Utilization Status and Application Prospect of Organic Fertilizer

Fertilisers have long been an important agricultural production resource, greatly increasing the yield of farming. The annual use of chemical fertilisers in China amounts to 42.14 million tonnes, accounting for 35% of the world, and the average application level is 368 kg/hm2, which greatly exceeds the maximum limit of 225 kg/hm2 set by other developed countries to prevent chemical fertilisers from causing harm to soil and water bodies, ranking first in the world. Due to long-term blind, excessive and unreasonable fertilizer application will deteriorate soil properties, reduce soil fertility, cause water environment pollution and accumulation of heavy metals in the soil, bringing different degrees of pollution and damage to the environment and agricultural production. In order to improve the soil environment and protect the ecological environment, an important way to achieve sustainable agricultural development, the use and promotion of organic fertilizers is slowly becoming a new trend that deserves our attention and research. 

I. Classification of organic fertilizers and their functional role 

Organic fertilizers are mainly rich in organic matter, including amino acids, organic acids, peptides and other organic components, followed by a certain amount of nitrogen, phosphorus, potassium and other inorganic nutrients. Organic fertilisers are mostly made from plant residues or animal excreta, and are often referred to as farmyard fertilisers. 

(a) Organic fertilisers are classified according to raw materials 

At present, according to the different raw materials of organic fertilizer can be divided into 6 categories, manure and urine fertilizer, straw, green manure, biogas fertilizer, mineral fertilizer and some miscellaneous fertilizer. 

1, manure and urine fertilizer. Generally is a mixture of human or livestock manure and urine direct use. Human and animal, poultry excrement is the residue of food discharged after digestion, its main components are lignin fibres and hemicellulose, fats, proteins, organic acids and phosphorus, silicon, calcium, magnesium, potassium, sodium and other salts and chlorides, as well as a small amount of faecal odour, faecal bile and pigments. 

2. Straw. Straw is now a common worldwide attention to a fertilizer yield measures, in the elimination of straw burning caused by atmospheric pollution at the same time there is an increase in fertilizer and yield. Straw can increase soil organic matter, improve soil structure, loosen soil, increase porosity, reduce capacity and promote microbial activity and crop root development. Straw to the field to increase fertilizer yield effect is significant, generally can increase yield 5% ~ 10%, but if the method is not appropriate, will also lead to increased soil disease, crop disease aggravation and lack of seedlings (stiff seedlings) and other undesirable phenomena. So take reasonable measures to return straw to the field in order to play a good return effect. Straw can be returned to the field according to the way can be divided into direct return to the field and indirect return to the field two. 

(1) Direct return to the field. The direct return of straw to the field is relatively simple, convenient, fast and labour-saving. The number of fields returned to the field is high, and it is generally more common to use the direct field return method. Direct return to the field is divided into two kinds: turning and mulching. Turning is done after the crop has been harvested and the straw is turned into the soil before the next crop is sown or transplanted. Mulching is the direct application of crop straw or stubble to the soil surface. 

(2) Indirect return. Indirect field return mainly includes composting and over-belly return. Composting is the return of crop straw into compost, compost, etc. Crop straw is fermented and then applied to the soil. Its form has anaerobic fermentation and aerobic fermentation 2 kinds. Anaerobic fermentation is to put the straw after the pile, closed without ventilation; aerobic fermentation is to put the straw after the pile, in the bottom of the pile or pile with ventilation ditch. The fermented straw can accelerate the decomposition of humus to make a better quality organic fertiliser, which can be returned to the field as a base fertiliser. The straw is used to feed cattle, horses, pigs, sheep and other livestock after the straw is first used as feed and then digested and absorbed by the livestock into manure and urine, which is then applied to the soil and returned to the field. Straw over the belly to return to the field, not only can increase livestock products, but also can increase a large amount of organic fertilizer for agriculture, reduce agricultural costs, and promote a benign agricultural ecological ring. 

3, green fertilizer. Green manure is made of green plant system into fertilizer, is a nutrient complete biological fertilizer source, divided into wild green manure and cultivated green manure, such as purple yew, camas, hairy beans, etc.. Planting green manure is not only an effective way to increase the source of fertiliser, but also has a great effect on improving the soil. Green manure converts insoluble nutrients in the soil for crop absorption and utilisation. 

(1) Green manure provides rich nutrients for the soil. The young stems and leaves of various green manures are rich in nutrients and once decomposed in the soil, they can greatly increase the organic matter and nitrogen, phosphorus, potassium, calcium, magnesium and various trace elements in the soil. 

(2) Green manure converts insoluble nutrients in the soil for absorption and utilisation by crops. The organic acids produced by the secretions and decomposition of green manure crops during growth and after tilling can convert insoluble phosphorus and potassium in the soil into effective phosphorus and potassium that can be used by crops. 

(3) Green manure can improve the physical and chemical properties of the soil. After being turned into the soil, green manure decomposes continuously under the action of micro-organisms, in addition to releasing a large number of effective nutrients beneficial to crop growth. 

(4) Green manure can promote the activity of soil microorganisms. After green manure is applied to the soil, fresh organic energy material is increased, which makes microorganisms multiply rapidly and their activities are enhanced, promoting the formation of humus and the effective of nutrients and accelerating soil maturation.

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