黄土丘陵区不同撂荒年限自然恢复的退化草地土壤养分及酶活性特征

Characteristics of Soil Enzymatic Activity and Nutrient of Pasture from Abandoned Field in Different Years on the Loess Hilly Areas

黄土丘陵区不同撂荒年限的自然恢复草地土壤中有机质、全N、有效N和速效P以及土壤蔗糖酶、脲酶、中性磷酸酶活性在剖面的分布均为上高下低，并随着土层的加深而降低。随着草地利用时间的增长，土壤有机质等养分和三种酶活性含量增高，活性增强。土壤养分及酶活性均以永久草地最高，三种酶活性与有机质和全N都呈明显的正相关，与有效N和速效P的相关不明显。人工草地不能增加土壤养分含量和酶活性，反而会大量消耗土壤养分使其肥力逐渐降低。

Contents of soil organic matter, total nitrogn, availabe N and P, sucrase, urease and neutral phosphatase in the pasture abandoned field during different years on loess hilly areas are all high in the upper layer of the profile and decrease with depth. With the increasing of years, soil organic nutrients and the three enzymatic activity are highest in permanent grassland and lowest in cultivated pasture.There is positive relationship between the activities of the three enzymes and organic matter and total N,and no distinctive relationship to available N and P. The cultivated pasture can not increase soil nutrients of enzymatic activities due to probably limited time and improper use of the pastrue.