How to Use Organic Fertilizer Reasonably in Vegetable Production
Applying organic fertilizer in vegetable production can achieve the goal of continuously supplying various nutrient needs in the crop root zone, gradually improve the organic matter and buffering capacity of vegetable garden soil, and play an important role in reducing soil-borne diseases and continuous cropping obstacles. Therefore, vegetable production has always attached importance to the application of organic fertilizer. However...
Applying organic fertilizer in vegetable production can achieve the goal of continuously supplying various nutrient needs in the crop root zone, gradually improve the organic matter and buffering capacity of vegetable garden soil, and play an important role in reducing soil-borne diseases and continuous cropping obstacles. Therefore, vegetable production has always attached importance to the application of organic fertilizer. However, in the development of the modern intensive, high-yield, high-efficiency and high-quality vegetable industry, in addition to continuing to maintain the input of organic fertilizer, there is also a large amount of chemical fertilizer input and the interactive input of large amounts of water and fertilizer. For the sustainable development of vegetable production, it is necessary to make a new evaluation of the problems and scientific strategies of organic fertilizer application under the new situation.
Among the problems currently existing in organic fertilizer application in vegetable fields, the first is that the application amount is large and nutrient input is excessive, especially excessive nitrogen and phosphorus input, which has caused environmental problems in some areas. For example, because organic fertilizers such as manure and urine and food processing residues have the characteristic of relatively high salt content, excessive application of organic fertilizer may lead to soil salt accumulation.
The second is that the types of organic fertilizer are single, mostly livestock and poultry manure and urine such as chicken manure and pig manure. Taking chicken manure as an example, it contains more nitrogen and phosphorus nutrients, but its carbon-to-nitrogen ratio is very low, so its function in regulating soil structure is insufficient.
The third is the safety of application. For example, organic fertilizers made from garbage often contain pollutants such as heavy metals and radioactive substances; organic fertilizers made from animal manure and urine also contain certain amounts of heavy metals such as zinc, copper and arsenic due to residues of feed additives; in addition, organic fertilizers made from straw often contain certain pathogenic microorganisms, such as harmful bacteria and insect eggs. Market surveys have also found that some vendors add alkali to manure and urine fertilizer in order to increase the volume of organic fertilizer, and such organic fertilizers with excessive alkalinity affect vegetable growth, etc. Once these problematic organic fertilizers are applied to vegetable fields, they may cause harmful components in vegetable products to exceed standards, posing a threat to food and environmental safety.
Reasonable application countermeasures for organic fertilizer in vegetable fields. First, the fertilization strategy in vegetable production should follow the principle of combining organic and inorganic fertilizers. The application amount of organic fertilizer should be reasonable, and more is not always better. First, understand the nutrient content of the organic fertilizer applied, fully estimate the amount of nitrogen, phosphorus and potassium nutrients it supplies to crops, deduct the amount of nutrients that the organic fertilizer can provide, and then use chemical fertilizers to supplement the insufficient part. However, in current production practice, vegetable farmers often do not count organic fertilizer nutrients but only chemical fertilizer nutrients, resulting in the widespread problem of excessive fertilization.
Regarding the appropriate ratio of organic to inorganic fertilizers: taking the supply of nitrogen needed by vegetable crops throughout the year as an example, some countries suggest that the proportion of nitrogen from organic fertilizer should be 50%-60%. The Food and Agriculture Organization of the United Nations once recommended a ratio of organic nitrogen to inorganic nitrogen of 1:(0.4-1), and determining the application amounts of organic fertilizer and chemical fertilizer on this basis.
Second, select different types of organic fertilizer according to the quality characteristics of vegetable garden soil. New vegetable fields should use fermented organic fertilizers with high chemical nutrients and quick effects, such as manure and urine, green manure and cake fertilizer; old vegetable fields should use slow-release organic fertilizers rich in straw and subjected to composting and fermentation. Some old vegetable fields with severe continuous cropping obstacles achieve very good results by using straw bio-reactor technology, which uses straw to improve soil physical properties and also supplements sufficient carbon sources. Among the types of organic fertilizer, choosing compost products including manure and urine, straw and solid garbage can improve vegetable crop resistance and root-promoting effects, improve soil pH and soil structure, increase the amount of soil organic matter, passivate the activity of heavy metals in vegetable fields, and reduce the risk of heavy metal pollution.
Third, regarding the timing of organic fertilizer application, the general principle is that because organic fertilizer has slow-release characteristics, it should be applied as base fertilizer or bottom fertilizer before sowing or transplanting. It should not be used as topdressing; chemical fertilizer should be used for topdressing.
For this reason, a reasonable ratio of base fertilizer to topdressing should be formulated. For high-yield fruit vegetable crops, appropriately reduce the amount of base fertilizer and increase the amount of topdressing.
Finally, control the input of fertilizer and water in order to reduce the accumulation, leaching and runoff loss of nitrogen and phosphorus nutrients in vegetable fields and reduce non-point source pollution.
In short, in current vegetable production, it is necessary to vigorously publicize knowledge about the scientific application of organic fertilizer and popularize the concept of quantitative fertilization; promote composting and fermentation technology for organic materials, and help vegetable farmers use organic fertilizer safely and effectively, so as to achieve high yield, high quality and safety in vegetable production.