以增加，一定程度抑制了越冬期土壤温度的波动幅度，改善了牧草越冬期生境条件，促进了苜蓿的安全越冬。水分运移数据表明滴灌条件下封冻水灌溉后第3天灌溉水稳定分布于根系层，高水量封冻水灌溉处理下苜蓿根系对水分有一定的吸收，且主要集中于土壤10、40、50cm深度处；中水量、低水量封冻水灌溉处理下，苜蓿根系入冬前未吸收灌溉水。. （2）依据苜蓿越冬期根系多项生理指标综合评价，融冻水灌溉可以显著提高苜蓿的抗寒性。中水量融冻水灌溉对苜蓿抗寒性的提高效果最好，根系活力增加幅度最大。随着冬灌水量的增加苜蓿越冬率及产量有增加的趋势，原因在于冬灌提高了苜蓿的越冬成活率、活性植株密度和数量。可见冬灌切实具有改善牧草越冬期冻旱胁迫的作用。. （3）综合土壤温湿度、水分运移、牧草生育指标、牧草生理信息等试验数据，初步确定冬灌优化灌溉模式为高水量封冻水+中水量融冻水灌溉。封冻水灌溉选择在日平均气温为3℃时，融冻水灌溉选择在日最低气温持续-4℃时较为适宜。. 从牧草越冬期冬灌这一新的角度开展冻旱灾害减灾作用与机理的研究，对于丰富草原灌溉理论具有较好的理论意义，对于促进牧草优质高产具有较强的实用价值。