To produce organic and healthy crops, compensating for lost nutrients and improving soil quality is one of the most widely used modifications, in addition to chemical fertilizers, organic and biological fertilizers. Compost, organic acids and vermicompost are the most important biofertilizers that will be briefly described.
compost :
Compost is derived from the Latin word Compositus and means to put together. Vermicompost is the result of a semi-aerobic process (about 80% humidity) carried out simultaneously by a specific species of worms, fungi, bacteria and actinomycetes. The type of compost can be prepared with different quality based on its raw material. Composts can be made from plant debris, animal waste, poultry waste or edible mushroom waste. High quality compost is typically made with low salinity from plant residues with a low carbon to nitrogen (C / N) ratio. On the other hand, in case of using edible mushroom bedding materials or poultry manure, especially laying hens, the resulting compost will have a high degree of salinity, which due to the drought stress in the country’s agricultural and garden lands, the consumption of this type of compost It is worrying. Unless the quality of this type of compost after processing has been approved by the Soil and Water Research Institute and has received a registration number
Table 6 shows the characteristics of two samples of compost obtained from the bed of edible fungi of the Faculty of Agriculture, Tarbiat Modares University, Karaj University (Spent compost) and a sample of compost processed from the waste of Neka wood cutting factory in Mazandaran.
Vermicompost :
Earthworms are arguably the most useful terrestrial animals that play a role in improving the physical properties of the soil and improving its aeration conditions and water equations. As a result of the activity of these animals, the process of composting organic waste is accelerated and a useful compound called vermicompost is obtained, which, like compost, is of significant nutritional and breeding importance. Vermicompost is a material obtained from the growth medium of the worm, which remains in the environment after being excreted from the digestive system. Therefore, this substance is a collection of worm excrement along with decomposed organic matter and also worm carcasses which has a great nutritional value for the plant. The product called vermicompost has more organic matter in terms of quality and is rich in organic acids such as humic acid and nutrients that are absorbable to the plant and has plant growth stimulants and various enzymes. This combination is granular in appearance and dark in color. Table 7 shows the results of chemical analysis of the average of two vermicompost samples and the allowable concentration of contaminants. The chemical properties of vermicomposts vary greatly depending on their raw material. The result is careful selection of raw materials so that the consumer does not face the problem of salinity and many pollutants such as cadmium, lead, arsenic, etc.,
Organic acids:
The secretion of low molecular weight organic acids by some plant cultivars is one of the important strategies in increasing the availability of phosphorus and zinc in the soil. Organic acids such as citric acid and oxalic acid are released from plants in relatively large amounts of phosphorus and zinc in the absence of nutrients, and in increasing the solubility of nutrients, including phosphorus in the rhizosphere. Participate. According to studies in this field, organic acids are able to remove available phosphorus in calcareous soils by lowering soil pH, dissolving calcium carbonate, competing with phosphorus in adsorption on mineral surfaces, calcium deposition and phosphorus release from calcium phosphate as well as indirectly. Increase by increasing the growth of microorganisms and intensifying mineralization (Nezami, 2015)
