Effects Of The Long-Term Fertilization Practices On The Carbon, Nitrogen And Phosphorus Pools And Their Mobility

Analysis of the various forms of carbon, nitrogen, and phosphorus of a Huangnitu, a typical paddy soil in Tai Lake region, Jiangsu province, was conducted. The soil has been put into a scheme of long-term fertilization treatments for 13 years. The results are as follows:1. The contents of various forms of the carbon decreased from the soil surface to subsurface and affected by various fertilization treatments. The straw plus the chemical fertilizer the pig slurry manure plus the chemical fertilizer applications had enhanced the DOC in the soil 70.9% and 51.1%, the Cmic 25.3% and 28.9%, respectively. The soil DOC could be as a sensitive index of soil quality responding with the various agricultural practices.2. The soil respiration was the 1/3 as much as that of the nature soil in the same latitude. Only applying the chemical fertilizer was not good at the carbon sequestration.3. The main factors affected the CO2 discharge are the ratio of the soil carbon to nitrogen (C/N) and the soil aggregation. Soil aggregation could enhance the ability of the soil sequestrating the organic carbon.4. Long-term fertilization practices could change the ratio of the various forms of the soil nitrogen significantly, especially in the soil surface layer. Application of the chemical fertilizer plus the pig slurry manure had remarkably enhanced the content of the different forms of the soil nitrogen. Long-term fertilization practices could change the ration of C/N in the soil as well as the amounts of the soil microorganisms and their metabolism, so could affect the transformation of the soil N.5. Significant difference of the content of total soil phosphorous under continuous 13 years different fertilizer treatments was found. Chemical fertilizer plus the pig slurry manure could enhance the total soil phosphorous, resin-P and water-dissolved P significantly.6. The P loss varied with the different fertilization practices. As estimated from the total P pool values by mass balance principle, the soil had been subjected to water loss of P 2~8kg.hm-2.a-1. with that under chemical fertilizers only being the biggest. Therefore, P water loss in paddy soils might have active under continuous chemical fertilization alone in agriculture of this region and could not be accounted for by dissolution in water and subsequent runoff migration.