Red Soil Quality Characteristics And Fertility Ameliorating Measures In Central-south Hunan Province

Soil degradation was a descensive process about its physical, chemical and biological properties and productivity because of adverse natural conditions and unreasonable soil tillage and use by human. In order to clarify soil degradation status of erode degraded red soil region in Hunan province, this paper analyzed soil genesis and development and soil taxonomy, spatial variability of soil nutrients and soil quality evaluation on different land use. Further more, some soil illuvial layer were collected to simulate erode degraded red soil, and two pot experiment were designed to analyze the effects of different fertilization on fertility of erode degraded red soil, some fertility ameliorating measures were proposed for erode degraded red soil who developed from different parent material. The main results were summarized as follows.1. The main soil texture in erode degraded red soil region was clay, the low altitude soil was more viscid than high altitude soil, the soil texture of surface soil layer is loam, the soil profile is more deeper, the soil texture was more viscid. The clay content of surface soil layer and Half-weathered parent material layer was lower than illuvial soil layer, but the clay content of few surface soil layer was high. There was a stronger viscid process in illuvial soil layer because of high clay content, and its clay content leached significantly. The attitude of soil profile was all low, the highest attiude was 165.2m. The weathering of low attitude soil was stronger than high attitude soil, so the character of soil profile in erode degraded red soil region was high free degree of iron oxide, low activity of iron oxide, low hydration coefficient of iron oxide, low organic mater accumulation, and CEC7<24 cmol(+)/kg, the soil profile was in the process of moderate iron-accumulation, but pH value was different from various soil parent material. There were 8 soil subgroup including Typic Hi-weatheri-Udic Ferrosols, Plinthic Hapli-Udic Ferrosols, Typic Fe-accumuli-Stagnic Anthrosols, Mottlic Fimi-Orthic Anthrosols, Dystric Purpli-Orthic Primosols, Typic Udi-Orthic Primosols, Typic Carbonati-Udic Cambosols, Mottlic Purpli-Udic Cambosols respectively.2. Spatial variability of soil nutrients had affected by structural factors(such as topographic, parent material) and random factors(such as fertilization, land use type, vegetation). Using the method of GIS and Geostatistic, we carried on semi-variance analysis and kriging interpolation to the nutrient data and grades, so we obtained the spatial variation chart which could well reflect the spatial variation information of soil nutrient. The results showed that the variable coefficients of all type nutrients were in the range of 19.57%-61.50% in red soil region, belong to medium variance. the variable coefficients of nutrients were in the range of 5.66%-65.46% in purple soil region, soil organic mater, available N, available P, available K, total N and total K belong to medium variance, soil total P and pH value belong to weak variance.In red soil region, the distribution of soil available N, available P, total N, total P, pH value and organic mater were closely related with parent material, its were higher in north region which developed from limestone parent material, and lower in south region which developed from quaternary red earth and slate parent material. The distribution of soil available P was also related with land use type, there were more paddy soil in north region, so soil available P content was increased distinctly by paddy rice-upland crop rotation. The distribution of soil available K were closely related with parent material, landform and fertilization habit, its was higher in west region which developed from quaternary red earth parent material, and lower in northeast region which developed from limestone parent material. Futher more, there was more upland in west region, the loss of soil available K was lower than paddy soil. The distribution of soil total K was closely related with parent material, its was higher in north and southeast region which developed from limestone and slate parent material respectively, and lower in west region which developed from quaternary red earth parent material.The soil pH value was about 7 because of purple sandshale parent mater in purple soil region, the distribution of soil nutrients were closely related with land use type and fertilization habit. The content of soil available K and pH value were higher in east which had more upland, and lower in west which had more paddy soil. The content of soil available N, available P, total K and organic mater were higher in west which had more paddy soil, and lower in east which had more upland.3. The results of evaluating on the soil fertility quality by use of the Fuzzy comprehensive assessment under different types of land use showed:soil pH is nearly acidity; total N, available N, total K and available K content were medium on, but organic mater, total P and available N were not rich. The soil fertility quality of paddy soil belong the high level, upland belong the medium level and wasteland belong the low level.4. Soil ameliorant was a new soil restoration for erode degraded red soil made by institute of environment and sustainable development in Chinese academy of agriculture science. The results of 3 years pot experiment showed:applying soil ameliorant II and organic fertilizer could increasing content of available N,P,K and organic mater compared with appling chemical fertilizer, and also it could promoting the use efficiency of soybean and rape for fertilizer N, P and K, and increasing the biomass of soybean and rape. Especially applying organic fertilizer could increasing the microbial activity and applying soil ameliorantâ…¡could alleviating soil acidification and increasing the number of microbe such as bacteria, fungi, actinomycetes and so on.The available P and available K content of quaternary red clay was higher than granite and slate, and its had strong resistance to acidification, so quaternary red clay had better restorable potential, but the organic mater content of variegated horizon red soil was lower than homogeneous horizon red soil, and the improved effect of available P and available K for variegated horizon red soil was better than homogeneous horizon red soil by ameliorantâ…¡. In rape cultivation period, there had evidently improved effect for available P on slate red soil by organic mater treatment. There also had high use efficiency of soybean and rape for fertilizer N, P and K and high biomass on slate red soil, so slate red soil had good restorable potential. There had evidently improved effect for available N and available P on granite red soil by fertilizer treatment, but the use efficiency of soybean and rape for fertilizer K was lower because of lower available K on granite red soil, and the biomass was also lower, so the fertilizer K should be incresed on slate and granite red soil.