How to use organic fertilizer scientifically and safely

Fertilizers can be divided into chemical synthetic fertilizers (fertilizers) and organic (class) fertilizers, which in turn contain a variety of different types of fertilizers. The so-called organic (class) fertilizer refers to a kind of fertilizer containing organic matter, the current commercial organic fertilizer mainly includes commercial organic fertilizer, commodity organic inorganic compound fertilizer, commodity biological organic fertilizer, commodity organic inorganic biological compound fertilizer (commodity organic organic fertilizer) and commodity organic liquid fertilizer. Traditional organic fertilizer refers to farm manure, green manure, crop straw, etc., they do not have commercial, generally do not enter the market circulation, and commodity organic (class) fertilizer is the use of traditional organic fertilizer as raw materials processed into a variety of organic ingredients of a class of fertilizer, they have commercial, with agricultural industry standards or national standards.

More than 20 years ago, people usually talk about organic fertilizer is farm fertilizer, such as human livestock and poultry manure, straw fertilizer, green fertilizer, artificial compost or compost, etc., they are non-commercial organic fertilizers. However, with the rapid development of social economy, there is no labor force in the countryside to apply traditional farm fertilizers, and the effect of farm fertilizers to fertilize the soil is far overwhelmed by the effect of fertilizers in the season to increase production, the application of farm fertilizers has become a very rare thing.

However, constant (and often excessive) application of fertilizers, especially chemical nitrogen fertilizer, can lead to soil acidification, soil structure damage, soil microflora damage and low biological activity, reduced quality of agricultural products and loss of flavor. Therefore, on the one hand, China continues to vigorously promote the use of traditional farm fertilizers, such as planting and cultivation, straw directly returned to the field; On the other hand, it began to vigorously support the development of commodity organic (class) fertilizer industry, and centralized treatment of agricultural organic waste into decomposed compost, or further processing into a variety of commercial organic (class) fertilizer products.

The development of organic fertilizer industry is of great significance

Applying organic fertilizer is one of the main ways to improve soil fertility. Soil is the main natural resource of agricultural production, and crop production can be fundamentally said to be soil production. Because of its high microbial activity, high fertility soil has a stronger ability to eliminate environmental pollution, so that sudden pollution events will not immediately or more extent pollute agricultural products, and even enter the food chain and endanger human health. Due to its strong ability to coordinate soil water, fertilizer, air and heat, sustained and stable nutrient supply, and strong soil microbial and enzyme activity, high fertility soil can significantly improve the quality and flavor of agricultural products, and significantly extend the fresh life of vegetables and fruits, which is the theoretical basis for organic fertilizer cultivation and the production of "delicious food".

Only by applying organic fertilizers can the recycling of natural nutrients be realized. At present, China's annual agricultural organic waste resources are converted into about 60 million tons of nitrogen, phosphorus and potassium nutrients, of which less than half are used in farmland, and a considerable proportion of agricultural solid organic waste nutrient resources are lost in the environment, while China's annual fertilizer for crop production is converted into about 54 million tons of nitrogen, phosphorus and potassium nutrients, if the above organic nutrient resources are fully utilized. It can probably save about half of China's fertilizer nutrient input, which is a huge nutrient resource.

The application of organic fertilizer is conducive to environmental protection. Eutrophication of China's water environment mainly comes from the discharge of solid organic waste to water, and the emission of fertilizer nutrients from farmland only accounts for a small proportion. At present, the eutrophication degree of Chinese lakes is still very serious. For lakes such as Taihu Lake, Dianchi Lake, Chaohu Lake, Dongting Lake and Poyang Lake, the only way to prevent and control eutrophication is to cut off the input of organic and inorganic nutrients into the water. The development of organic (type) fertilizer industry and the protection of the water environment in the development of fertilizer industry is a great cause that integrates the fertilizer industry, soil fertilizer cultivation and water environment protection, and high-quality and high-yield crops.

The development of bio-organic fertilizer is one of the key ways to ensure the development of efficient agriculture. Biological organic fertilizer refers to a class of special organic fertilizers containing specific functions of microbial strains, and the production process has a secondary solid fermentation stage, it overcomes the shortcomings of the traditional concept of biological fertilizers (in fact, biological bacteria), that is, the content of bacteria is high but there is no organic carrier or very little organic matter, only as a inoculant, it is because there is no organic carrier. After these biofertilizes (biofertilizes) are applied to the soil, functional bacteria cannot colonize effectively in the soil, let alone play a role. After the application of bio-organic fertilizer in the soil, sufficient amount of organic matter can provide sufficient energy materials for the exogenous functional microorganisms, so that these exogenous functional microorganisms are easy to colonize and multiply in the soil. After the crop roots grow and secrete a large amount of root secretions, these exogenous functional bacteria that have been colonized in the soil can chemoattractant to the root surface and rhizosphere, realizing the control of the rhizosphere microflora. The beneficial rhizosphere bacteria can activate nutrients, stimulate plant root growth and antagonize soil-borne pathogens.

Scientific application of organic fertilizer should solve the problems of heavy metals, antibiotics and antibiotic resistance genes

Organic fertilizer (here refers to decomposed compost) in addition to the shortcomings of insufficient available nutrients, crop yield is not obvious in the season, there are some other shortcomings. For example, the use of livestock manure made of decomposed compost of harmful substances in the most concerned, in order to make better use of organic fertilizer, we should pay attention to source control, harmless treatment, scientific and rational use of organic fertilizer.

Based on the perspective of environmental protection, resource utilization and market acceptance, the current important organic fertilizer sources are livestock and poultry manure, crop straw and agricultural product processing waste from intensive farms, which are combined with high temperature aerobic composting and transformed into ordinary organic fertilizer with commercial properties and other functional organic (type) fertilizer products. The harmful substances in commercial organic (class) fertilizer products mainly come from livestock and poultry manure, and their types and contents vary greatly. However, the harmful substances that people are concerned about in general include two categories, one is heavy metals (including metalloid, hereinafter referred to as heavy metals); The other is antibiotics and Antibiotic resistance genes (ARGs).

Due to the ability to promote animal growth, improve feed efficiency and control and treat diseases, trace heavy metals (such as zinc, copper, arsenic, etc.) and veterinary antibiotics such as quinolones, beta-lactam, macrolides, sulfonamides and tetracycline antibiotics have been added to feed for a long time, and are widely used in intensive livestock and poultry farming around the world. However, the heavy metal elements and antibiotics added in feed can not be fully absorbed and metabolized in the animal body, most of them are excreted in the "original form" with feces and urine, and the content of trace elements such as copper, zinc, arsenic and antibiotics in livestock and poultry feces is directly related to the content of these elements and substances in feed. Animal gut microbes naturally contain a high abundance and diversity of ARGs, and the use of antibiotics may promote the abundance or diversity of ARGs in animal gut.

In order to achieve the safe application of commercial organic fertilizers made from livestock manure as raw materials, in addition to controlling the safe addition amount of heavy metals and antibiotics in aquaculture feed from the source, another effective way is to treat livestock manure before agricultural use to remove or safely transform heavy metals, antibiotics and ARGs in livestock manure to the maximum extent. High temperature aerobic composting treatment is an effective way of harmless and resource recycling of livestock and poultry manure, its purpose is to make the unstable organic matter in compost raw materials gradually degrade and transform into stable compost products through high temperature aerobic fermentation, which is harmless to crops and can improve soil.

In the composting process, heavy metals cannot be degraded by microorganisms, and degradable organic matter decomposes and synthesizes stable humus and volatile substances under the action of microorganisms, resulting in a decline in the total mass of composting materials and a relative concentration of heavy metals. It is generally believed that the total amount of heavy metals in compost can not accurately reflect the potential environmental impact of heavy metals, and the ecological and environmental effects of heavy metals are closely related to their biological availability, and the chemical form of heavy metals is more worthy of attention than the total amount. The composting process exhibits passivation effect on a variety of heavy metal elements, which is because the composting process is a complex dynamic aerobic fermentation process that is jointly completed by organic materials under the action of physical chemistry and microorganisms. After rapid decomposition and transformation of organic matter, complex and stable humus substances are gradually formed, which can chelate with heavy metal elements. Effective combination and passivation of these elements, such as the content and distribution rate of exchange copper and zinc after composting treatment are reduced, indicating that aerobic composting has a certain passivation effect on heavy metals and reduces the biological availability of heavy metals.

The application of organic fertilizer should consider the heavy metal content, the amount of organic fertilizer application and the maximum annual bearing capacity of the soil, because heavy metals are cumulative, long-term application will accumulate in the soil, and there is a risk of exceeding the capacity of the soil. Although the soil itself is a rich reservoir of antibiotics and ARGs, we also need to pay attention to the environmental risks of antibiotics and ARGs introduced into the soil through organic fertilizer application. Reducing heavy metals, antibiotics and ARGs from the source into the aquaculture industry is an important measure to prevent the environmental risks brought by the application of organic fertilizer. At present, China has relevant regulations such as the safe use of feed additives. Regulations on the amount and type of veterinary antibiotics used (" Veterinary Pharmacopoeia of the People's Republic of China (2015 edition) "and" Veterinary Drug Quality Standards (2017 edition) "), etc., to ensure the safety of organic fertilizer raw materials. In addition, the research on quality control standards of organic fertilizers, optimization and standardization of composting process parameters is also very important to guide the safe production and application of organic fertilizers.