EFFECT OF THIRTY YEARS INTENSIVE TILLAGE ON SPATIAL VARIATIONS OF SOIL NITROGEN AND PHOSPHORUS IN FREEZE-THAW AREA

摘要

Soil nitrogen and phosphorus are essential elements related to soil fertility, quality as well as soil productivity. However, for a freeze-thaw agricultural area with a large number of paddy fields, little information is known about spatial variation of soil nitrogen and phosphorus under intensive tillage and dramatic land-use change. 1981 and 2011, in this study, soil total nitrogen (STN) and total phosphorus (STP) in surface arable soils (0-20 cm) were examined in a seasonally frozen agricultural system, Northeast China. The results indicated that, after 30 years tillage, averaged STN content slightly decreased from 2.62 g kg~(-1) to 2.55 g kg~(-1), while mean STP values sharply declined from 1.31 g kg~(-1) to 0.84 g kg~(-1). With the model parameters that best fit the empirical semivariogram, spatial distribution maps of STN and STP were performed to explore their spatial variations. Content of STN have been noticeable reduced in dry land area whereas STP values decreased in the whole area, especially in sections with rice plants. When the study areas were separated into eastern and western parts, it was found that STN and STP values in both parts were almost equal in 1981 but showed significant difference after 30 years. Spatial distribution patterns of STN and STP in the study area have been significantly influenced by long-term intensive tillage. The findings provided information for precision agricultural management, better prevention of non-point source pollution and extended studies in similar regions.