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Similar to SSAC 353 lecture no. 5 & 6 introduction and imp. of organic matter, composition, types of organic matter
SSAC 353 lecture no. 5 & 6 introduction and imp. of organic matter, composition, types of organic matter
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- 2. Importance of OrganicManures Soil makes living system Food for soil flora & fauna Store house for nutrients Improves chemical properties Improves physical properties of soil Improves buffering capacity of soil Releases nutrients from soil minerals
- 7. Basic Definitions Decomposition Biochemicalbreakdown of organic wastes (crop residues, plant originated waste, sewage/sludge) or conversion of complex organic compounds into simpler compounds often accomplished by microbial metabolism Compost Organic residues which have been mixed, piled and moistened, with or without addition of fertilizer or lime and generally allowed to undergo mesophilic (30-40oC) and thermophilic (50- 60oC)decomposition until the original organic material are substantially altered or decomposed. Organic recycling Returning of plant nutrients removed by the crops from soil through addition of organic material of crops after harvesting is referred as organic recycling C:N ratio It’s a ration of the mass of carbon to the mass of nitrogen in a substrate. (Relative quantity) C:N ration 10:1 means there is a ten units of carbon for each unit of nitrogen in the substrate and it indicate suitability of particular organic material for making compost along with its period.
- 9. Carbohydrate 60-70% Ash 5% Chemicalcomposition of undecomposed organic matter
- 12. Organic Matter Easily degradable Simplesugars, amino acids & amides CO2,H2O NH3 etc Moderately degradable Cellulose, hemicellulose, protein complex carbohydrates Simple compounds like sugars amino acids quinoids etc Difficultly degradable Tannins, lignin's, keratins, chitin Complex substances like quinines, polyphenols etc
- 13. Organic matter/organic material/naturalorganic matter Refers to the large source of carbon based compounds found within natural and engineered, terrestrial and aquatic environments. It is matter composed of organic compounds that have come from the remains of organisms such as plants and animals and their waste products in the environment. Organic molecules can also be made by chemical reactions that don't involve life. Basic structures are created from cellulose, tanins, chitin, and lignin, along with other various proteins, lipids, and carbohydrates. Organic matter is very important in the movement of nutrients in the environment and plays a role in water retention on the surface of the planet.
- 14. Sources of organic matter Primarysources Plant origin like wheat straw, sugarcane trash, groundnut cake, castor cake etc. Secondary sources Animal origin like cow dung, urine, night soil, bone meal Organic Recycling Returning of plant nutrients removed by the crops from soil through addition of organic material of crops after harvesting of crops is referred as ….
- 15. Organic sources basedon their occurrence Rural residues Farm waste, dry leaves of plants Urban waste Night soil, sewage, sludge, city waste etc Industrial waste Sugar, dairy, paper, alcohol industrial waste etc.
- 16. CO2, H2O, More energy,more biomass CO2 + CH4+Alcohol + NH3 + H2 + Less energy Less biomass Extracellular enzymes Complex polymers Cellulose/lignin/proteins (High molecular weight substances) Monomeric units like sugars, amino acids, phenols or Low molecular weight substances Decomposition process
- 18. C:N ratio It isdefined as the ratio of the weight of organic carbon to the weight of total nitrogen in the soil or organic matter. It is the relationship between organic matter and nitrogen content of soils or plants. Carbon is present in the form of organic matter or humus. Carbon content varies from 1% in coarse textured soils to 3.5 % in grassland soils Poorly drained soils (Aquepts) may contain 10% or more carbon Ideal C:N ration is between 10:1 to 12:1
- 19. Organic matter &Nutrient interaction in soil favors….. •Plant and animal residue upon degradation provides N/P/S and micronutrients •Microbial biomass serves as nutrient storage •Conversion of organic N/P/S to soil available nutrients through microbes Organic N/P/S NH4/PO4 3- /SO4 2- Mineralization Immobilization
- 20. Crop Residues C:NRatio Legumes and young green leaves 10:1 to 30: 1 Sugarcane trash 100 : 1 Saw dust 600:1 Bacteria/Fungi/Actinomycets 5:1 to 10:1 Cultivated soils 8:1 to 15:1
- 21. Importance of C:Nratio…..Pertaining to soil • When organic residues with wider C:N ratio - added to soil, competition between plant & microbes for N Example: Residues > 300:1 C:N ratio • Heterotrophic microbes become active and increase their population with production of more CO2 through their respiration • Under these conditions, the NO3-N level in soil decreases as microbes utilize the native soil N • N-is immobilized at the initial stages and is not available to plant • Addition of plant residues with high C:N, C:P or C:S ratio favors initial net immobilization followed by mineralization
- 22. Importance of C:Nratio…..Pertaining to soil • Wider C:N ratio (more than 40) in substrates such as oat straw or any other promote immobilization of available N in the soil/compost, resulting in a slowing of the decomposition due to limited N availability. • Addition of external N/P enhances the rate of decomposition in soil/ during composting. • Metabolic processes during composting further affect the pH of the material. • Compost microorganisms operate best under neutral to acidic conditions, with pH's in the range of 5.5 to 8. During the initial stages of decomposition, organic acids are formed. ... As composting proceeds, the organic acids become neutralized, and mature compost generally has a pH between 6 and 8.
- 24. Organisms Temperature range Psychrophilesof 0–15 °C Psychrotrophs 4°C and 25 °C Mesophiles 20 °C to about 45 °C Thermophiles above 50 °C. Temperature Range for Microbes
- 26. Importance of C:Nratio…..Pertaining to soil •C:N ratio indicate suitability of particular organic residue for making compost and also helps to decide period of decomposition •Microbes require N for synthesis of amino acids and proteins (immobilization) thus in wider C:N ratio organic material N is limiting factor for the growth of microbes hence require more time for decomposition.
- 30. C:N Ratios asRelated to Organic Matter Decomposition If C:N ratio 30:1 Immobilization < 20:1 Mineralization 20-30:1 immobilization = mineralization
- 31. Effect of C:Nratio on CO2 evolution Crop residues with LOWER C:N ratio…… ……. at EARLY stage more microbial activity and more CO2 evolution and decomposition rate becomes faster •Crop residues with HIGHER C:N ratio……………. at LATER stage CO2 evolution RATE increases decomposition rate becomes slower •Wider C:N ratio of crop residues will release more loss of carbon as CO2 and CH3
- 32. Effect of C:Nratio on soil availability of nutrients If we add crop residues with wider C:N ratio in the soil – the microbes in soil feed on that material having carbon but they also need N/P for biosynthesis of proteins.
- 33. 1) C:N ratiomainly controls decomposition rate in soil C:N ratio mainly controls rate of decomposition in soil. 1 WIDE C: N ratio NARROW C: N ratio 2 Slow decomposition rate Fast decomposition rate 3 Immobilization of nutrients Mineralization of nutrients 4 Carbon and energy wastage in large quantities Carbon and energy starvation occur 5 Microbial activity restricted due to N limitation Competition among the microorganism for available N Ex : Speed of decomposition becomes slow with more/wide C/N ratio residue or low N percentages Low/narrow C/N ratio or high N percentages speeds the decomposition rate. Importance of C: N ratio
- 34. 2) It isa source of food and energy for plants I Soil microbes require carbon for building essential organic compounds Ii They also need sufficient N to synthesize N containing cellular components, such as amino acids, enzymes and DNA iii Microbes have 8:1 ratio means – microbes must incorporate into their cells about 8 parts of carbon for every 1 part of N.
- 35. 3) It controlsN availability in soils/plants I If C/N ratio of OM is about 25:1, the soil microbes will have to scavenge the soil solution to obtain enough N Ii Thus, the incorporation of high C/N residues will deplete the soil native N, causing higher plants to suffer from N deficiency. iii While low C/N ratio (<20) Organic matter helps in increase in N content of soil for plants and organisms.
- 36. 4) The decayof organic matter can be delayed; if sufficient nitrogen to support microbial growth is neither present in the material nor available in the soil 5) Influence of C/N ratio on Soil ecology; The soil ecosystem consists of saprophytic bacteria and fungi and nematodes, protozoa and earthworms that grow rapidly on organic residues as food source. 6) It is related to release of available N, total organic content and accumulation of humus.
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