镁碱化对土壤微生物活性和水解酶的影响

研究了镁碱度对土壤微生物生物量及其活性的影响,研究地点位于甘肃河西走廊疏勒河中游昌马洪积冲积扇缘。从10个具有不同镁碱化程度的采样点,采集土壤样品30个,测定了土样的pH、镁碱度、Mg2＋/Ca2＋、HCO3-＋CO32-、钠碱度、有机碳、全氮、微生物生物量碳、微生物熵、精氨酸氨化率、β-葡萄糖苷酶、磷酸酶、蛋白酶-casein、蛋白酶-BAA、脲酶等指标。结果表明：土壤pH和钠碱度没有明显的相关性,而和镁碱度、Mg2＋/Ca2＋、HCO3-＋CO32-显著正相关,相关系数分别为0.70、0.69和0.72。镁碱度和Mg2＋/Ca2＋显著正相关,相关系数为0.84。有机碳、全氮、微生物生物量碳、微生物熵、精氨酸氨化率的变化范围分别是6.4-18.5 g·kg-1、0.28-1.20 g·kg-1、23.1-351.9 mg·kg-1、0.37-2.52%、0.77-1.83μmol.g-1.d-1,和Mg2＋/Ca2＋之间显著负相关,相关系数分别是-0.52、-0.50、-0.59、-0.62、-0.65。β-葡萄糖苷酶、磷酸酶、蛋白酶-casein、蛋白酶-BAA、脲酶的变化范围分别是6.68-27.79μmol.g-1.h-1、7.03-25.99μmol.g-1.h-1、0.11-0.76μg.g-1.h-1、0.05-0.48μmol.g-1.h-1、0.07-0.61μmol.g-1.h-1吗,和微生物生物量碳之间显著正相关,相关系数分别是0.73、0.71、0.78、0.87、0.81,和Mg2＋/Ca2＋之间显著负相关,相关系数分别是-0.59、-0.58、-0.60、-0.56、-0.54。可见,镁碱化会造成土壤有机质含量下降、微生物生物量变小、微生物活性降低、水解酶活性低下,镁碱化是导致土地生产力低下的原因之一。

The effects of Mg2+alkalinity on soil microbial and hydrolase activities

The effects of Mg2＋ alkalinity on the size and activity of the soil microbial communities were investigated.Thirty soil samples were collected from 10 locations along the border area of the alluvial fan of Chang Ma of Shu Le He River in Hexi Corridor,Gansu Provinc.Soil pH,exchangeable Mg2＋ percentage,Mg2＋/Ca2＋,HCO3-＋CO32-,exchangeable Na＋ percentage,soil organic C,total N,microbial biomass C,microbial quotient,arginine ammonification rate,β-glucosidase phosphatase,protease-casein,protease-BAA,urease were determined and the effects of the soil chemical indices on soil microbial and biochemical activities were analysed.Data anslyses revealed that soil pH correlated positively with exchangeable Mg2＋ percentage,Mg2＋/Ca2＋ and HCO3-＋CO32-（r = 0.70,0.69,and 0.72,respectively）.Exchangeable Mg2＋ percentage had a close positive correlation with Mg2＋/ Ca2＋（r = 0.84）.Soil organic C,total N,microbial biomass C,microbial quotient,arginine ammonification rate were 6.4-18.5 g·kg-1,0.28-1.20 g·kg-1,23.1-351.9 mg·kg-1,0.37%-2.52%,0.77-1.83 μmol·g-1·d-1,respectively.These indices negatively correlated with Mg2＋/Ca2＋ and the correlation coefficients were -0.52,-0.50,-0.59,-0.62,-0.65,respectively.β-glucosidase,phosphatase,protease-casein,protease-BAA,urease were 6.68-27.79 μmol·g-1·h-1,7.03-25.99 μmol·g-1·h-1,0.11-0.76 μg·g-1·h-1,0.05-0.48 μmol·g-1·h-1,0.07-0.61 μmol·g-1·h-1,respectively.The hydrolases had a positive correlation with microbial biomass C,and the correlation coefficients were 0.73,0.71,0.78,0.87,0.81,respectively,but negatively correlated with Mg2＋/Ca2＋,and the correlation coefficients were -0.59,-0.58,-0.60,-0.56,-0.54,respectively.The results demonstrated that high Mg2＋ alkalinity resulted in low soil organic C,a small microbial community with low microbiological activity,low hydrolase activity,thus leading to low soil productivity.