长期施肥对灰漠土生物群落和酶活性的影响

长期定位试验表明:施肥对灰漠土生物类群、酶活性有一定影响,同时生物类群和酶活性也改变了土壤生态环境.(1) 施肥对灰漠土动物个体及类群数的影响显著,长期单施化肥对土壤动物优势度作用较大,化肥配施有机肥丰富了土壤动物组成,化肥配施秸秆有利于增加土壤动物的丰度,尤其是疣跳科和等节跳科动物个体数量增加近10倍,长期不施肥土壤动物均匀性较高,但优势类群数较低;(2)灰漠土微生物组成以细菌为主,特殊微生物生理类群是以固氮菌和氨化细菌数量居多.长期单施化肥不利于土壤微生物生长,几种菌类数量均较低,化肥配施有机物料增加了土壤微生物类群数量,比对照增加15%～44%,长期不施肥土壤微生物数量高于单施化肥处理.(3) 灰漠土自身过氧化氢酶含量较高,蔗糖酶次之.土壤4种酶活性中除过氧化氢酶与土壤养分之间呈负相关以外,其余3种酶活性与土壤速效养分均呈正相关或显著正相关.长期单施化肥土壤脲酶、磷酸酶活性降低,长期不施肥土壤脲酶、磷酸酶活性高于单施化肥处理,化肥配施有机肥或秸秆的土壤脲酶、蔗糖酶、磷酸酶活性比长期不施肥增加了24%～31%.因此,化肥配施有机物料增加了土壤酶活性,加速了土壤熟化,改变了土壤生态环境.

Effects of long-term fertilization on biodiversity and enzyme activity in grey desert soil

Long-term field experiments were conducted to examine the effects of long-term fertilization on biodiversity, enzyme activity, and ecological environment of grey desert soil, The obtained results are summarized as follows. (1)Fertilization had a significant effect on the number and community of soil animals. Long-term application of chemical fertilizers considerably affected soil animal Simpson index. Chemical fertilizer in combination with organic fertilizer increased soil animal diversity. Chemical fertilizer plus straw increased the abundance of soil animals, especially neanuridae and isotomidae, which increased in number by approximately 10 times. Animal uniformity was higher, but preponderant community was smaller in the long-term control plot (withoutfertilization). (2)Bacteria were thedominant community of microorganisms in the grey desert soil, whereas zotobacter and ammonifying bacteria dominated the special microbial physiological communities. Long-term application of chemical fertilizers alone inhibited the growth of soil microorganisms, as evidenced by the decreased number of several microbes. Chemical fertilizer with organic material increased soil microbial biomassby 15%-44%, as compared with the control. The number of microorganisms in control plot was greater than that of chemical fertilizer treatment plot. (3) Catalase activity was higher in grey desert soil, and that of invertase was relatively low. Available nutrient contents in the soil showed a negative relationship with catalase activity, but positively correlated with activities of the other three enzymes. Long-term applicaiton of chemical fertilizer alone reduced urease and invertase activity in the soil. Urease and phosphatase activities in the control plot were higher than that of chemical fertilizer only treatment. When chemical fertilizer was applied together with organic material,the activities ofurease, inverase, and phosphatase increased by 24%-31%as compared to the control. Therefore, chemical fertilizer in combination with organic material should be recommended for improving biodiversity, enzyme activities and subsequent soil quality of the desert soil.