| A two-year field experiment was conducted in Weibei rainfed highland of Shaanxi Province to evaluate the effects of different organic materials application on soil fertility characteristics and winter wheat yield. The experiment consisted of seven treatments: no fertilizer(CK), mineral fertilizers(T1), mineral fertilizers plus low amounts of maize straw(T2), mineral fertilizers plus medium amounts of maize straw(T3), mineral fertilizers plus high amounts of maize straw(T4), mineral fertilizers plus straw compost(T5), mineral fertilizers plus manure(T6). At the same time, a fertilizer application investigation combined with experiment was carried out to investigate the fertilization status of households in dryland area within Weibei rainfed area. The main results are as follows:1,A comprehensive evaluation was made on the effects of applying different organic materials on the soil chemical properties and enzyme activities in Weibei rainfed highland, based on field experiment and laboratory analysis. A total of ten quantitative indices were selected, and factor analysis and minimum Euclidean distance method were employed to evaluate the overall soil fertility. Crop yield was used to verify the evaluation results. Applying organic materials promoted soil fertility and crop yield significantly. Compared with applying chemical fertilizer alone, its combination with straw compost and with organic manure increased the wheat yield by 20.43% and 22.38%, respectively. The soil quality under the combined application of chemical fertilizer with straw compost was the highest, with an integrated score up to 56.53, followed by the combined application of chemical fertilizer with organic manure, and of chemical fertilizer with high amount straw. Therefore, a combined application of chemical fertilizer with straw compost or organic manure could improve the soil fertility significantly, and thereby, increase the crop yield. Using the selected 10 factors and factor analysis to evaluate the quality of soil fertility could accurately reflect the soil fertility level, and predict the soil productivity in the highland.2,The effect of different organic materials application on soil physical and chemical characteristics was studied through field experiments and laboratory analysis. Compared with T2 treatment, in terms of soil physical properties, soil bulk density under other organic fertilization treatments declined slightly, and it obtained the highest decrease (by 6.56%) in treatment with fertilizers input manure. The air-dried aggregate (>10 mm) content under T3,T5 and T6 treatment decreased compared to T2 treatment, and T3 treatment with the amplitude decrease(40.35%). In addition to T4 treatment, 5~3 mm aggregate content increased under the other four organic manure treatments, especially in T3 treatment. The >5 mm, 5~2 mm and 2~0.25 mm water-stable aggregate content increased from different levels under the organic fertilization treatments. It is increased to 6.49% under T5 treatment for >5 mm aggregate content; 5~2 mm aggregate content significantly increased by 77.98% and 2~0.25 mm aggregate content increased obviously under T6 treatment. Mean weight diameter (MWD) and geometric mean diameter (GMD) of dry-aggregates showed the following trend: T5>T4>T1> CK>T3>T6>T2, while the wet sieving results showed that the MWD and GMD under T3-T6 treatments were higher than T1 treatment. In terms of soil chemical properties, there were no significant differences with the organic matter content under T3-T6 treatments than T1 treatment. The total and available nutrient content showed the general increase. The soil cation exchange capacity increased significantly under each organic fertilization treatment compared to T1 treatment. There was no obvious influence on soil pH with each treatment except T4 treatment. Compared with T1 treatment, soil pH decreased distinctly under T4 treatment. The wheat yield under all treatments followed the order T5>T6>T4>T2>T3>T1>CK. The yield under T1 treatment was significantly higher than no fertilization treatment by 28.05%. T2-T6 treatments increased the yield significantly in the range of 5.72% to 12.58% compared with T1 treatment. There was obvious correlation between the soil nutrients and wheat yield, but soil organic matter and pH were not correlated with soil nutrients and wheat yield.3,The effect of different organic materials applied on soil microbiological properties such as soil microbial biomass and soil fertility was studied in Weibei rainfed highland soils through field experiments and laboratory analysis. The result showed that in different organic materials application treatments, the contents of SMBC changed between 156.84 mg·kg-1 to 452.95 mg·kg-1, and the contents of SMBN changed from 16.57 mg·kg-1 to 47.68 mg·kg-1. Compared with CK, T1 treatment increased soil microbial biomass C (SMBC) & N (SMBN), qMB, SMBC/SMBN, urease activity, invertase activity, alkaline phosphatase, soil organic matter(SOM), soil total nitrogen(STN), soil total phosphorus(STP) and CEC. The other organic materials fertilization treatments improved some soil microbial properties(SMBC & SMBN, qMB, urease activity, alkaline phosphatase, invertase activity) and increased some soil nutrients contents(STN,CEC,Available phosphorus,Available potassium) compared with T1 treatment. All these properties in the treatment of fertilizers with straw compost were the highest level. Meanwhile, some of soil microbial properties (SMBC, SMBN, urease activity and alkaline phosphatase) were positively correlated with soil nutrients. qMB was significantly correlated with STN, STP and CEC contents. The correlation between invertase activity and soil nutrients was not obvious.4,The crop yield,fertilizer application rate and other management measures in Heyang and Fuping in Weibei area were investigated in 2008. The main results showed that average N rate in winter wheat and spring maize was 154.9 and 148.6 kg·hm-2, the average P2O5 rate in winter wheat and spring maize was 87.7 and 31.7 kg·hm-2 and K2O rate in winter wheat and spring maize was 31.7 and 16.7 kg·hm-2 respectively. There existed big difference for wheat yield and fertilizer amount with different farmers. 45.6% of farmers applied excessive nitrogen, while only 4.8% of farmers applied organic manure. Fertilizer input on spring maize was not enough and the yield was low, average yield of maize was 272 kilograms per mu. The fertilizer species was single, the local farmers'fertilization habit and period were unreasonable. According to these situations, we will recommend reasonable fertilization method and suggest the departments help the farmers to know fertilization technology. |
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