The application of organic fertilizer is a fine tradition of agricultural production. An extremely important principle in crop nutrition package fertilizer is to give equal importance to organic fertilizer and inorganic fertilizer, so as to greatly improve the fertilizer efficiency and economic benefits and achieve the five goals of “high yield, high quality, high efficiency, ecology and safety” in agriculture.
Organic fertilizer is the main source of organic matter in cultivated soil and the direct supplier of nutrients for crops. A large number of practices have shown that the unique role of organic fertilizer in supplying effective nutrients for crops and fertilizing and improving soil cannot be replaced by chemical fertilizers.
a. Organic fertilizer is a complete fertilizer
Organic fertilizer contains rich organic matter and nutrients required by various crops. It not only contains a large amount of nutrients, but also contains medium and trace nutrients with complete nutrients. First of all, nitrogen nutrition. Before the rise of chemical fertilizer industry, the supply of soil nitrogen almost entirely depended on organic fertilizer. Under the condition of high level of chemical fertilizer production, organic fertilizer still occupies a very important position in replenishing soil nitrogen.
Although the nitrogen effectiveness in organic fertilizers is lower than that in chemical fertilizers, the nitrogen loss rate is lower after being applied to the soil, which allows more nitrogen to remain in the soil. Therefore, applying organic fertilizers is more helpful in maintaining and increasing the nitrogen reserves in the soil than applying chemical fertilizers.
As for the phosphorus in organic fertilizers, it can directly supplement the available phosphorus in the soil, especially the phosphorus in pig and cattle manure can be 75% or more of superphosphate or potassium dihydrogen phosphate in the current season. The organic acid in organic fertilizers can promote the dissolution of insoluble phosphates in the soil, and has the ability to complex or chelate calcium, magnesium, iron, and aluminum ions in the soil to form stable compounds and reduce phosphorus fixation.
The potassium in organic fertilizers exists in an inorganic state, so it is highly effective. In addition, organic fertilizers can also supplement nutrients such as calcium, magnesium, and trace elements in the soil, and make most of them have high effectiveness.
b. Replenishment and renewal of soil organic matter
The amount of organic matter is an important indicator of soil fertility. Rich soil organic matter is a necessary condition for high, stable, and low-cost crop yields. Because the application of organic fertilizer is an important means of replenishing and renewing soil organic matter. According to statistics, soil organic matter converted from organic fertilizer accounts for two-thirds of the annual production of soil organic matter in cultivated soil in southern my country. According to research, the annual production of soil organic matter depends on the amount of organic matter entering the soil each year and the humification coefficient of various organic matter.
c. Improve soil physical and chemical properties
(1) Improve soil structural properties.
After organic fertilizer enters the soil, it can condense to form new humus through the action of microorganisms, and has a strong composite ability with soil particles, which can increase the organic-inorganic composite degree, significantly promote the formation of soil water-stable aggregates, and effectively improve and enhance soil structure. According to the research of the Soil and Fertilizer Research Institute of the Chinese Academy of Agricultural Sciences, the application of green manure, straw, or a mixture of half and half of both can increase the number of aggregates larger than 0.25 mm and their water stability. In the experiment, the best area for the application of half green manure and half straw was followed by the straw application area, and the green manure application area ranked third.
(2) Improve soil physical properties.
Because the aggregates bonded by organic matter are loose and porous, they have high water stability, absorb water without dispersing, and are fine soil particles. They can be contained in the structured aggregates and between aggregates at the same time. At the same time, the effect of organic matter on soil permeability is closely related to water holding capacity, which can enhance soil water retention rate and capillary water holding capacity, thereby reducing evaporation. Therefore, the application of organic fertilizers can easily coordinate the proportion of the “three phases (solid phase, liquid phase, gas phase)” of the soil, thereby promoting soil nutrient transformation, facilitating crop root extension and nutrient absorption, increasing soil water content, and enhancing crop drought resistance. For saline-alkali soil, it can also accelerate soil desalination, inhibit salt return, improve soil, and fertilize soil.
d. Improve the activity of soil microorganisms and enzymes
After organic fertilizers are decomposed, they can provide energy and nutrients for the life activities of soil microorganisms, thereby promoting microbial reproduction, enhancing microbial respiration, ammoniation, and nitrification, and can also enhance the activity of dehydrogenase, protease, urease, amylase, etc. in the soil.
e. Improve the utilization rate of chemical fertilizers
When the organic matter in organic fertilizers decomposes, a large amount of organic acids will be produced. These organic acids promote the dissolution of mineral nutrients in soil and fertilizers, which is beneficial to the absorption and utilization of crops and significantly improves the utilization rate of chemical fertilizers.
f. Stimulate growth, improve quality, and improve the quality of crops
Some acidic substances and physiologically active substances generated during the decomposition of organic fertilizers can promote the germination of crop seeds and root growth. In addition, organic fertilizers are comprehensive and rich in nutrients, especially containing medium and trace nutrients, sugars, fats and amino acids that are most suitable for crop absorption and utilization, which significantly improves the nutritional quality, taste quality, appearance quality of crop products and reduces the nitrate content of food.
According to research, compared with conventional application methods, the combined application of organic fertilizers and inorganic fertilizers can increase the protein content of wheat and corn by 2%-3.5%, amino acids by 2.5%-3.2%, and gluten by 1.4%-3.6%; the nicotine content in tobacco leaves can reach 2%-3%, the chlorine content is less than 1%, and the yield of upper and middle tobacco leaves can be increased by 4%-20%; the content of water-soluble sugar, theophylline, tea polyphenols and water-soluble phosphorus in tea leaves can be increased; the quality rate of garlic can be increased by 20%-30%, the content of allicin can be increased by 0.9%-1.1%, and the protein content can be increased by 0.84%; the nitrate content in vegetables can be reduced, and the vitamin C content can be increased; the crude fat in soybeans can be increased by 0.56%, and the linoleic acid and oleic acid can be increased by 0.31%-0.92% respectively.
An important content that affects agricultural production is to configure a certain amount of refined commercial organic fertilizers such as ecological organic fertilizers and biological organic fertilizers in the base fertilizer, implement the principle of giving equal importance to organic fertilizers and inorganic fertilizers, and achieve the purpose of replenishing soil organic matter, improving soil structure, and improving the utilization rate of chemical fertilizers.
