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Soil Quality and Assessmentunder Different Landform and Land-use in Hilly and Gully Region of the Loess Plateau

Author: YueXiJie
Tutor: WangXuDong
School: Northwest University of Science and Technology
Course: Environmental Science
Keywords: loess plateau soil quality gis ahp farmland orchard
CLC: S158
Type: Master's thesis
Year: 2011
Downloads: 95
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Abstract


Changwu County is located in the northeast of Shannxi Province in the South of the loess plateau, situated between the east longitude 107°38’~107°58’, north latitude 34°59’~35°18’, there was the transition zone of conjunction that Weibei and Gansu Plateau. The elevation reaches as high as 1200m, Average annual rainfall was 584mm, mean annual temperature was 9.1 oC,frost-free period wad 171d,the climate type is humid continental warm temperate monsoon climate. There are three main types of land including the plateau, slope, gully. It was the region of severe soil and water loss. Before 1980, that mainly to grow food in this region, Then part of the farmland has turned into orchards, There occurred transformation of the conversion by Food-base to Food-Fruit base on the Loess Plateau, At present, this region has become an important production base of apple,but it is not clear that how did the soil quality evolved, so it is very necessary to carry on the appraisal to the local county territory soil quality condition, This relates the agricultural sustained development and the ecological environment change in Changwu County.This research take the Shanxi Province Changwu County as an example, has gathered the different terrain spots (plateau surface, land on slopes, floodland) and the different land utilization way (orchard and farmland) under soil sample, has studied fertility conditions and so on soil ulmin, major elements and trace element, screening had determined the soil quality rating’s indicator system, has established the smallest data set, under the GIS platform support, the application improvement analytic hierarchy process determination evaluating indicator’s weight, establishes the soil quality scale, constructs the Changwu County soil quality distribution map, knows the Changwu County soil quality condition comprehensively, to instruct the local agricultural production to provide the theory basis, is advantageous for the soil ecosystem to develop toward the positive cycle direction. The main results were as follow:1 The SOM content is 5.16g/kg~18.25g/kg in the area of Changwu County, the average content is 12.57g/kg.The content of SOM has achieved the medium fertility level of this area. The content to be different levels of soil organic matter and soil active organic matter in different landform.The plateauland(12.39g/kg)was relatively higher than the floodland(11g/kg) and the slopingland(12.05 g/kg),also the different Land-use affects the content change of SOM and SAM.The content of SAM and SOM among the floodland and the sloping, the plateauland existence significance difference. Using the way under the orchard soil, SAM to be slightly higher than differently the farmland soil, the orchard surface layer is higher than the lower level; The tendency which the orchard surface layer soil after the age increases presents increases progressively first decreases progressively, the tendency which similarly, the orchard surface layer soil after the age increases presents similarly increases progressively first decreases progressively. As the overall tendency, the organic matter and SAM to present the north and south high, middle the low tendency, is somewhat low along the Jing River basin.2 The TN content of this area ranges from 0.28g/kg to1.37g/kg,the overall average was 0.89g/kg . the average content of AN was 59.68mg/kg.Soil total nitrogen achieves the medium fertility level of the whole areas. The orchard soil total nitrogen achieves the higher fertility level, the farmland reaches on the medium level. The different terrain spot to TN, AN’s influence also slightly has the difference, the plateau TN (0.94 g/kg)、AN (64.15 mg/kg) and the floodland (0.85 g/kg, 49.85 mg/kg), the slopingland (0.82 g/kg, 59.68 mg/kg) is relatively higher; The TN and AN under the orchard surface layer relatively is differently higher than the farmland; Along with the increase of orchard’s age, in 5~15 the orchard soil mantle TN, AN had increased. As the overall tendency, the soil entire nitrogen high spot mainly concentrates north and northwest of Changwu County.3 The overall average contenr of TP、AP as 0.67g/kg, 17.55mg/kg.The AP reached on the middle fertility levels. The AP of orchard achieved high fertility soils, the farmland in general reached to the middle soil fertility level; Under different landforms, the TP and AP content of plateauland were higher than the floodland and slopes. The different Land-use patterns, the TP content of upper orchard was slightly higher than the farmland, the AP content of upper orchard was higher than the farmland more than twice as high.With the increase of years of orchards, the TP and AP content occurred the cumulative effect in the upper and lower layer, that was reached maximum content on 5-15 years of the orchard.4 The area of soil potassium changes in 16.68g/kg~28.10g/kg,the overall average was 22.23g/kg, The area of soil AK changes from 63.13 mg/kg to 513.13mg/kg,average content of AK was 199.36mg/kg, the AK in the region reached a high fertility levels (>150mg/kg). The AK content of orchard and farmland have reached higher levels;The TK in different positions did not have significant differences, the TK of orchard and farmland soil were significantly higher.The AK content of orchard were slightly higher than the farmland (increased 29.4%). With the increase of years of orchard planting, The AK content was gradual increase in surface of orchard, The AK content of 15 years、5-15 years compared with <5 years increased by 35.6%, 42.3%, The AK was increased more in the prosperous period.5 The overall average content of trace element in soil, Fe: 2.73mg/kg, Mn: 19.20 mg/kg, Cu: 0.76mg/kg, Zn: 0.68mg/kg,The Mn achieves the higher fertility level. Landform influenced the distribution of soil trace element.The content of soil trace element(Fe、Mn、Cu)shows trends that plateauland> slopingland>floodland. However,Zn has relatively high level in floodland.Under the different land-use, the trace element average content of orchard was higher than the farmland, The different land-use have the significance difference differently. Along with increase of planting age, The soil trace element presents the cumulative effection in the upper and lower layer of orchard(5-15years).6 Selected soil physical and chemical properties and soil enzyme activity was taken as evaluating indicators which was closely related to soil quality, such as soil organic (SOM) matter, total N, and cation exchange capacity (CEC). The paper has bettered the traditional analytic hierarchy process (AHP) and put forword to a new exponent scale for estabilishing comparison matrix, determining the weight values for each evaluating indicator, and comprehensive indexing method of fuzzy mathematics was adopted to calculate the soil quality index. The results indicated that effctive hierarchical analysis structure, avoiding the process of consistency test to the comparison matrix, could be estabilished when the bettered exponent scale was applied to level analysis model. AHP model made the discrimination of weight values of evaluating indicator more obviously compared to partial correlation coefficient model, therefore, AHP can avoid equalization trend of weight values. According to variance-test to soil quality index which two models obtained result shown that they existed significant differences between two models. Evaluation results indicated that difference between topographic position resulted in the difference of soil quality and not well-distributed in Chang Wu County.while medium level accounted for 75.2%,and about 17.9% of the state of soil quality is poor.7 Results were basically consistent with local conditions according to field-survey analysis.Based on the platform of GIS that divided and mapped the grade distribution of soil quality of Chang Wu County, achieved the visualization of county-scale soil quality and had a clear understanding on the whole county-scale soil quality. Results indicated that soil quality of orchard is better than farmland on the same topography site and soil quality in the different topography positions are in the order of table-land>bottom-land>slope-land. Throughout the county scale, the distribution of soil quality indexes between 0.195 to 0.710 andⅢ、Ⅳ、Ⅴgrades are only 27% of the entire area, however,Ⅱgrade was accounted for 59.7% of the entire area. On the whole, the soil quality of the research region at a medium level and affected by topography site largely, however, the soil quality of orchard is better than farmland.

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CLC: > Agricultural Sciences > Agriculture as the foundation of science > Soil > Soil fertility (soil fertility )
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