Soil is form as a result of weathering of rocks. There are 5 factors that effect weathering of rock and soil formation. These factors are organisms,climate,time,topography and landscape settings and parent material,When we consider organic material it consist of living,dead plant and animal dynamic material. There are more advantages from organic materials to soil such as,increase infiltration,increasing of water holding capacity,increase work ability. Organic material on soil contain fibers,That fibers can absorb water and prevent from drying. This gives the best nutrient for microbes. Therefore,the soil rich in organic matter consist with huge amount of microbes. They support to decompose of organic and inorganic matter with the help of enzymes. Such as,oxidoreductases,hydrolases,lyasas and transferases. Oxidoreductases support to to transfer of electrons from 1 molecule to another. Hydro-lases supports to nutrient mineralization and protein breakdown. Lyases degrades cell walls and membranes of bacteria and fungi. And also it help to transfer functional group from 1 molecule to another. As a result,of these enzymes organic and inorganic matter decomposed and release essential nutrient for plants. As it the work-ability of soil increases. The structure of soil increase as a consequence of these factors.
There are 5 chemical properties of soil such as pH,cation exchange capability,essential plant nutrient,nutrient movement and root-soil interaction. Soil is as mixture of clay,air,water,sand and decomposing organic matter. Clay particles and decomposing materials release cations such as K+ Na+ Ca2+ that plays a very major role in soil. The water of soil solubilize the nutrient and produce bulk of nutrient solution(soil solution)and there is very wonderful relationship ,that is ,Root Soil interaction. As a result of these relation the nutrients absorb to plants. The microbes in soil produce nutrient exchange sites. Micro -organisms In soil produce symbiotic associate that can see. Rhizophere,mycorrhiza,rhizosphere are the root field or the physical location around the root. The rhizosphere is in two types that are endohrhyizosphere and ectorhizosphere place around the soil.
The rhizoplain that adhere to many micro organisms to root it it difficult to distinguish and also there is an area that is non-rhizosphere. That is a zone that is not penetrated by plant root. It has less microbial activity. There are 4 types of organic materials in rhizosphere that are exudates secretes,Lycates and plant mucilage. Exudates are low molecular weight compounds released from plant cells Lycates that release from plant in a non-metabolic manner. Secretions that is metabolically released from plant cells. Lycates that release from plant cells as a result of autolysis. Polysaccharide secrete by plants can see high micro organism concentration around the root. So as a result of these organic materials .Mucilage are insoluble organic compounds of 4 different origins. These are mucilage secretes by golgi organelles in root cap cells,hydrolysates of the polysaccharide of the primary cell walls. Mucilage secreted by epidermal cell, root hairs bacterial degradation of dead epidermal cells. The root exudates low molecular weight compounds act as a messenger .Micro organisms produce energy using that exudates through the metabolism. There are several functions of root exudates such as ;keep the soil around the soil moist,obtain nutrients,change chemical properties around the soil .Plant cell can produce anti-microbial agents,As a result of it the pathogenic harmless advantageous bacterial population reduces. So,root exudates attach microbes to the root. As a result of this adhesive nature,nutrients get soluble in exudates .So, it support to absorb nutrient to plants. There is larger benefit to plants of rhizosphere that are inhabit the activity of pathogens produce phytohormones, as a result of it crop yield increases. And also,rhizosphere support to nitrogen fixation. Rhizobium,Bradyrhizobium with legumes fix nitrogen and also rhizosphere support to solubilize inorganic materials a result,of it nutrient of soil is increases also rhizosphere produce sticky organic compounds. And also rhizosphere support to reduce pH of the soil. rhizosphere bacteria produce many types of acidic compound using their metabolism such as formic acid ,lactic acids.
There is another microbial plant symbiotic association that is known as Mycorrhiza Fungi. The mean od Mycorrhiza is fungus and root. In a mycorrhizal association ,the fungus colonize the host plant roots tissues either interact cellularly as in arbuscular mycorrhizal fungi or extracellular;ally as in ectomycorrhizal fungi. The association is sometimes mutualistic. mycorrhizal spread in large area ,especially Phosphorous absorb as PO-4 and amount of PO-4 donate symbiotic plant. As a result of it crops increase the yields. Fungi can penetrate solid materials using both physical and chemical tools,The mycelial growth form allows fungi to explore its weak spots on the rocks or gain surface. Due to enzymes,acids the inorganic material in rocks get soluble as a result of it,composition of rock gets changed and make better place for the growth of plants.And also,these fungi be the major reason to make soil aggregrates.Due this fungal hypha ,soil particles bind together fungal secretion is also a main reason for it.As a result , of these things the soil develop.
These every microbial activity depend on soil environment. When soil environment is unfavorable these activities breakdown. But the case is micros can survive in broad range. Now we will discuss about the soil temperature ,H2O,soil,O2 substrate in soil environment. Microbes widely spread on the surface of soil because of nutrients. Most of organic matter can easily find surfaces therefore no. of microbes can find from a surface is high. When we go to the deep of soil number of microbes decreases as as result of it unfavorable conditions occur. Not only that the oxygen concentration too decreases when we go to the deep of the soil as result of it aerobic microbes cannot survive ,also nutrient of soil decreases. The soil microbes are spread in a broad area. I will talk about this further more from my next article.
Rajarata University of Sri Lanka