豆科-禾本科牧草混播地土壤氮素对施氮和灌溉的响应

Response of Soil Nitrogen to Nitrogen Fertilization and Irrigation in Leguminous Gramineous Forage Mixed Soil

适当进行施肥和灌溉是提高内蒙古呼伦贝尔地区人工草场生产力、促进恢复的重要措施,建立施氮混播平台和水氮耦合平台,系统分析不同建植模式、不同施氮水平和不同补水条件对草地群落结构功能的影响机制,进而进一步探讨人工草地管理方式的转变对土壤氮素的综合影响,以期为呼伦贝尔地区人工草地种植模式的建立和高效环保管理措施的制定提供一定的理论依据。试验在呼伦贝尔草原生态系统国家野外试验站进行,选取紫花苜蓿、无芒雀麦两种多年生牧草品种,设置紫花苜蓿单播、无芒雀麦单播、紫花苜蓿无芒雀麦1∶1混播3个处理。设置不施氮(N0:0kg N·hm^(-2)·yr^(-1))、低氮(N1:75kg N·hm^(-2)·yr^(-1))和高氮(N2:150kg N·hm^(-2)·yr^(-1))3个处理水平,补水(不补水,旱季补水16%),共72个试验小区,按时间为节点,共11次分别取土壤0~10cm、10~20cm土层深度,测定土壤全氮、土壤铵态氮、硝态氮含量。呼伦贝尔地区建植人工草地时,建议采取紫花苜蓿+无芒雀麦的混播模式,与无芒雀麦单播模式相比,在促进土壤氮素的吸收利用方面更为有效。夏季干旱时期,采取一定的灌溉措施保苗。过量施N对苜蓿单播、无芒雀麦单播吸收氮素效应并不显著,反而会在土壤中大量累积NO_(3)^(-)-N,随着强降雨淋溶到土壤下层形成无效N,造成经济损失同时产生环境污染,但在紫花苜蓿+无芒雀麦混播草地上,高氮和不补水(N2、补水0)条件下可以促进植物对土壤中氮素的吸收。补水与不补水相比,各处理组间土壤铵态氮和硝态氮含量差异不显著,但在雨水充沛的季节过量的补水会导致土壤NO_(3)^(-)-N淋溶到土壤下层形成无效N。呼伦贝尔地区建植人工草地时,采取紫花苜蓿+无芒雀麦混播的种植模式,施氮150kg N·hm^(-2)·yr^(-1)、不补水条件下对于土壤氮素的吸收利用最为有效。

Appropriate fertilization and irrigation are important measures to improve the productivity and the recovery of artificial grassland in Hulunbeir area of Inner Mongolia.A nitrogen-mixed planting and water-nitrogen coupling platform is established.The mechanism of effects of different planting methods,different nitrogen levels as well as different water supply conditions on the structure and the function of grassland community is systematically analyzed,and the effect of the changing of management mode of artificial grassland on soil nitrogen is further discussed.In order to provide a theoretical basis for the establishment of artificial grassland planting mode and formulation of effective environmental protection management measures in Hulunbeir area.The experiment was carried out at Hulunbeier Grassland Ecosystem National Field Test Station.Alfalfa and Bromus inermis were selected as two perennial forage varieties.Three treatments were set up:alfalfa mono-seeding,Bromus inermis mono-seeding and alfalfa Bromus inermis 1:1 mixed seeding.Three treatments(N0:0kg N·hm^(-2)·yr^(-1)),low nitrogen(N1:75kg N·hm^(-2)·yr^(-1))and high nitrogen(N2:150kg N·hm^(-2)·yr^(-1))were set up to water supplement(no water supplement,16%water supplement in arid season).Seventy-two experimental locations were selected at the depth of soil 0~10cm,10~20cm 11 times by timing respectively,to determine the gross nitrogen,ammonium and nitrate contents in the soil.Quantity.In the construction of artificial grassland in Hulunbuir area,it is suggested to adopt the mixed planting mode of alfalfa and brome nigra,which is more effective in promoting the absorption and utilization of soil nitrogen than the single planting mode of brome nigra.During the dry period in summer,some irrigation measures were taken to preserve seedlings.Excessive N application has no significant effect on the absorption of nitrogen by single sowing of alfalfa and brome navii,but will accumulate a large amount of NO_(3)-N in the soil.With heavy rainfall leaching to the soil layer,ineffective N will be formed,resulting in economic losses and environmental pollution.However,in the mixed planting grassland of alfalfa+brome navii,High N and no water supply(N 2,water 0)could promote the uptake of N by plants.Compared with no water supplement,the contents of ammonium nitrogen and nitrate nitrogen in soil were not significantly different among the treatments,but excessive water supplement in rainy season would lead to the leaching of NO_(3)^(-)-N into the lower earth layer to form invalid-N.When artificial grassland was planted in Hulunbuir area,the mixed planting mode of alfalfa and brome amnus was adopted,and the nitrogen application rate of 150kg N·hm^(-2)·yr^(-1) was the most effective for soil nitrogen absorption and utilization under the condition of no water supplement.