| In dry farming area, crop rotation and fertilization is an important measure to improve grain yield, promote soil nutrient balance, and improve the utilization efficiency of water and fertilizer resources. Paper in view of the core problem that the loess plateau dry farmland soil fertility need to enhance, based on the long-term rotation and fertilization experiment, comprehensive compared and analysis the soil physical, nutrients and biological properties of top soil, discussed the influence of the long-term fertilization to various factors of soil fertility level. On this basis, it has carried on the numerical value of soil fertility evaluation through using fuzzy mathematics comprehensive evaluation method, and analyzed the various fertility factor contribution, according to the evaluation results analyzed the correlation of soil fertility and crop yield. The main conclusions are as follows:1. Crop long-term rotation and fertilization can improve soil compactness and soil aeration status. After 27 years of crop rotation, fallow soil compaction was tight(bulk density was 1.29 g·cm-3), alfalfa single application of phosphate fertilizer(density is 0.97 g·cm-3) and NPM(bulk density is 0.99 g·cm-3) of the soil were loose. Compared with fallow soil, soil porosity of alfalfa continuous M and NPM has increased 11.39% and 10.20% respectively. Soil porosity of wheat continuous M was higher 9.15% than fallow soil, grain-bean rotation NPM was higher 8.87% than fallow soil,grain-feed rotation NPM was higher 7.95% than fallow soil.2. Alfalfa continuous was more conducive to the accumulation of soil organic matter than other rotation system. NPM was more conducive to the accumulation of the soil organic matter than other fertilization treatment in different rotation systems. The soil organic matter of alfalfa continuous CK, P, NPM were 29.87 g·kg-1, 28.08 g·kg-1 and 41.04 g·kg-1 respectively, soil organic matter content of alfalfa continuous NPM was highest. The soil organic matter of wheat continuous NM and NPM were 20.37 g·kg-1 and 20.98 g·kg-1.Alfalfa continuous was more conducive to the accumulation of soil nitrogen than other rotation system. NPM was better than other fertilization to accumulation soil nitrogen in different rotation systems. The soil total nitrogen content of alfalfa continuous CK, P and NPM were 2.05 g·kg-1, 1.86 g·kg-1, 2.59g·kg-1 respectively. The soil available nitrogen content of alfalfa continuous CK, P and NPM were 129.27 mg·kg-1, 114.86 mg·kg-1, 163.34 mg·kg-1 respectively. The soil total nitrogen content of wheat continuous NM and NPM were 1.31 g·kg-1 and 1.40 g·kg-1 respectively. The soil available nitrogen content of wheat continuous NM and NPM were 75.13 mg·kg-1and 73.98 mg·kg-1 respectively.Under the same rotation mode, NPM is conducive to the accumulation of soil phosphorus when long-term rotation and fertilization. Phosphorus element fertilization effects of different rotation systems application NPM followed by alfalfa continuous > grain-bean rotation > grain-feed rotation > wheat continuous > corn continuous. The soil total phosphorus content of alfalfa continuous NPM was 1.13 g·kg-1, available phosphorus content was 68.14 mg·kg-1. The soil total phosphorus and available phosphorus content of wheat continuous were 1.03 g·kg-1 and 40.64 mg·kg-1 respectively. The soil total phosphorus and available phosphorus content of corn continuous were 0.92 g·kg-1 and 26.76 mg·kg-1 respectively. The soil total phosphorus and available phosphorus content of grain-bean were 1.07 g·kg-1 and 47.29 mg·kg-1 respectively. The soil total phosphorus and available phosphorus content of grain-feed were 1.03 g·kg-1 and 42.95 mg·kg-1 respectively.Soil available potassium content of any application of organic fertilizer treatments were higher, the soil available potassium content were reached the first level. Soil available potassium content of no applying organic fertilizer were low, the soil available potassium content were secondary or tertiary level. Rotation mode also affects the content of soil available potassium. Application conditions of NPM, soil available potassium content of alfalfa continuous and wheat continuous were higher than corn continuous, grain-bean rotation and grain-feed rotation. Soil available potassium content of alfalfa continuous NPM was 488.34 mg·kg-1. Soil available potassium content of wheat continuous M, PM, NM, NPM were 470.50 mg·kg-1, 309.58 mg·kg-1, 547.02 mg·kg-1, 500.53 mg·kg-1 respectively. Soil available potassium content of grain-bean NPM and grain-feed NPM were 301.82 mg·kg-1 and 427.61 mg·kg-1 respectively.3. Soil invertase, phosphatase and urease enzyme activity were sensitive response to crop rotation and fertilization measures. Alfalfa continuous was conducive to soil invertase, phosphatase, urease activity increase. Organic fertilizer was conducive to improving the phosphatase activity.4. Soil invertase activity, phosphatase activity, urease activity and catalase activity were with soil organic matter, total nitrogen and available nitrogen content was extremely significant linear correlation. Soil phosphatase activity and soil total phosphorus, available phosphorus and available potassium showed very significant linear correlation. Soil catalase activity and soil total phosphorus and available potassium content was significantly linear correlation. The correlation of soil invertase activity to soil available nitrogen content was the highest, correlation coefficient for 0.4462(P < 0.01). The correlation of soil phosphatase activity to available nitrogen content was the highest, correlation coefficient for 0.7228(P < 0.01). The correlation of soil urease activity to available nitrogen content was the highest, correlation coefficient for 0.6379(P < 0.01). The correlation of soil catalase activity to total nitrogen content was the highest, correlation coefficient for 0.3345(P < 0.01).5. Eight treatments of grain-grass 8 years rotation were significant difference in the number of soil bacteria, fungi, actinomycetes. Three treatments of grain-grass 3 years rotation were no significant difference in the number of soil bacteria, fungi, actinomycetes. Soil bacteria, fungi, actinomycetes number of rotation and fertilization system were generally higher than that of fallow soil. Soil fungi number of wheat continuous N and actinomycetes number of grain-grass rotation system in the potato crop were lower than that of fallow soil.6. Alfalfa continuous or organic manure application were benefit to fertilize soil. The IFI of alfalfa continuous CK, P, NPM were 71.35, 71.20, 87.87 respectively. IFI of wheat continuous, corn continuous, grain-grass 8 years rotation, grain-grass 3-year rotation, grain-bean rotation and grain-feed rotation were lower than 70.00.The effect of organic fertilizer and chemical fertilizer both on the soil could be better to fertilizer. The IFI of wheat continuous M, PM, NM, NPM were 55.15, 54.92, 60.62, 63.13 respectively. The IFI of wheat continuous CK, N, P, NP were 40.02, 39.65, 46.43, 47.46 respectively. |
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