The Soil Fertility Character In The Hilly Area Of The Central Sichuan Basin

The hilly area of the central Sichuan basin is an important procreative area of agricultureof China. The Neijiang city lies in the southwest part of the hilly area of the central Sichuanbasin, the typical of hilly region physiognomy. This area is overpopulated and everyone hassmall number of the cultivated land resource. And the landform was crashed and there wasmuch crumb in soil parent material, additionally it has been affected by human disturbance,those instance resulted in many problems such as the drop of soil fertility quality, the declineof agricultural production, the worsen of environment quality and so on. This essay takesNeijiang city in the hilly area of the central Sichuan basin as the research area, selectingeight hillock according to the practical geographical feature, soil sampling accorded to foursoil parent materials, namely, J₃s, J₂z, J₃P and J₂s, combining the ways of land use (cultivatedland, forestland and grassland), dividing the slope of hillock into three parts: peak slope,middle slope and foot slope, and selecting soil sampling in each slope location (slopedirection was same). With the analysis of physicochemical properties of soil and varianceand correlation, the main results of study are as follows:(1) The soil physicochemical properties which are developed from four soil parents (J₃s,J₂z, J₃P and J₂s) are different in various degrees. The results indicates that, the content of siltparticle and sand particle is higher in soil developed from J₂s than soil developed from theothers. The ratio of the content of soil clay to the content of soil sand in J₂s, aggregatecontent of soil clay content in J₂s and soil bulk densities of J₂s is also lower than the soildeveloped from the other parents. In the different soil parent material, the content of the soilorganic carbon, readily oxidation carbon, total nitrogen, available potassium varies the same:J₃s＞J₃p＞J₂z＞J₂s. The ANOVA analysis shows that soil parent material has remarkableinfluence on the content of total phosphorus, total potash, available potassium and CEC.(2) Soil physicochemical properties exist distinctly in the different slope location. On thedifferent hillock slopes, the content of soil mucilaginous grain gradually increases, soiltexture is heavier and heavier, and the soil aggregation rate gradually rises, but the soildisperse coefficient gradually reduces. The analysis of soil nutrient characters on differentslopes shows that most of the content of nutrient is declining with the soil slope increasing.Because of scouring, eluviations and other effect in the middle and top of hillock, manysuperficial nutrients are lost and accumulated on the foot of slope. However, the content ofsoil total phosphorus and soil total potassium on the middle of hillock is higher than that onthe top of hillock with the influence of the microtopography.(3) Affected with different ways of land use of hillock in the hilly area of the central Sichuan basin, soil physicochemical properties also differ in various degree. The content ofsoil mucilaginous grain and the ratio of the content of soil clay to the content of soil sand inforestland are higher than that in cultivated land and in grassland. But the soil bulk densitiesof forestland are lower than that of grassland and cultivated land. Because of the effects thatforest crop root system and forest floor take, the soil physical properties of forest plantationare far better. The content of soil organic carbon(9.46g/kg), readily oxidationcarbon(2.14g/kg), total nitrogen(0.48g/kg), alkali hydrolysable nitrogen(35.43mg/kg),available potassium(271.47mg/kg) in forestland is higher than that in grassland andcultivated land. The content of soil available phosphorus(7.13mg/kg) and totalpotassium(37.82g/kg) in cultivated land is higher than that of in forestland and grassland.The content of soil total phosphorus(2.03g/kg) and CEC (30.28cmol/kg)in grassland ishigher than that in cultivated land and forestland. The analysis of the soil physicochemicalproperties in different ways of land use of hillock shows that, the content of soil nutrient andphysical properties depends on the variations between land use and cover, and humanactivities is the main factor influencing the variations.(4) Significant correlations are revealed between soil physical properties and soilchemical properties. The content of clay particle with all physical indicators is significantpositive correlation. That shows that the clay particle is the centre of soil activity in the hillyarea of the central Sichuan basin. Significant correlations are found among all chemicalindicators except for soil total phosphorus and available phosphorus. The 10 chemicalindicators with the composition of soil particles are significant positive correlation, and thosewith the content of sand particles are significant basically negative correlation. The result oflinear fitting shows that the influence of readily oxidation carbon on the soil organic carbon,the influence of the soil organic carbon on the soil total nitrogen and the influence of the soiltotal nitrogen on the soil alkali hydrolysable nitrogen are all observable.The hilly area of the central Sichuan basin area has long been encountered with suchproblems as the soil erosion and soil loss caused by human disturbance and distruction. Inorder that sustainable use of soil resource can be realized, measures should be taken toimprove the soil fertility, such as strengthening the management of the slope plough soil,conversing cropland to forest and grassland, building terraced fields and so on.