Agricultural Soil Nutrient Characteristics And Evaluation Of Five Counties In Qamdo District

The document about Qamdo soil was the result of second national soil survey research, which was focused on the research of soil classification, the distribution and soil basic properties, also analyzed the soil nutrients briefly.35 years had past and the status of land use in Qamdo had changed a lot, but the research on soil fertility in Qamdo after the second national soil survey was a blank.Therefore, the area agricultural soil pH value, organic matter, alkaline hydrolysis nitrogen, available phosphorus, available potassium, slow-release potassium (Fe, Mn, Cu, Zn) of five counties in Qamdo District were statistically analyzed and the overall nutrient characteristics and their impact factors were discussed. In order to reflect the the soil fertility basic characteristics of five counties in Qamdo District, its soil fertility was evaluated by using fuzzy comprehensive evaluation method and according to these characteristics, fertilizer recommendations were proposed for Qamdo Prefecture to provide the theoretical basis for land productivity improvement. The main conclusions were as follows:(1) The respect of soil pH, the size distribution of pH in the entire sequence of the five counties region was:acidic soil> neutral soil> alkaline soil, and Alkaline and neutral soil accounted for 98% of the total sample. The soil pH range in Mangkang County was 6.5～9.0, in Changdu County it was 6.3～8.6, in Dingqing County it was 6.7～8.6,in Zuogong County it was 5.9～8.6, in Luolong County it was 6.0～8.2.Longlong County soil pH mainly was concentrated in neutral range, While the rest four counties soil pH was concentrated in Weak alkaline range. The variation coefficient of pH value was 2.8%～6.5%, which was a weak variation.(2) New nutrient classification standard was applied to evaluate soil nutrient of five counties. The soil organic matter contents were relatively rich. The highest average organic matter content of soil was in Zuogong County, which was as high as 61.3 g/kg and the high level of ganic matter (>60 g/kg) samples were accounted for 52% of the total number of samples. In addition, from high to low the order was:Luolong County (46.3g/kg), Dingqing County (39.5g/kg), Changdu (38.8g/kg) and Mangkang County (37.5g/kg). In terms of alkaline hydrolysis nitrogen, the highest level of average soil alkaline hydrolysis nitrogen was in Mangkang County (251mg/kg), and the order of other four counties from high to low was:Zuogong County (233mg/kg), Changdu County (183mg/kg), Luolong County (176mg/kg) and Dingqing County (160mg/kg). The lowest level of average soil available phosphorus was in Changdu County (15mg/kg), and the order of other four Counties from low to high was:Luolong County (18mg/kg), Dingqing County (21mg/kg), Mangkang County (30mg/kg) and Zuogong County (38mg/kg). Compared with the second soil survey, the available soil phosphorus levels of five counties were improved, which was related to the application of phosphorus fertilizer. The order of Phosphorus deficiency(<10mg/kg) cultivated land ratio from high to low was:Dingqing (47%), Changdu (31%), Loulong (30%), Mangkang (18%), Zuogong (8%). The contents of available potassium and slow-release potassium were rich. The lowest level of average soil available potassium was in Luolong County (211mg/kg), and the order of other four counties from low to high was:Zuogong County (288mg/kg), Dingqing County (302mg/kg), Changdu County (346mg/kg) and Mangkang County (358mg/kg). In terms of slow-release potassium, the order of the five counties from low to high was:Mangkang County (591mg/kg), Dingqing County (632mg/kg),Zuogong County (643mg/kg), Changdu County (709mg/kg) and Luolong County (750mg/kg).The variation coefficient of available phosphorus was high, while the variation coefficient of organic matter, alkaline hydrolysis nitrogen, available potassium, slow-release potassium and trace elements was belonged to a medium variation, which might be related to zone natural factor in Qamdo such as the area terrain landform, climate, soil type and texture, etc.(3) According to the statistics of 500 soil samples, effective iron content of five counties was 75.2mg/kg, the soil samples whose iron content was in or below the critical value of iron deficiency accounted for about One-tenth of the total. Mn content was 53.1mg/kg and almost all samples had a Mn count that higher than deficient critical value. Effective zinc was 3.32mg/kg and soil available zinc content of most soil was very rich. The average content of available Cu was 2.19mg/kg and almost all was at a rich level. Effective boron content was 0.48mg/kg, which was belonging to a lack level and there were more than half of the soil whose boron was under critical value of 0.5mg/kg.(4) Soil organic matter and pH value were influenced by altitude. The organic matter of soil the soil pH increased as the altitude increased, while the soil pH decreased as the altitude increased. Soil alkaline hydrolysis nitrogen and available phosphorus were very significant positive correlation with soil organic matter, which showed that available soil phosphorus and alkaline hydrolysis nitrogen distributed consistent with organic matte. Soil mineralization rate had a significant negative correlation with available phosphorus and alkaline hydrolysis nitrogen content, while a significant positive correlation with organic matter, which showed that mineralization rate of soil organic matter and alkaline hydrolysis nitrogen and available phosphorus accumulation ability decreased as soil organic matter increased. Soil available potassium and trace elements had significantly positive correlation with organic matter, which meant that soil organic matter played a decisive role in conservation of soil available potassium and trace elements and to protect and maintain the natural vegetation could maintain soil fertility and had an important significance in production and ecological aspects in this area. Trace elements in soil (Fe, Mn, Cu, Zn, B) had significant negative correlation with soil pH value, indicating that soil pH value was a limiting factor to the effectiveness of soil trace elements and when the pH value reached to a certain value, the possibility of the lack of trace elements increased.(5) Six indicators (pH, organic matter, alkaline hydrolysis nitrogen content, available phosphorus, available potassium and slow-release potassium) were selected and the correlation coefficient method was applied to determine the weight of each nutrient factor and fuzzy comprehensive evaluation method was used for comprehensive evaluation of soil fertility in the study area.The result shouwed that:Soil fertility level of Qamdo five counties mostly was at a high level or above,and more than 4/5 of all soil was belonged to the range of 0.6～1.0. The order of five counties soil fertility from high to low was Zuogong County, Mangkang County, Changdu County and Luolong County and Dingqing County, and Zuogong County was belonged to level I, while Changdu County, Dingqing County, Luolong County and Mangkang County was belonged to level Ⅱ.