Integrated Nutrient Management of Soil

The various components of integrated nutrient management are: 1. Organic Manures 2. Green Manures 3. Green Leaf Manures 4. Biofertilizers 5. Fertilizers.

Component # 1. Organic Manures:

Organic manures are the by-products of farming and allied industries derived from plant and animal sources. Application of 30 to 50 per cent of total nutrients in the form of organics would improve the physical properties of soil, provide congenial conditions for microbial activity, enhance the response of added nutrients, facilitate slow release of nutrients, reduce nutrient losses and provide a long term build-up of soil fertility.

Organic manures are of paramount importance not only in augmenting the crop production but also for making the agriculture more sustainable as an ecofriendly means of soil health management. Unlike inorganic fertilizers that supply only the major nutrients, organic manures serve as a store house of several plant nutrients and act as a good soil conditioner. They are broadly classified as bulky organic manures and concentrated organic manures.

(a) Bulky Organic Manures:

i. Farm yard manure.

ii. Compost.

iii. Night soil.

iv. Sewage and sludge.

v. Crop residues.

(b) Concentrated Organic Manures:

i. Oil cakes.

ii. Blood meal.

iii. Meat meal.

iv. Fish meal.

v. Bone meal.

Organic matter content in Indian soils is low and its improvement is essential to improve physical, chemical and biological properties of soil. This can be accomplished through addition of bulky and concentrated organic manures.

Component # 2. Green Manures:

Green manuring is the practice of growing lush plants and plough in situ when succulent to improve the soil properties. Green manures when it is incorporated into the soil, not only supply the nutrients, it improves the crop yield by enhancing soil fertility, improving soil structure, preventing soil erosion, and also improves the microbial activity.

Green manure crops suitable for different ecosystem are given below:

i. Daincha

ii. Manila agathi

iii. Sithagathi

iv. Sunhemp

v. Kozhingi

vi. Pillipesara, and

vii. Kalopagonium.

Component # 3. Green Leaf Manures:

Green leaf manuring is the practice of collecting green leaves and tender green twigs from shrubs and trees grown on bunds and waste lands and applying to the main fields for improving the fertility status of soil.

i. Neem

ii. Pungam

iii. Glyricidia

iv. Erukku, and

v. Subabul.

Component # 4. Biofertilizers:

Biofertilizers are defined as preparations containing live or latent cells of efficient strains of nitrogen fixing, phosphate solubilizing or cellulolytic micro-organisms. They accelerate microbial processes in the soil which augment the extent of availability of nutrients in a form easily assimilated by plants. Usage of biofertilizers as a part of integrated nutrient management helps in reducing the cost of production and supplements the chemical fertilizers.

The different groups of biofertilizers are as follows:

i. Rhizobium:

Suitable rhizobial strain is treated with pulses as seed inoculation which helps to increase the grain yield by fixing nitrogen from the atmosphere.

ii. Azolla:

Under rice ecosystem, it fixes atmospheric nitrogen (20-30 kg N/ha) through symbiotic association with blue green algae (Anabaena azollae). Incorporation of Azolla helps to increase the grain yield by 5 to 11 per cent.

iii. Azospirillum:

It is treated with sorghum, cumbu, ragi, maize and cotton as seed inoculation which fixes appreciable quantities of atmospheric nitrogen through associative symbiosis.

iv. Azotobacter:

It is capable of fixing atmospheric nitrogen as free living microorganisms. This should be treated with crops like rice, sorghum, ragi and maize thus saving 25 per cent of nitrogenous fertilizer.

v. Blue Green Algae:

It is suitable for rice and fixes atmospheric nitrogen in the form, which is easily assimilated. This alga has been estimated to contribute 25 to 30 kg of nitrogen per hectare per season.

vi. Phosphobacteria:

Free living bacteria in the soil (Bacillus megatherium, Bacillus circullans) helps in the mobilization of insoluble forms of phosphate into soluble forms, which are assimilated by the crop plants.

vii. Mycorrhizae:

It is a symbiotic association of fungi with the roots of seed plants. The mobility of nutrients mainly phosphorus and also zinc and sulphur from the soil to the plants is mediated by this association. This association also produces growth promoting substances, which stimulate plant growth thus increasing the yield.

(a) Ectotrophic Mycorrhizae:

The hyphae of fungi occur on the root surface and penetrate only the intercellular spaces.

(b) Endotrophic Mycorrhizae:

The hyphae of fungi occur mainly within cells of the host plants.

Component # 5. Fertilizers:

Fertilizers are essential inputs for boosting the output of crops as they provide adequate nutrients to crops. Their use in optimal quantities is essential for maintaining the fertility of soil to obtain the benefit of high yields.

The following practices can be adopted for increasing the fertilizer use efficiency:

i. Incorporation of basal dose of fertilizers.

ii. The inorganic fertilizers should be applied at optimum soil moisture content.

iii. Split application of fertilizers at important phenological stages of crop growth.

iv. Use of coated and slow release fertilizers.

v. Foliar spray of micronutrients to overcome the nutrient deficiencies.

vi. Application of enriched FYM to avoid fixation of phosphorus.

Factors affecting the efficient use of fertilizers and manures:

1. Soil Factors:

i. Soil texture

ii. Total nutrient content of soil

iii. Availability of nutrients

iv. Soil reaction

v. Soil erosion

vi. Drainage

vii. Soil management practices, and

viii. Presence of impermeable layer in the soil.

2. Climatic and Environmental Factors:

i. Temperature

ii. Relative humidity

iii. Rainfall

iv. Evaporation

v. Length of growing season/period

vi. Intensity of sunlight, and

vii. Duration of sunlight.

3. Crop Factor:

i. Cropping system

ii. Nutrient requirement of crops

iii. Crop adaptability to soil factors

iv. Crop production techniques, and

v. Crop residues.

4. Systems of Farming:

i. Wetland farming

ii. Gardenland or irrigated upland farming, and

iii. Dryland or upland farming.

5. Fertilizer Characters:

i. Nature of fertilizers

ii. Solubility of fertilizers

iii. Dosage of fertilizers, and

iv. Method of application of fertilizers.

The adoption of intensive agriculture involving more usage of inputs viz., fertilizers, herbicides, pesticides etc., after the introduction of high yielding varieties programme in 1966 resulted in increased production of food grains. Nevertheless, continuous use of large amounts of fertilizers in the recent years only had deleterious effect leading to decline in productivity owing to the non-availability of micronutrients.

The micronutrients can be supplied through various organic manures for averting the deficiencies thus favouring proper growth and development of crops. The projected availability of plant nutrients from varied organic sources in 2025 is equal to 7.25 mt. These organic sources of nutrients in combination with fertilizers will improve the fertility status of soil favouring high yields. This integrated approach may bring down the escalating cost of inorganic fertilizers substantially.