Soil nutrients are the main source of crop nutrition and the material basis for crop growth and development. The important indicators of soil nutrients include soil organic matter, total nitrogen, available phosphorus, and available potassium. The content of these nutrients depends on the parent material and is influenced by human fertilization. Over the years, due to long-term large-scale fertilization of soil, the yield of crops has gradually increased. With the changes in cropping systems, soil nutrients have undergone great changes. From the perspective of economical use of chemical fertilizers, it is often desirable to understand the effects of soil productivity levels and soil nutrient levels on the effects of fertilization. It is customary to assume that low-productivity soils and soils with low nutrient content have a high yield and therefore have an increased yield. Therefore, higher productivity and higher nutrient content soils are considered to have low yield-increasing effects. Therefore, it is necessary to reduce the amount of fertilizers. However, the level of crop yield and the effect of fertilization are often affected by climatic conditions, cultivation conditions, and crop varieties, so it is difficult to see the above-mentioned relationship. The near-neutrality of soil pH is one of the necessary conditions for ensuring high maize yield. Solid soil and solar-up soil are factors that inhibit production due to high soil pH. The level of available phosphorus content of soil and the rank of maize yield were exactly the same, indicating that soil available phosphorus content is a major factor in the production level. Although the content of soil organic matter, total nitrogen, total phosphorus, and alkaline dissolved nitrogen can not be directly related to the level of yield, if the thickness of the tillage layer is taken into account, organic matter, total nitrogen, and total phosphorus can be obtained. The content (percentage multiplied by the weight of the arable layer) coincides with the production rank. When the amount of fertilizer is too high, the yield increase of kiln fertilizer will be reduced. However, the range of reduction varies among soils, with less reduction in black soil and chernozem, and more reduction in salinized meadow soil. Therefore, it is generally believed that low-productivity soils and soils with low nutrient content have high yields for increased fertilization, thus increasing the amount of fertilizers. On the contrary, soils with high productivity and high nutrient content are considered to have low yield-increasing effects. Therefore, it is necessary to reduce the amount of fertilizers. It is wrong. There is a certain dependence relationship between the ratio of nitrogen and phosphorus content in soil and the optimal ratio of nitrogen to phosphorus for fertilization. The smaller the ratio of nitrogen to phosphorus in the soil itself, the higher the N/P ratio of fertilization should be. The ratio of alkaline to nitrogen-to-phosphorus phosphorus ratio 4 was used as the dividing line, which was exactly the same as the 2:1 and 1:1 ratios of the optimal nitrogen and phosphorus ratio for fertilization. Through two years of experiments, it was firstly determined that soil nutrient content, high-yield soil, and low-yield soil were determined by soil NPK analyzer. Both nitrogen and phosphorus fertilizers and organic fertilizers were necessary, and there was a significant increase in yield for corn. Therefore, there is no effect of high-yield soil fertilization within the scope of the test, so it should be less fertilization; low-yield soil fertilization effect, and therefore should be more regularity of fertilization. Especially for nitrogen fertilizers, the level of soil nitrogen has no direct effect on the level of nitrogen use efficiency. The ratio of nitrogen and phosphorus nutrient content in soil, especially the ratio of available nitrogen and phosphorus nutrient content, can be used as a reference to determine a reasonable combination of N and P fertilizers. When the ratio of alkaline nitrogen dissolved in the test soil to the content of the phosphorus in the Olsons is less than 4, the N/P ratio for fertilization in maize should be 2:1; when the ratio is greater than 4, the ratio should be 1:1. Outside Assembly Flat Press Production Line Outside Assembly Flat Press Production line is one new technology machine with high efficiency than inside assembly especially produce less than 2000mm insulating glass.Machine inclue Feeding section,washing and drying section,storage section,aluminum put section,outside assembly section,press section and output section. Double And Triple Glass Machinery,Advanced Insulating Glass Production Line,Ce &Iso-9001 Approved Insulating Glass Machine,Low-E Insulating Glass Production Line JINAN WEILI MACHINE CO LTD , https://www.weiliglassmachine.com