Abstract:

The study aims to clarify the comprehensive soil fertility index and soil nutrient characteristics in Gangcha County, so as to lay the foundation for improving the quality of arable land according to local conditions, improving soil fertilizer utilization rate of arable land in Gangcha County, applying fertilizer rationally and realizing precision agriculture. The soil fertility of arable land in Gangcha County, Qinghai Province was studied, and 19 indices were measured by field sampling and soil sample testing according to the current valid standards such as NY/T 1121. Principal component analysis and hierarchical analysis were combined, and the fuzzy integrated evaluation method was applied to evaluate the fertility of arable soils. The results showed that the soil fertility level of arable land in Gangcha County was divided into 5 levels, among which the proportion of arable land evaluated as level 1-3 was 3.45%, 24.46% and 18.95%, respectively, the level 4 was 46.60%, and the level 5 was 6.55%. Among the massive elements, the average values of eight indicators (organic matter, available nitrogen, available phosphorus, available potassium, slowly available potassium, total nitrogen, total phosphorus and total potassium) were 25.19 g/kg, 99.85 mg/kg, 13.69 mg/kg, 47.87 mg/kg, 717.82 mg/kg, 1.97 g/kg, 1.09 g/kg, and 22.22 g/kg. The average values of the eight indicators (effective molybdenum, effective sulfur, effective silicon, effective iron, effective manganese, effective boron, effective zinc and effective copper) in the medium and trace elements were 0.03, 45.21, 99.09, 5.52, 2.00, 0.59, 0.58 and 0.88 mg/kg. The proportion of arable land evaluated as grade 4 was the highest, the arable land evaluated as grade 1-3 was mainly distributed in Hargai Town, the grade 4 was mainly distributed in Qinghai Lake Farm; the grade 5 accounted for more in Huangyuquan Farm and Yikeulan Township. The average values of organic matter, available nitrogen, available potassium, total nitrogen, total phosphorus, effective iron and effective molybdenum were higher in the arable land evaluated as grade 1, the average value of total potassium was higher in the grade 2, the average value of effective zinc content was higher in the grade 3, the average value of available phosphorus, effective molybdenum, effective boron and effective copper content were higher in the grade 4, the average value of slowly available potassium, effective sulfur and effective silicon content were higher in the grade 5.

Key words: principal component analysis, cluster analysis, comprehensive evaluation of soil fertility, arable soil, Gangcha County