Because of High C:N ratio of many crop residues it's decomposition rate is slow. In What way the c: n ratio is impacting the the process of decomposition , mineralisation of nutrients and it's availablity to crops.
I don't think , we can really work out the most effective C: N ratio of different crop residues , most important is how to maintain a functionally active C:N ratio in soil to regulate soil fertility functions
Concept of carbon-nitrogen ration(C:N ratio) is related with the rate of decomposition of the crop or organic residues...High C:N ratio means more carbon with less nitrogen while under lesser C:N ratio, there will be more nitrogen as compared to carbon...the role of nitrogen is very essential for optimizing the decomposition processes or influencing the degradation of organic stuffs...under wider C:N ratio, though there will be more carbon but availability of nitrogen is less thereby very slower decomposition processes.so there should be narrower C:N ratio so as to initiate or fasten decomposition processes...under conservation agriculture practices, there will be spread of huge amount of plant residue therefore extra amount of nitrogen is to be required to initiate the decomposition as there will be wider C:N ratio as more carbon...
C:N ratio plays a major role in recycling of crop residues, if the C:N ratio is > 20:1 it favours immobilization, which makes N unavailable and if the ratio is < 20:1 it favours mineralization, which helps in recycling of crop residues and makes minerals available to the plants
Mineralization, simply is a process of conversion of organic form of any of the nutrient to inorganic forms while immobilization is the reverse process by which inorganic form converted into organic form...in general, inorganic form is the available form (either cation or anions) which is taken up by the plant with the process of absorption translocation and assimilation in question...this C:N ratio governs the whole process of mineralization as well as immobilization thus this ratio influence nutrient recycling processes to a greater extent...
C:N ratio plays a major role in recycling of crop residues, if the C:N ratio is > 20:1 it favours immobilization, which makes N unavailable and if the ratio is < 20:1 it favours mineralization, which helps in recycling of crop residues and makes minerals available to the plants .Crop residues like paddy have high C:N ratio >50:1,decomposition takes place at very slow rate. Because mineralization processes are carried out by bacteria which needs N in form of protein for their growth and development, with increasing population of these bacteria nitrogen content is further reduced because it gets immobilized in bacteria body.
Soil microbial activities are greatly influenced by C:N ratio of the organic material they are breaking down. The microbes require Nitrogen in addition to the carbon from organic materials to synthesize their own proteins and to continue breaking down the C-compounds. A high C:N ratio greater than 30 means the microbes have insufficient Nitrogen for their normal biochemical activities and therefore the entire decomposition process slows down. To speed up the process of decomposition such high carbon materials need an external source of additional Nitrogen.
At a high C:N ratio the soil microbes withdraw Nitrogen from the soils to bridge the deficit for its biochemical processes during the breakdown of the high carbon material. The result is that soils are robbed of its Nitrogen. This diminishes the Nitrogen available for plant uptake; the crops lose an important nutrient for some time. Too bad for the crop !
The best C:N ratio is 24 : 1 then microorganisms will use 16 units of C and keep 8 unit for maintenance.
The lesser is the C:N ratio of the residue, better it is for conservation agriculture. So preferably C:N ratio of residues less than 15:1 works effectively. That's why seed weed having one of the lowest C:N ratio works like wonder.
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