作 者 ：张晓红,徐炳成,李凤民.

期 刊 ：中国生态农业学报 2008年 16卷 4期 页码：810-817

关键词：黄土旱塬；豆科牧草；播种方式；播种密度；土壤养分剖面分布；土壤养分平衡；

Keywords:Highland Loess Plateau, legume, Seeding mode, Seeding density, Nutrient distribution along soil profile, Nutrient equilibrium,

摘 要 ：为了解豆科牧草短期种植对土壤养分环境影响的进程和规律，通过田间试验对沙打旺、苜蓿和胡枝子等3种豆科牧草以不同密度单播、混播对土壤有机质、全氮、全磷剖面分布和平衡输出的影响进行了定性和定量分析。所有处理土壤全氮和有机质含量在土壤剖面2 m深度范围内均呈典型的“S”形分布，全磷呈抛物线形分布。单播牧草固氮能力与播种密度呈正相关; 苜蓿固氮能力最强，高密度下表观生物固氮量达507.5 kg·hm^-2。沙打旺生长1年可使土壤有机质平均净增 3.51%。沙打旺和苜蓿全磷平均输出比率分别为43.14%和40.24%，显著高于胡枝子（23.74%）；胡枝子与沙打旺、苜蓿的两两混播处理和3种牧草混播处理平均全磷输出比率分别为20.73%、26.33%、25.83%。试验结果表明，3种豆科牧草均可显著提高土壤有机质累积，沙打旺和苜蓿对土壤全氮和全磷的消耗显著大于胡枝子，但前两者的固氮能力也强于后者。以适当密度进行的不同牧草混播处理由于种间良性竞争和共生协调作用可优化混播群体对土壤养分的消耗利用。

Abstract:In order to understand the short-term impact of legumes on soil nutrient condition, three types of legumes:Astragelus adsurgens (A), Medicago sativa (B) and Lespedeza davurica (C) were seeded at different densities either alone or mixed, and the distribution and equilibrium of soil organic matter (SOM), total nitrogen (STN) and total phosphorus (STP) were qualitatively and quantitatively analyzed along soil profile and treatment types. SOM and STN of all treatments exhibit an S-shaped curve within 2 m depth soil profile while STP follows a parabolic curve. N fixation ability of the three legumes seeded alone improves with increasing seeding density, and the Apparent Biological Nitrogen Fixation (ABNF) of M. sativa is 507.5 kg·hm^-2—the highest for the monoculture treatment. After a year of growth, A. adsurgens SOM averagely increases by 3.51%. Average STP output ratios of A. adsurgens and M. sativa are 43.14% and 40.24%, significantly higher than that of L. davurica (23.74%), and those of mixure of A. adsurgens and L. davurica, mixture of M. sativa and L. davurica, and mixture of A. adsurgens, M. sativa and L. davurica are 20.73%, 26.33% and 25.83% respectively. All the three legumes significantly enhance SOM. Though A. adsurgens and M. sativa consume much more STN and STP than L. davurica, they have a stronger nitrogen fixation ability. Utilization of soil resources by mixed legume community can be optimized by appropriate seeding density due to increased competition and symbiosis among the different species of the community.