Paddy Long-term Soil Fertility And Environmental Effects Under The No-tillage Ridge

The No-tillage and ridge culture is an effective measure for the simultaneous increase of soil productivity and eco-environmental quality, which is a core of sustainable development in agriculture. This paper deals with the evolvement of soil fertility in paddy soil and its eco-environmental effects under long-term No-tillage and ridge culture, conventional culture, and rotation of paddy and upland based on long-term experiment established in 1990. The research results are as follows: The matter circle or energy transformation distinguishes the ecosystem of paddy soil under long-term No-tillage and ridge culture from those under other culture systems. The No-tillage and ridge culture ultimately changes matter phase structure of soil surface in paddy field through remodel of micro-landform. The paddy soils under conventional culture are waterlogged, while soils in ridge are irrigated with capillary water. The spatial variability of water contents in paddy soils under No-tillage and ridge culture is bigger, and soil water moves upper ridge from lower ridge and two sides of ridge, and highly exchanges with environments. The No-tillage and ridge culture removes weakening of water layer on solar radiation. The soil thermal capacity under No-tillage and ridge culture decreases, while heat conductivity and thermal diffusivity increases, so the soils absorb much solar energy, and benefit transformation of soil matter. There was remarkable improvement of <0.01mm soil particle aggregation potentials and higher increments of organic microaggregate and Fe, Al-organic microaggregate after long-term No-tillage and ridge culture. The contents of mineral microaggregates and Ca, Mg-organic microaggregates markedly drop. The porosity and looseness was found in arrangement of soil microaggregates. The No-tillage and ridge culture descends gley horizon, and forms composite of soil horizon A-Pg-G-P that is one of basic characteristics of high-yield paddy soils. The organic matter contents of 0-40cm soil layer under No-tillage and ridge culture for 10 years significantly improve, and are 41.1%, 51.3% and 89.0% higher than those under conventional culture, rotation of paddy and upland, and before experiment separately. The contents of soil organic matter descend with depth of soil layers under various cultural systems. There is higher increment of soil loosely combined humic substances under long-term No-tillage and ridge culture for 10 years, and lower content of soil tightly combined humic substances as compared with other cultural systems. The light density of soil humic acid in wavelength 665mp and 445mjt under No-tillage and ridge culture are 0.122 and 0.705 respectively, and those under conventional culture are 0.062 and 0.321 separately. E4/E6 under No-tillage and ridge culture is higher than that under conventional culture. The results from infrared spectrum analysis on soil humic acid show that the increment value of enthalpy in top of heat release in DTA curve of soil humic acid under No-tillage and ridge culture is lower than under conventional culture. The adsorption maximum value of soil humic acid under conventional culture in 1000-050cm-is stronger than that under No-tillage and ridge culture. The oxidation stability coefficient, polycondensation degree, and arornaticity of soil humic substance under long-term No-tillage and ridge culture all are higher than those under conventional culture. The content of soil total N after long-term No-tillage and ridge culture is 9.7% and 26.7% higher than under conventional culture and rotation of paddy and upland separately. Th...