苜蓿草地土壤氮素有效性的化学与生物测试方法比较

摘要：以半干旱区5龄和9龄紫花苜蓿(Medicago sativa cv.Longdong)土壤为供试对象，采用3种提取剂（0.01 mol/L CaCl2，热水和1 mol/L KCl）结合黑麦草(Lolium perenne)盆栽的生物测试对2个年龄苜蓿地土壤有效氮供应能力进行测定。结果表明，0.01 mol/L CaCl2提取剂对硝态氮的提取能力显著高于热水和1 mol/L KCl，1 mol/L KCl提取土壤铵态氮的提取能力最小；黑麦草在5龄和9龄苜蓿土壤中的吸氮量分别为2 100和3 100 mg/m2，由0.01 mol/L CaCl2、热水和1 mol/L KCl提取剂提取的土壤硝态氮含量与黑麦草吸氮量呈显著正相关关系，均可反映土壤供氮能力，0.01 mol/L CaCl2、热水和1 mol/L KCl提取剂提取的土壤铵态氮含量与植物吸氮量关系不确定，不能作为反映土壤供氮能力的指标。

Determination of soil nitrogen availability in alfalfa pasture by chemical and bioassay test

Abstract: The supply of soil available nitrogen in the 5 year and 9 year alfalfa pasture soils in a rainfed region was determined by three chemical extractants (0.01 mol/L CaCl2, hot water and 1 mol/L KCl) in combination with biological tests on ryegrass.This study showed that the CaCl2 extracted more NO3- N than hot water and KCl did. The extraction capacity of the three extractants for soil ammonium was hot water> 1 mol/L KCl> 0.01 mol/L CaCl2. N uptake by ryegrass in 5 year and 9 year alfalfa pasture soils was 2 100 mg/m2 and 3 100 mg/m2, respectively, and N uptake by ryegrass was a significantly positive correlation with the amount of NO3- N extracted by hot water, KCl and CaCl2, implying that the amounts of NO3- N extracted by hot water, KCl and CaCl2 was used to indicate the nitrogen supply of soil. However, the relationship between the amounts of NH4+ N extracted by hot water, KCl and CaCl2 and nitrogen uptake by plants is not certain, indicating that and the amounts of NH4+ N was not good indicator to describe the nitrogen supply of soil.