| Based on 6 types of farmlands with 13~38 years of tillage in Ulanbuh oasis area, 24 indicators in 0-20cm soil layer were tested, and the integrated quantitative assessment and evolution of soil quality were done by factor analysis method and principle of fuzzy mathematics. The results showed that 17 indicators were screened.The 17 indicators inculded organic matter, available N, available P, total K, available K, readily available K, pH, CEC, fungus, actinomyces, invertase, urease, alkaline phosphatase, protease, cellulose, physical clay and microaggregate, which could explain 85.2% of variation information to SQI (Soil Quality Index). the evaluation results were highly representative and verifiable, and the simulation equation was established between SQIs and 17 indexes. SQIs ranging from 0.20 to 0.62 were significant difference. SQIs of all farmlands were 1.5~2.2 times higher than that of control samples on average, soil quality was improved as a whole. The proportion of SQIs<0.5 was 83%, SQIs were lower wholly (mean value 0.41). SQIs showed very significant evolutionary trends toward increase at first,and then slight decrease over nearly 40 years of farming, the critical time was in year 30, however, SQIs was higher than that of farmlands cultivated for 13 years overall after 38 years of farming. It was recommended to adopt balanced fertilization such as organic fertilizer or organic fertilizer + NP + small amount of supplement K, according to actuality of study area, nitrogen fixation forage grass should be planted to fallow and improve farmlands further. |
