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Sloping farmland is an important part of cultivated land resources in Yunnan district. The evaluation of cultivated-layer soil quality and the appropriate range of parameters for sloping farmland are the basis for the development of reasonable plough layer. Based on the Soil Management Assessment Framework (SMAF), taking the cultivated-layer soil quality of sloping farmland in Yunnan province as the research object, this paper constructed a soil quality index evaluation model (CLSQI) for sloping farmland, and used the minimum data set (MDS) method to screen the evaluation indicators to evaluate the soil quality of sloping farmland in Yunnan, proposed the range of soil parameters for rational tillage in sloping farmland. The results showed that the minimum data set (MDS) of soil quality evaluation of sloping farmland in Yunnan region consisted of five indicators: pH value, total nitrogen, total porosity, soil shear strength and slope. The comparative analysis of AL-CLSQI (the cultivated-layer soil quality index calculated by all indicators) and AL-CLSQI (the cultivated-layer soil quality index calculated by the minimum data set index) showed that the evaluation accuracy of cultivated-layer soil quality based on MDS index was higher. In the primary selection index system, the weights of soil bulk density, total porosity, capillary porosity, shear strength, and slope grade were larger, while in the MDS index system, the weight of the slope and total nitrogen content was larger. The cultivated-layer soil quality index (CLSQI) of sloping cultivated land was between 0.39 and 0.84, the mean value was 0.59±0.11, and the coefficient of variation was 0.19. The cultivated-layer soil quality of sloping farmland was generally “medium”, and it was generally low. The CLSQI of the sloping farmland in different sampling areas was significantly different (P<0.05), and the size relationship was: Chuxiong＞Shuangbai＞Xuanwei＞Ninger＞Malong＞ Shilin. The 0～20 cm sampling depth sloping farmland CLSQI (mean value 0.59) was greater than >20 cm (mean value 0.56), and the CLSQI (mean value 0.61) of purple soil sloping farmland was larger than the red soil (mean value 0.54) (P<0.05), while the ridge and contour farming cultivation mode sloping farmland CLSQI was larger than that of the straight-plowing. The order of the CLSQI of the sloping farmland in different agricultural divisions was: Northeastern Yunnan＞Central Yunnan ＞Southwest Yunnan. According to the corresponding relationship between the soil quality of the cultivated-layer and the crop productivity and membership function, the cultivated-layer was in a relatively reasonable state when the soil quality grade of the sloping farmland was at a “higher” and above level (CLSQI≥0.6). The appropriate range of MDS indicators for cultivated-layer of sloping land in Yunnan were indicated as follows: the pH value of 5.58～7.82, the total nitrogen content of ≥1.37 g/kg, the total porosity content of ≥52.28%, the soil shear strength value of ≥5.19 kPa, and slope value of ≤11.79°. The suitable range of the above-mentioned cultivated-layer soil parameters can be used as the standard for the rational cultivated-layer diagnosis of sloping farmland in Yunnan. The research can provide theoretical basis and parameter support for the quality evaluation of ploughed plough layer and the construction of reasonable plough layer. [ABSTRACT FROM AUTHOR]

Cultivated land being an essential natural resource, has been increasingly occupied in the last 60 years with the acceleration of urbanization. It is necessary to be careful in land use, in order to ensure food security and human existence. In addition, the quality degradation of cultivated land has seriously threatened to food security due to the misuse of land. Slope farmland, one type of cultivated land, is widely distributed in the plateau and mountain areas in the central and western China. Scientific quality evaluation of slope farmland is closely related to local food security and ecological environment, further to implement national protection schemes, such as the “Trinity” of quantity, quality and ecology. However, there are some features of slope farmland, such as wide distribution, large slope, soil erosion, frequent seasonal drought, low soil quality, to make accurate evaluation difficult. The evaluation index and model are also lacking. Taking the slope farmland in Yunnan as a research area, this study aims to construct a quality evaluation system of slope farmland based on the framework of “element demand regulation”. The 30 m × 30 m grid (pixel) was selected as an evaluation unit for the comprehensive weight. The quality of slope farmland was evaluated quantitatively, together with its characteristics of spatial distribution. The results showed that: 1) Index system of the Minimum Data Set (MDS) in quality evaluation of slope farmland consisted of 14 indexes, including the effective thickness of soil layer, arable layer thickness, bulk density of soil, soil texture, pH value of soil, organic matter, effective phosphorus, available potassium, accumulated temperature (≥10 ℃), field regularity, contiguity, amount of rainfall, assurance rate of irrigation, and field slope. 2) Slope farmland Integrated Fertility Index (SIFI) was distributed between 0.36 and 0.81, with an average value of 0.59. Most evaluation units of SIFI was less than 0.6, showing a significant difference (P<0.05). The SIFI size relationship between five types of soil in slope farmland were ranked in order: Lateritic red earths, Red earths, Purplish soils, Yellow earths, Yellow-brown earths. SIFI increased with the elevation in the range of 0-1 000 m, while decreased larger than 1 000 m, indicating the variation of SIFI was related to the range of elevation. 3) The quality of slope farmland can be Grade 6, 5, 7 and 4, according the national standard. Specifically, the quality of slope farmland was relatively high Grade 4 and 5 at the southern border, central, southeast, and western Yunnan, whereas, northeast and northwest Yunnan indicated low Grade 6 and 7. The Lorenz curve of quality grade showed a pattern of “S-type” distribution in different regions, indicating a low grade in Yunnan province. This finding can provide a scientific basis to improve the quality evaluation system of slope land, thereby to efficiently implement geological regulation of slope farmland. [ABSTRACT FROM AUTHOR]

Slope farmland is an important part of cultivated land resources in hilly areas of China. Identifying the spatio-temporal distribution and evolution characteristics of slope farmland resources is of great significance for rational planning and utilization of slope farmland resources and water and soil ecological environment construction. In this paper, using the land use data for 7 time points from 1980 to 2015, based on GIS spatial analysis technology, dynamic degree model, kemel density estimation and landscape pattern index model, the spatio-temporal distribution pattern and evolution law of slope farmland in Yunnan for nearly 35 years were quantitatively analyzed. The results showed that: 1) the area of slope farmland in Yunnan was 472.55×104 hm², accounting for 69.79% of the cultivated land area, and the average slope was 15.62°. The relationship between the area ratio of slope farmland in different agricultural divisions was: Southwestern Yunnan>Northeastern Yunnan>Northwestern Yunnan>Southern fringe>Western Yunnan> Southeastern Yunnan>Central Yunnan, and the average slope size relationship was: Northwestern Yunnan>Southwestern Yunnan>Northeastern Yunnan>Western Yunnan> Southern fringe >Southeastern Yunnan > Central Yunnan. 2) In the past 35 years, significant dynamic transfers had occurred in slope farmland, forest land, grassland and paddy fields, but the process of transfer in and out was generally balanced, and the area of slope farmland has a slight increase trend during the process of land use transfer. 3) The slope of most slope farmland was more than 8°, and the proportion of slope farmland with slope >15° was 78.54%. The area of slope farmland with different slopes in the past 35 years had a dynamic process. It showed an increasing trend for the slope farmland area with slope <15°, while decreasing trend for the slope farmland area with slope >15°. The area of slope farmland with different slopes has the dynamic process of “decreased→increased→decreased” or “decreased→increased→ decreased→increased”, and the fluctuation degree of >25° slope farmland was the largest. 4) With the evolution of spatio-temporal distribution of slope farmland in the past 35 years, the distribution characteristics of kemel density value in slope farmland have changed, but the change range was small. The distribution of slope farmland in most areas was in low-density value, and the area of high-density value was the smallest. Slope farmland distribution clusters were represented by four significant distribution zones: the Lincang distribution zone, the Lincang-Xishuangbanna distribution zone, the Pu’er distribution zone and the Zhaotong distribution zone. 5) Among the eight types of land use, the landscape dominance of slope farmland was in the middle position, and the fragmentation characteristics of slope farmland were the most significant among all land use types. In the past 35 years, the degree of fragmentation of slope farmland landscape has decreased, and the degree of contiguous use of slope farmland has been strengthened. The research results can provide theoretical support for the rational planning and utilization of sloping farmland and soil and water ecological environment protection in Yunnan. [ABSTRACT FROM AUTHOR]

Slope farmland is an important part of cultivated land resources in hilly areas of China. Identifying the spatio-temporal distribution and evolution characteristics of slope farmland resources is of great significance for rational planning and utilization of slope farmland resources and water and soil ecological environment construction. In this paper, using the land use data for 7 time points from 1980 to 2015, based on GIS spatial analysis technology, dynamic degree model, kemel density estimation and landscape pattern index model, the spatio-temporal distribution pattern and evolution law of slope farmland in Yunnan for nearly 35 years were quantitatively analyzed. The results showed that: 1) the area of slope farmland in Yunnan was 472.55×104 hm2, accounting for 69.79% of the cultivated land area, and the average slope was 15.62°. The relationship between the area ratio of slope farmland in different agricultural divisions was: Southwestern Yunnan>Northeastern Yunnan>Northwestern Yunnan>Southern fringe>Western Yunnan> Southeastern Yunnan>Central Yunnan, and the average slope size relationship was: Northwestern Yunnan>Southwestern Yunnan>Northeastern Yunnan>Western Yunnan> Southern fringe >Southeastern Yunnan > Central Yunnan. 2) In the past 35 years, significant dynamic transfers had occurred in slope farmland, forest land, grassland and paddy fields, but the process of transfer in and out was generally balanced, and the area of slope farmland has a slight increase trend during the process of land use transfer. 3) The slope of most slope farmland was more than 8°, and the proportion of slope farmland with slope >15° was 78.54%. The area of slope farmland with different slopes in the past 35 years had a dynamic process. It showed an increasing trend for the slope farmland area with slope <15°, while decreasing trend for the slope farmland area with slope >15°. The area of slope farmland with different slopes has the dynamic process of “decreased→increased→decreased” or “decreased→increased→ decreased→increased”, and the fluctuation degree of >25° slope farmland was the largest. 4) With the evolution of spatio-temporal distribution of slope farmland in the past 35 years, the distribution characteristics of kemel density value in slope farmland have changed, but the change range was small. The distribution of slope farmland in most areas was in low-density value, and the area of high-density value was the smallest. Slope farmland distribution clusters were represented by four significant distribution zones: the Lincang distribution zone, the Lincang-Xishuangbanna distribution zone, the Pu’er distribution zone and the Zhaotong distribution zone. 5) Among the eight types of land use, the landscape dominance of slope farmland was in the middle position, and the fragmentation characteristics of slope farmland were the most significant among all land use types. In the past 35 years, the degree of fragmentation of slope farmland landscape has decreased, and the degree of contiguous use of slope farmland has been strengthened. The research results can provide theoretical support for the rational planning and utilization of sloping farmland and soil and water ecological environment protection in Yunnan. [ABSTRACT FROM AUTHOR]