近20年太湖流域典型区土壤养分时空变化及驱动机理

长期的定位采样试验研究了近 2 0年锡山市甘露乡土壤表层 ( 0～ 2 0cm)中有机质、全氮、速效氮、速效磷、速效钾等土壤养分的时空变化趋势 ,并分析了土壤养分波动与国家政策、耕作方式、农业投入和单位面积农业纯收益之间的相互关系。结果表明 :2 0年间土壤养分质量总体上呈现先减后增的变化趋势。有机质呈现先减后增的变化趋势 ,且与耕作措施的改变有密切关系。全氮和速效氮呈持续上升趋势 ,上升幅度大于 1 0 0 % ,与氮肥使用量不断上升密切相关。速效磷、速效钾呈持续下降趋势 ,与磷肥、钾肥使用过少有关。国家政策和耕作方式、种植制度对SNQI影响十分明显 ,标准农业投入与土壤养分质量指数呈正相关关系 ,单位面积标准农业纯收益与土壤养分质量指数呈负相关关系

SPATIAL AND TEMPORAL CHANGES OF SOIL NUTRIENTS AND THEIR MECHANISM IN TYPICAL AREA OF TAIHU LAKE VALLEY DURING THE PAST TWO DECADES

The objectives of this study are to understand the law of spatial and temporal changes in soil nutrient quality in the Taihu Lake valley during in period of past two decades, and reveal relationship the change in soil nutrient and its driving forces at a regional level over a long time. A long term sampling experiment was conducted to analyze changes in soil organic matter, total N, available N, available P, and available K in Ganlu Township, Wuxi City. Results show as follows: (i) Soil or ganic matter decreased in the first decade, then increased during the next decade, which is assumed to be related with tillage methods; (ii) Soil total N and available N steadily increased by about 114.4% and 104.7%, respect ively, after 20 years, which is supposed to be associated with the in creasing of the rate of nitrogen fertilizers. At percent, the application rate of nitrogen fertilizers is about 646kg hm^-2 a^-1, which is far beyond the absorption capacity of the crop for growth; and (iii) Soil available P and available K decreased by about 52.3% and 24.2%, respectively, during the period. The content of available P and available K in the soil was only 5.1 mg kg^-1 and 44.8mg kg^-1, respect ively, which is lower than the demand of the crop for normal growth. These changes are believed to a result of inadequate fertilizer input. Only 87. 0kg hm^-12 and 80.4kg hm^-2 were used in 1999. In a word, soil nutrient quality index (SNQI) decreased from 1981 to 1986, then increased after 1986. The analysis of the relationship between the changes of SNQI and the socio-economic factors revealed: (i) The impacts of state policies and tillage methods, cultivating systems on SNQI are very obvious; (ii) Agricultural net input is positively correlated with SNQI (r= 0.832, p< 0.05); and (iii) agricultural net income per hectare is negatively correlated with SNQI(r= 0.915; p< 0.05). Therefore, we can repay the variation of soil nutrient quality of the past and forecast changes in SNQI in future by long-term socio-economic statistics.