Sources of Plant Nutrients in the Soil

Sources of Plant Nutrients in the Soil:

Plants obtain mineral nutrients through root uptake from the soil solution. Sources of these soluble nutrients in soil include:

Decomposition of plant residues, animal remains, and soil microorganisms
Weathering of soil minerals.
Fertilizer applications.
Manures, composts, biosolids (sewage sludge), and other organic amendments such as food processing byproducts
N-fixation by legumes.
Atmospheric deposition, such as N and S from acid rain or N-fixation by lightning discharges.
Deposition of nutrient-rich sediment from erosion and flooding.

Losses of Plant Nutrients from the Soil:

Mineral nutrients also can be lost from the soil system and become unavailable for plant uptake. Nutrient losses are not just costly and wasteful, they can be a source of environmental contamination when they reach lakes, rivers, and groundwater.
Nutrient losses occur through:

Runoff – loss of dissolved nutrients in water moving across the soil surface.
Erosion – loss of nutrients in or attached to soil particles that are removed from fields by wind or water movement.
Leaching – loss of dissolved nutrients in water that moves down through the soil to groundwater or out of the field through drain lines.
Gaseous losses to the atmosphere – primarily losses of different N forms through volatilization and denitrification.
Crop removal – plant uptake and removal of nutrients from the field in harvested products

The accumulation of crop nutrients in the topsoil by recycling and fallow ash, the increase of soil organic matter and the suppression of the weeds, pest & diseases.

Composting:

Organic residues, when composted, undergo decomposition by the digestive of bacteria, fungi and other soil micro fauna. Within two or three months, a dark, pulverised material rich in humus is produced.Most of the organic N, S and P are converted into plant available inorganic forms.The C/N ration decrease and pH increases.Well decomposed compost is a good source of available nutrients which are supplied to the plants slowly and gradually.Certain organic constituents present in the compost act as chelating agents and help in the absorption of certain trace elements.

Benefits of Using Compost

Benefits of Using Compost:

• Improves the soil structure, porosity, and density, thus creating a better plant root environment.
• Increases moisture infiltration and permeability of heavy soils, thus reducing erosion and runoff.
• Improves water-holding capacity, thus reducing water loss and leaching in sandy soils.
• Supplies a variety of macro and micronutrients.
• May control or suppress certain soil-borne plant pathogens.
• Supplies significant quantities of organic matter.
• Improves cation exchange capacity (CEC) of soils and growing media, thus improving their ability to hold nutrients for plant use.
• Supplies beneficial micro-organisms to soils and growing media.
• Improves and stabilizes soil pH.

Reduce Chemical Inputs,Increase Yield !!!!!

Reduce chemical inputs.Increase yields:

Soil nutrients are important for plant growth and development.Plants obtain carbon,hydrogen and oxygen from air and water.But other essential nutrients like nitrogen,phosphorus,potassium,calcium,magnesium,sulfur and more must be obtained from the soil.

Fertilizers contaminate the soil with impurities, which come from the raw materials used for their manufacture. Mixed fertilizers often contain ammonium nitrate (NH4NO3), phosphorus as P2O5, and potassium as K2O. For instance, As, Pb and Cd present in traces in rock phosphate mineral get transferred to super phosphate fertilizer.Since the metals are not degradable, their accumulation in the soil above their toxic levels due to excessive use of phosphate fertilizers, becomes an imperishable poison for crops.

The over use of NPK fertilizers reduce quantity of vegetables and crops grown on soil over the years. It also reduces the protein content of wheat, maize, grams, etc., grown on that soil. The carbohydrate quality of such crops also gets degraded. Excess potassium content in soil decreases Vitamin C and carotene content in vegetable & fruits.