Unit4 - Subjective Questions

The differences between organic manures and chemical fertilizers are as follows:

Definition:
Integrated Nutrient Management (INM) refers to the maintenance of soil fertility and plant nutrient supply at an optimum level for sustaining the desired productivity through optimization of the benefits from all possible sources of organic, inorganic, and biological components in an integrated manner.

Primary Goals:

• Maintain Soil Health: To enhance the physical, chemical, and biological properties of the soil.
• Sustainability: To sustain agricultural productivity without harming the environment.
• Efficiency: To improve the use efficiency of chemical fertilizers.
• Cost Reduction: To reduce the cost of cultivation by utilizing locally available organic resources.
• Balance: To minimize nutrient imbalances and antagonisms.

Preparation (Trench Method):

1. Site Selection: A high-lying area away from water sources.
2. Trench Dimensions: Typically length, width, and depth.
3. Filling: A mixture of dung, urine-soaked litter, and straw is placed in the trench daily. When a section rises above ground level, it is plastered with mud and dung slurry.
4. Decomposition: The material is left to decompose for 3–5 months.

Nutrient Profile (Average):

• Nitrogen ():
• Phosphorus ():
• Potassium ():
• It also contains essential micronutrients and organic matter.

Organic manures are classified based on their volume per unit of nutrient content:

1. Bulky Organic Manures:

• Description: These manures contain small percentages of nutrients and are applied in large quantities (tonnes/ha). They primarily supply organic matter.
• Characteristics: High volume, low nutrient density, improves physical soil properties.
• Examples: Farm Yard Manure (FYM), Compost, Green Manure, Vermicompost.

2. Concentrated Organic Manures:

• Description: These are made from raw materials of animal or plant origin and contain higher percentages of major plant nutrients compared to bulky manures.
• Characteristics: Low moisture content, slower decomposition than chemical fertilizers but faster than bulky manures.
• Examples: Oil-cakes (Groundnut cake, Mustard cake), Blood meal, Fish meal, Bone meal.

Process of Vermicomposting:

1. Preparation: A bedding of chopped straw/leaves is prepared.
2. Inoculation: Earthworms (e.g., Eisenia foetida, Eudrilus eugeniae) are released into the organic waste mixture.
3. Digestion: Worms consume the organic waste, grinding it in their gizzard and digesting it with enzymes.
4. Excretion: The waste passes through the worm's gut and is excreted as 'castings' (vermicasts).
5. Harvesting: The castings are harvested after 45–60 days.

Advantages over Conventional Compost:

• Higher Nutrient Content: Vermicompost generally has higher N, P, and K than ordinary FYM.
• Growth Regulators: Contains plant growth hormones like auxins and cytokinins.
• Enzymes: Rich in beneficial enzymes (amylase, lipase, cellulase).
• Microbial Load: Higher population of N-fixers and P-solubilizers.
• Speed: Faster process than traditional composting.

Green Manuring: The practice of growing undecomposed green plant tissue and incorporating it into the soil to improve physical structure and soil fertility.

Distinction:

1. Green Manuring In-situ:

   • Concept: Green manure crops are grown in the field itself and plowed into the soil at the flowering stage.
   • Examples: Sunhemp (Crotalaria juncea), Dhaincha (Sesbania aculeata).
   • Best for: Areas with sufficient moisture or irrigation.

2. Green Leaf Manuring:

   • Concept: Green leaves and tender twigs are collected from shrubs and trees grown on bunds or wastelands and brought to the field for incorporation.
   • Examples: Glyricidia (Gliricidia sepium), Pongamia (Pongamia pinnata).
   • Best for: Areas where growing a dedicated green manure crop is not feasible.

INM involves the judicious combination of the following components:

1. Chemical Fertilizers:

   • Used to meet the immediate, high nutrient demands of high-yielding varieties.
   • Must be used efficiently (split application, placement) to reduce losses.

2. Organic Manures (FYM, Compost, Vermicompost):

   • Improve soil physical health (structure, aeration).
   • Provide micronutrients and buffer the soil pH.

3. Biofertilizers:

   • Microbial inoculants like Rhizobium, Azotobacter (N-fixers) and PSB (P-solubilizers).
   • Eco-friendly and cost-effective supplements.

4. Green Manures:

   • Leguminous crops incorporated into the soil to add organic matter and fix atmospheric Nitrogen.

5. Crop Residues:

   • Incorporation of stubble/straw helps recycle nutrients (K, Si) and increases Soil Organic Carbon (SOC).

6. Legumes in Rotation:

   • Including pulses helps restore soil fertility through biological nitrogen fixation.

The Carbon-Nitrogen () Ratio determines the rate of decomposition and nutrient cycling.

• Decomposition Speed:

  • Low (): Rapid decomposition. Microbes have enough Nitrogen to break down Carbon structures efficiently.
  • High (): Slow decomposition. Microbes are Nitrogen-starved.

• Nitrogen Cycle (Immobilization vs. Mineralization):

  • If materials with a wide ratio (e.g., sawdust, straw, ) are added, microbes consume available soil Nitrogen to build their bodies, causing Nitrogen Immobilization (temporary unavailability for plants).
  • If materials with a narrow ratio (e.g., legume residues, ) are added, excess Nitrogen is released into the soil, causing Net Mineralization (availability for plants).

• Ideal Range: A ratio of approximately to in stable soil organic matter is ideal for fertility.

Oil-Cakes as Manure:
Oil-cakes are the solid residue remaining after oil is extracted from seeds. They are concentrated organic manures rich in Nitrogen () and also contain Phosphorus and Potassium. They are quick-acting compared to bulky manures; their Nitrogen becomes available usually within a week or two of application.

Classification:

1. Edible Oil-Cakes:
   • Suitable for cattle feed; used as manure only when unfit for feeding.
   • Examples: Groundnut cake (), Mustard cake, Sesame cake.
2. Non-Edible Oil-Cakes:
   • Not suitable for feeding cattle due to toxic content; used exclusively as manure.
   • Examples: Castor cake (), Neem cake (), Mahua cake.
   • Note: Neem cake also possesses nitrification inhibition properties.

Necessity for Sustainable Agriculture:

1. Restoration of Soil Fertility: Continuous use of chemical fertilizers leads to micronutrient deficiencies and secondary nutrient depletion (S, Mg). INM replenishes these.
2. Physical Soil Health: Organic components improve structure, preventing compaction and erosion.
3. Environmental Protection: Reduces nitrate leaching into groundwater and eutrophication caused by fertilizer runoff.
4. Productivity Stagnation: Addresses the 'yield plateau' observed in intensive farming where higher fertilizer doses no longer increase yields.

Constraints in Adoption:

• Availability: Inadequate availability of organic manures (FYM) in sufficient quantities.
• Labor Intensive: Collection, preparation, and application of bulky manures require significant labor.
• Bulky Nature: High transport and handling costs due to low nutrient density.
• Slow Results: Organic components take time to mineralize, unlike the immediate visible effect of urea.
• Knowledge Gap: Lack of technical knowledge regarding biofertilizers and optimal combinations.

Poultry Manure:

• Properties: It is one of the richest sources of plant nutrients among bulky organic manures. The droppings ferment very quickly. Fresh poultry manure contains approx , , and .
• Uses: ideal for vegetable crops and short-duration crops due to rapid mineralization. Care must be taken to avoid 'burning' roots with fresh manure.

Sheep/Goat Manure:

• Properties: The dung contains approx , , and .
• Uses (Sheep Penning): A common practice is Sheep Penning, where herds are kept in the field overnight. Their urine and dung fall directly onto the soil, reducing handling losses and transport costs. Urine is very rich in Nitrogen and Potassium.

An ideal green manure crop should possess the following characteristics:

1. Fast Growth: It should accumulate sufficient biomass in a short period (45–60 days).
2. Leguminous Nature: Capable of fixing atmospheric Nitrogen () through root nodules.
3. Deep Root System: To mine nutrients from deeper soil layers and open up the subsoil.
4. Succulent Foliage: Soft tissues that decompose rapidly when incorporated into the soil.
5. Hardiness: Ability to grow on poor soils and resist pests/diseases.
6. Low Water Requirement: Should not compete heavily with the subsequent crop for soil moisture (or should be drought tolerant).

Enriched Compost:
Ordinary compost is often low in Phosphorus. Enrichment involves adding mineral fertilizers or amendments during the composting process to increase the nutrient content of the final product.

Phosphocompost:

• Definition: Compost specifically enriched with Phosphorus.
• Preparation: Low-grade Rock Phosphate (which is not directly soluble) is added to the composting pit along with organic waste.
• Mechanism: During decomposition, organic acids (e.g., citric acid, malic acid) are produced by microbes. These acids solubilize the insoluble Rock Phosphate, making the Phosphorus available ( availability increases).
• Additives: often Pyrites or Phosphate Solubilizing Bacteria (PSB) are added to accelerate the process.

Night Soil:

• Definition: Human excreta (solid and liquid).
• Nutrients: Richer in N, P, and K than FYM (approx , , ).
• Treatment: Direct application is unhygienic. It is treated via the Poudrette system (mixing with soil/ash and drying) or modern sewage treatment.

Sewage Sludge:

• Definition: The solid portion settled during sewage water treatment.
• Issues: While nutrient-rich, it may contain Heavy Metals (Lead, Cadmium, Mercury) and pathogens.
• Use: Must be treated (activated sludge process) and tested for toxicity before application to non-edible crops (like cotton/timber) to prevent heavy metals from entering the food chain.

Calculation:

1. Quantity of FYM: .
2. Nitrogen Content: .
3. Total Nitrogen ():
   
   
   

Result: The farmer adds 75 kg of Nitrogen per hectare.

Difference from Urea:

• Availability: Urea hydrolyzes rapidly, making N available within days. FYM N is organic; it must undergo mineralization. Only about of the 75 kg (approx 22.5 kg) is available to the crop in the first year.
• Residual Effect: The remaining N from FYM becomes available in subsequent years, whereas Urea has little residual effect and is prone to leaching.

The efficiency and speed of composting depend on:

1. C:N Ratio: The starting material should have a C:N ratio between and . Too high slows it down; too low causes Ammonia loss.
2. Moisture Content: Optimum is . Too dry stops microbial activity; too wet creates anaerobic conditions (bad smell).
3. Aeration (Oxygen): Essential for aerobic bacteria (Thermophiles). Achieved by turning the pile or using perforated pipes.
4. Temperature: The process goes through a mesophilic phase () and a thermophilic phase (). High temp kills pathogens and weed seeds.
5. pH: Ideally neutral (). Extreme acidity slows decomposition.
6. Particle Size: Shredding materials increases surface area for microbial attack, speeding up decomposition.

Role in INM:
Biofertilizers are preparations containing living cells of efficient strains of microorganisms that help crop plants uptake nutrients.

1. Nitrogen Fixation:

   • Symbiotic: Rhizobium (for legumes) fixes atmospheric in root nodules.
   • Free-living: Azotobacter and Azospirillum (for cereals like wheat/rice) fix N in the rhizosphere.
   • Blue Green Algae (BGA) & Azolla: specifically used in paddy fields.

2. Phosphorus Solubilization:

   • PSB (Phosphate Solubilizing Bacteria): Genera like Pseudomonas and Bacillus secrete organic acids to solubilize fixed soil Phosphorus.

3. Nutrient Mobilization:

   • VAM (Vesicular Arbuscular Mycorrhiza): Fungi that extend root reach, helping in P and water uptake.

Benefit: They can substitute of chemical fertilizer requirements.

Common Losses:

1. Leaching: Water soluble nutrients (N and K) are washed away by rain if stored in the open.
2. Volatilization: Nitrogen is lost as Ammonia () gas if the heap dries out or heats up excessively.
3. Non-collection of Urine: Since of N and most K is in urine, failing to collect it (via bedding) results in massive loss.

Minimization Techniques:

• Covered Pits: Storing manure in pits protected from rain and sun.
• Compaction: Compacting the heap to reduce aerobic oxidation (though some air is needed initially).
• Use of Gypsum: Adding Superphosphate or Gypsum () helps fix Ammonia, reducing volatilization.
• Proper Bedding: Using straw/litter to absorb urine effectively.

Edible Oil Cakes:

• Source: Residue from seeds like Groundnut, Sesame, Mustard, Soybean.
• Primary Use: Feeding cattle (Livestock feed) due to high protein content.
• Agricultural Use: Used as manure only when spoilt or if the market price is low. They generally decompose faster.

Non-Edible Oil Cakes:

• Source: Residue from seeds like Castor, Neem, Mahua, Karanj.
• Primary Use: Exclusively used as Manure because they contain toxic or bitter compounds (e.g., Azadirachtin in Neem) making them unfit for feed.
• Added Benefit: Many non-edible cakes (especially Neem) have insecticidal properties and act as Nitrification Inhibitors, slowing down urea hydrolysis and increasing Nitrogen Use Efficiency.