How to treat soil acidification with bio organic fertilizers?

The traditional way to control soil acidification in southern China is to use lime to adjust acidity and supplement calcium. Apply lime, adjust acidity and supplement calcium. Adjusting acidity and alkalinity can increase the effectiveness of nutrients, so acid adjustment (lime application) is equivalent to fertilization. After the autumn harvest, clean up the straw and weeds in the field, sprinkle 100kg of quicklime per mu, plow, rake evenly, and smoke fire manure, achieving multiple goals in one fell swoop. Using straw in the field and weeds in the corners of the field to smoke fire manure is also an effective measure to control soil acidification. Fire manure is alkaline and contains a high amount of potassium, which has the function of regulating soil acidity and supplementing potassium. The Tujia ancestors maintained soil acid-base balance and potassium element balance by applying fire manure. Apply Organic Fertilizer to balance acidity and alkalinity. Organic fertilizer has great buffering capacity and can regulate soil acidity and alkalinity. Long term application can balance acidity and alkalinity and enhance soil fertility. Cover cultivation to reduce leaching. Covering cultivation in agricultural production (plastic film covering and grass covering) can reduce the erosion of soil by precipitation and decrease the leaching of alkaline salt bases in the soil. Soil testing formula, precise fertilization, soil testing formula fertilization according to crop needs, reducing the amount of chemical fertilizer applied, can effectively prevent and control soil acidification. When applying nitrogen and phosphorus fertilizers, choose urea and diammonium phosphate, and reduce the amount of ammonium chloride, ammonium sulfate, and superphosphate used.

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Research and development of acid regulating bio organic fertilizers
The research and development of acid regulating bio organic fertilizers mainly focuses on four aspects: organic matter regulation, microbial regulation, acid regulating agents, and alkaline fertilizer regulation.
1. Choose organic matter with strong acidity. Amino acid molecules contain both basic amino and acidic carboxyl groups, which have the property of buffering acidity and alkalinity. When encountering alkaline substances, they bind with acid groups and lose their alkalinity; Encountering acidic substances, binding with amino groups, losing acidity. So we choose organic fertilizer raw materials with high amino acid content to produce acid regulating bio organic fertilizers. Organic matter with relatively high protein and total nitrogen content, as well as relatively high amino acid content, such as fermented cake, chicken manure, fish meat residue, etc. Humic acid also has a certain buffering effect on acidity and alkalinity, and has exchange, adsorption, complexation, chelation and other effects with metal ions. In addition, humic acid can promote the formation of colloids and aggregates in soil, reduce the exchange of Ca ions, Mg ions, K ions, Zn ions and other basic ions adsorbed on the surface of soil colloids by H ions, and resist and delay soil acidification. Therefore, organic fertilizer raw materials with high humic acid content are selected to produce acid regulating bio organic fertilizers. Generally, organic matter with high fat and total phosphorus content also has relatively high humic acid content. For example, fermented cake and lees.
2. Select microorganisms with acid regulating function. Photosynthetic bacteria belong to independent nutritional microorganisms. The bacterial cells themselves contain more than 60% protein and are rich in various vitamins, as well as coenzyme Q10, antiviral substances, and growth promoting factors. They use the light and heat received by the soil as energy to separate sulfur and hydrogen from hydrocarbons in the soil, turning harmful substances into harmless substances. They use plant root exudates, soil organic matter, harmful gases (such as hydrogen sulfide), carbon dioxide, nitrogen, and other substrates to synthesize sugars, amino acids, vitamins, nitrogen compounds, antiviral substances, and physiologically active substances. They are the main force for fertile soil and promoting plant growth. The metabolites of photosynthetic bacteria can be directly absorbed by plants and can also serve as nutrients for the reproduction of other microorganisms. Specific types of microbial agents need to be tested and screened, and excellent varieties should be selected to produce acid regulating bio organic fertilizers.
3. Choose to add acid adjusting agents. Amino acids and humic acids (especially potassium and sodium humate) are good acid regulating substances. In addition, there are also some acid regulating agents, such as polyglutamic acid and chitin, which are good acid regulating agents. Adding some acid regulating agents to bio organic fertilizers to produce acid regulating bio organic fertilizers.
4. Choose to add alkaline fertilizers or substances. The most alkaline fertilizers are calcium magnesium phosphate fertilizer, calcium magnesium phosphate potassium fertilizer, and diammonium phosphate also has a certain alkalinity. The most commonly used alkaline substance is lime, but caution should be exercised when adding lime as its alkalinity is too strong and can easily affect the effectiveness of nitrogen and phosphorus fertilizers. Ash from plants and trees is ideal due to its low alkalinity, low cost, and the presence of certain nutrients. Biological organic fertilizer products produced by adding alkaline fertilizers or alkaline substances should not have a pH too high, as it can easily reduce the effectiveness of the fertilizer.

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Use of acid regulating bio organic fertilizers
The humus in soil organic matter has a huge specific surface area and surface energy, strong adsorption performance, and high cation exchange capacity. It can buffer changes in H ion concentration in soil solutions, and combine with Al ions in soil to form complexes, reducing the saturation of Al ions in soil, alleviating soil acidity, and reducing the toxic effects of Al ions. The application of organic fertilizers and the harvesting of agricultural products are two mutually inverse processes. Increasing the application of organic fertilizers can effectively supplement the loss of base ions caused by the removal of agricultural products. On the one hand, it can provide nutrients and energy materials for soil organisms, increase the abundance and activity of microorganisms in the soil; On the other hand, the various organic complexes produced by microbial activity decomposing organic matter can enrich soil nutrients, improve soil nutrient availability, increase soil buffering capacity against acidity and alkalinity, improve soil structure, and increase soil cluster structure.
The mechanism of its action is that organic fertilizers are usually alkaline. With the application of organic fertilizers, a large number of salt based ions enter the soil, increasing the ion strength and cation exchange capacity of the soil solution. In addition, organic matter produces a large amount of acidic substances rich in functional groups such as hydroxyl and phenol during mineralization, which undergo coordination exchange with hydroxylated aluminum and iron oxides in the soil, consuming H ions in the soil. The organic acids produced by the decomposition of organic matter release carbon dioxide during further dehydroxylation and can also consume H ions in the soil.
1. Acidic organic fertilizer. Crop straw, livestock manure, green manure, and plant ash, which contain a large amount of nutrients, can improve soil fertility, increase the variety and activity of soil microorganisms, change their population distribution density, and reduce the content of exchangeable Al ions in soil. They are commonly used for acid soil improvement. Straw such as rice, soybeans, and peas can increase the content of exchangeable base ions in soil, while reducing soil acidity and exchangeable Al ion content. Livestock manure can increase soil pH to a certain extent and also reduce soil Cd activity. Green manure can effectively reduce the content of exchangeable H and Al ions in soil, increase CEC, enhance enzyme activity, and also increase the content of soil nutrient factors. Research has found that compared with the control area, the pH of soil planted with Gram columnar flowers for five and three years in acidic soil increased by 0.34 and 0.22, respectively. At the same time, the content of important nutrients in the soil increased significantly, and the longer the planting period, the more obvious the improvement in soil fertility. Grass ash itself is an alkaline fertilizer that can neutralize the acid in the soil, reduce soil acidity and the content of active aluminum, and promote the release of phosphorus elements, providing good environmental conditions for crop growth and microbial activity.

2. Microbial fertilizers. Microbial fertilizer is a specific microbial agent that contains a large number of active microorganisms. Its life activities can promote the transformation of substances in the soil, increase the absorption of nutrients by plants, improve crop nutrition, regulate crop growth, and prevent crop diseases and pests, thereby achieving the goal of increasing yield. In the experiment of soil improvement with composite microbial fertilizer in arid areas, it was found that the addition of composite microbial agents and organic compost can increase soil moisture content, reduce soil bulk density, increase soil porosity, improve soil acidity and alkalinity, maintain reasonable soluble salt content, and significantly increase the content of available nutrients in soil and the types and quantities of beneficial microorganisms such as bacteria, fungi, and actinomycetes in soil.
3. Biochar. Biochar belongs to black charcoal, which can not only neutralize soil acidity and reduce the toxic effects of aluminum on crops, but also increase the content of effective nutrients in soil and improve crop yield due to its rich nutritional elements. Indoor cultivation experiments showed that after treatment with different concentrations of two biomass materials, fruit charcoal and rice husk charcoal, soil pH significantly increased and the content of exchangeable acids decreased significantly compared to the control. Yuan Jinhua et al. used cultivation experiments to analyze the improvement effect of biochar prepared by adding rice husks on acidic red soil and yellow soil, and found that the addition of biochar resulted in two different types of soil. The cation exchange capacity and base saturation increased to varying degrees compared to the control treatment, improving soil nutrient utilization efficiency. The relevant research results indicate that the application of biochar in the first year has no significant effect on maize yield, but in the following three years, maize yield is significantly higher than that of soil without biochar application. Moreover, with the increase of biochar dosage, its yield increasing effect becomes more obvious.