What are the reasons for the nutrient changes of paddy soil in Duyao Town, dongzhi county?

The reason for the change of soil nutrients in rice is 1. Human factors. At present, a large number of young people in rural areas go out to work, unable to take into account the time-consuming and laborious accumulation and application of organic fertilizer. The application of organic fertilizer in paddy soil is limited, and the increase of organic matter content is not significant, which leads to the deterioration of soil physical properties, the decline of soil suitability, the decline of water and fertilizer conservation ability and the decline of natural disaster resistance.

However, with the extensive use of high-concentration phosphorus-containing compound fertilizer, the phosphorus content in paddy soil has been greatly improved, but the input of potassium is relatively insufficient. The improvement of potassium mainly depends on the application of compound fertilizer or compound fertilizer. For some farmers who use simple fertilizers, nitrogen fertilizer, phosphorus fertilizer and light potassium fertilizer are often emphasized, which makes the increase of soil potassium limited and obviously lower than phosphorus on the whole.

2. The use of rice fertilizer has increased. According to statistics, from 1982 to 2020, the average rice yield in Duyao Town will increase from 5652kg/hm2 to 6405? Kg/hm2, increased by 65438 03.3%. The pure amount of chemical fertilizer increased from 189. 15kg/hm2 to 345kg/hm2, with an increase of 82.4%, indicating that the increase of rice yield in Duyao Town mainly depends on the increase of chemical fertilizer consumption besides varieties and other factors. A large number of chemical fertilizers not only increased the yield, but also promoted the improvement of soil fertility level and nitrogen, phosphorus and potassium nutrient content.

3. The amount of nitrogen and phosphorus fertilizer is large, and the amount of potassium fertilizer is small. The net amount of nitrogen, phosphorus and potassium in 1982 paddy field was 90.0, 22.5 and 16.5 respectively? Kg/hm2, and the ratio of them is1:0.25: 0.18; In 20 15 years, the pure amounts of nitrogen, phosphorus and potassium are 15 1.50, 45.75 and 9 1.95, respectively? Kg/hm2, the ratio of the three is1:0.3: 0.6; The contents of nitrogen, phosphorus and potassium are 1.68, 2.03 and 557 times respectively. Because of the different bases, the amount of nitrogen and phosphorus fertilizer has exceeded the needs of rice growth, while the absolute amount of potassium has remained at a low level.

4. Blind fertilization, unbalanced nutrient input and low fertilizer utilization rate. In rice fertilization, there is a common phenomenon of blind fertilization, or partial application of nitrogen and phosphorus fertilizers, or unreasonable fertilization methods, and the technology of deep application of nitrogen fertilizer has not been widely promoted. The unreasonable ratio of nitrogen, phosphorus and potassium, the decline of fertility and the low utilization rate of fertilizer are not conducive to the improvement of rice yield and quality. After years of application of phosphate fertilizer, the accumulation of phosphorus in soil is obvious, and the content of available phosphorus generally increases, which significantly reduces the benefit of applying phosphate fertilizer. Although the seasonal utilization rate of phosphate fertilizer is low, generally only 10%~25%, its residual effect is very long. According to some data, the cumulative utilization rate of residual phosphorus fertilizer reached 38.9% within 20 years, which was almost equivalent to 40% of the utilization rate of constant nitrogen fertilizer.

Therefore, the old concept of "low utilization rate of phosphate fertilizer" should be completely changed, and the ratio of nitrogen to phosphorus should be maintained at 1:0.3 according to the results of soil testing.

5. Lack of deep ploughing and deep ploughing, shallow plough layer. In some rice planting areas in Duyao Town, rotary cultivators are used to crush fields, and some farmers pursue interests unilaterally. In order to save oil consumption and mechanical wear, the tail wheel is raised, which leads to the gradual thinning of the plough layer, generally below 15cm or shallower, with poor water and fertilizer retention capacity and reduced soil permeability.