Write down the importance of organic matter.

The importance of soil organic matter is relation to soil fertility and physical condition is widely recognized. However, organic matter contributes to the fertility or productivity of the soil through its positive effects on the chemical, physical and biological properties of the soil.

The role of organic matter in soil is so varied and extensive that it makes one think of the claims printed on old time patent machine labels; fortunately these for organic matter are all true.

1. Organic matter influence the soil color due to presence of adequate amount of organic matter in soil, the color will be brown to dark brown or black.

2. Organic matter binds soil particles (sand, silt and clay) into structural units called aggregates. Hence organic matter has a profound effect on the improvement of soil structure and thereby soil maintains favorable condition of aeration and permeability.

3. The rate of infiltration and percolation of water is enhanced by the application of organic matter in the soil.

4. Water holding capacity is increased by the application of organic matter. The amount of available water in sandy and loamy soils increase with the application of organic matter.

5. Organic matter reduces plasticity, cohesion, stickiness etc. in soils containing appreciable amounts of clay.

6. Organic matter increases the ability of the soil to resist erosion.

7. Organic matter affects the bulk density of soil which in turn influences the soil porosity favorably.

8. Organic matter reduces losses of surface soil by wind erosion by forming granules with soil particles.

9. During decomposition or organic matter various organic acids and CO2 liberate in the soil which help to reduce alkalinity of soil.

10. Organic matter also acts as a buffering agent. Due to such buffering effect it reduces the likelihood of damage to plant roots from excessive acids, alkalis or added to it in the form of fertilizers and thus stabilizes the soil pH.

11. Organic matter has solubilizing effect on some mineral compounds present in the soil.

12. Organic matter can be considered as a store house of various nutrients essential to plant growth. Organic matter is the source of 90-95% of the nitrogen in unfertilized soil. In addition, organic matter supplies available phosphorus, sulfur and some other micronutrients like Fe, Mn, Cu, and Zn to the soil and thereby increases the nutrient as well as improves the soil health.

13. Organic matter temporarily absorbs heavy metal pollutants which are usually derived from applied waste waters used for irrigation. Adsorption of pollutants helps clean contaminated water.

14. Organic matter serves as a source of energy for both macro and micro organisms and helps in performing various beneficial functions in soil.

15. Organic matter acts as a chelate. Chelate is any organic compound that can bound to a metal more than one bond and from a ring or cyclic structure by that bonding.

16. Various organic substances like vitamins, antibiotics and growth promoting compounds namely auxin are produced by different micro-organism during decomposition of various organic matter.

17. Organic matter interact with organic pesticides and it can absorb N and S oxides from the atmosphere with have implications with respect to both the yield of crop plants and the quality of the environmental respectively.

Harmful effects of organic matter:Many beneficial effects or organic matter in the soil are

counter balanced by harmful influence under certain conditions. A few harmful effects are given below:

1. Organic matter is an energy anti carbon source fro many diseases organism ensuring their longer periods of survival in soils.

2. Excessive amounts of organic matter create a problem for mixing the soil thoroughly and abstract easy planting.

3. Various organic residues produce different phytotoxins during their decomposition which make them undesirable as organic matter. Alleopathy is also active. Alleopathy is any direct or indirect harmful effect of one plant on another through the production and release of toxic substance into the environment.

Describe the sample and products of organic matter decomposition:As a result of enzymic action of organic matter and

consequent formation of humus simple end products are formed immediately. The simple end products are either used by plants or microorganisms or readily lost, if not utilized and sink to minimum unless fresh tissues are frequently added.

As the enzymatic changes of soil organic matter proceed, simple end products begin to manifest themselves. Some of them especially carbon dioxide and water appear immediately. Others are nitrate nitrogen etc. accumulate only after the peak of two vigorous decomposition stage is over, and the general purpose decay organisms decrease in number.

The common simple products which are formed due to the activity of soil micro organisms are:

I. Carbon base components: CO2, CO3²ˉ,HCO3ˉCH4, C (elemental carbon).

II. Nitrogen base compounds: NH4+, NO2+, NO3ˉ, N(gaseous)III. Sulfur base compounds: S, H2S, SO3²ˉ, SO4²ˉ, CO2

IV. Phosphorus base compounds: H2PO4, HPO4²ˉ, PO4³ˉ(in acidic soil)

V. Other sample products: H2O, H+, OHˉ, O2, H2, Na+, K+, Ca²+, Mg²+, Fe²+, Zn, Mn, Ge etc.

Distinguish between peat and muck:Peat Muck

1. An organic soil that contains more than 50% organic matter & the

organic matter is partially decayed or non-decayed, is called peat.

1. An organic soil that contain 20-50% organic matter & the organic

matter is completely decomposed, is called muck.

2. The kind of plant in the peat can be identified.

2. The plant materials of muck cannot be identified.

3. Peat soils are coarse/fine textured depending on the nature of deposited

plant residues.4. Light in color

3. Muck soils are quite fine textured as the original plant materials are

broken down.4. Light in color

Describe the influence of organic matter on soil properties.

Or*Describe in detail the importance of soil organic matter in soil fertility.

Or Write down the function of soil organic matter on soil properties.

Organic matter is an essential part of a productive soil. Although it remains in the soil in a small amount it is a store house of plant nutrients in the soil. It influence on the physical, chemical and biological properties of the soil, the functions of organic matter are described as below

Effect of physical properties of soil1. Effect of organic matter on soil erosion :

Coarse organic matter on the soil surface reduces impact of the falling raindrop and permits clear water to seep gently into the soil. As a result surface run off of water and erosion are reduced. And there is more available water for plant growth. Coarse organic matter on the soil surface reduced losses of soil by wind erosion.

2. Effect of organic matter on soil temperature :Organic matter makes a soil black colored. Black colored soil absorbs more heat than lighter colored soil. This temperature is necessary for seed germination. On the other hand surface mulches lower soil temperatures in the summer and keep the soil warmer in winter.

3. Effect of organic matter on soil evaporation :Evaporation losses of water are reduced by organic matter.

4. Effect of organic matter on soil structure :Decomposing organic matter produces slimes and microbial gums which help to form and to stabilize desirable soil structure.

5. Effect of organic matter on decay of plant root :When the plant roots decay they provide channels, through which new plant roots grow. These channels are effective in transmitting water and plants use this water from the channels.

6. Effect of organic matter on water holding capacity :Organic matter increases water holding capacity in the soil. It holds water fairly tightly, thus the permanent wilting percentage is increased.

Effect on chemical properties in soil:

1. Effect of organic matter on nutrient availability:Upon decomposition organic matters supply some of all nutrients needed by growing plants. When external condition are favorable for rapid plant growth. The same conditions favor a rapid release of nutrients from the organic matter. Most of the soil nitrogen occurs in organic combination which releases nitrogen in the soil for plant.

2. Effect of organic matter on ion exchange:Humus as well as organic matter is store house for the exchangeable and available cations such as K+, Ca²+. Mg²+, etc. temporary it holds NH4+ ion in an exchangeable and available form. It increases ion exchange capacity of the soil.

3. Effect of organic matter on availability of phosphorus:Fresh organic matter has a special function in making available soil phosphorus in acid soil. Upon decomposition organic matter releases citrates, oxalates, tetrahedral and lactates, which combine with iron and aluminum more readily than does phosphorus. As a result the availability of phosphorus ion increased.

4. Effect of organic matter on solubility of soil minerals:Upon decomposition of organic matter, reduced various kinds of acids and carbon dioxide which reacts with soil minerals and dissolve it and releases plant nutrient elements.

5. Effect of organic matter on buffering:Organic matter as well as humus contains various kinds of exchangeable cations which resist the soil pH after making a small amount of acid and alkali.

6. Effect of organic matter on reclamations of alkalinity:After decomposition of organic matter and inorganic acids are released. These acids help to reduce alkalinity of soil.

* Effect of biological properties of soil:

1. Effect of organic matter on the source of food and energy of microorganisms.

Soil organic matter is the main food and energy source of soil microorganisms. Through decomposition of organic matter microorganisms take up their food elements. So organic matter serves as a source of energy for the growth of soil micro-organisms.