苜蓿草地土壤氮素有效性的化学与生物测试方法比较

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

以半干旱区5龄和9龄紫花苜蓿(Medicago sativacv.Longdong)土壤为供试对象,采用3种提取剂(0.01mol/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,1mol/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 100mg/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。

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.