4. (c) What is the need for integrated nutrient management (INM)? Suggest INM for transplanted rice.

Need for Integrated Nutrient Management (INM)

The reliance on chemical fertilizers alone has led to various problems, highlighting the critical need for INM in modern agriculture. The primary reasons necessitating INM are:

• Declining Soil Fertility and Health: Continuous use of synthetic fertilizers without adequate organic matter replenishment depletes soil organic carbon, degrades soil structure, reduces microbial activity, and leads to nutrient imbalances. INM helps in improving and sustaining the physical, chemical, and biological functioning of the soil.
• Increasing Fertilizer Costs: The rising cost of chemical fertilizers burdens farmers, especially small and marginal landholders. INM, by incorporating organic and biological sources, reduces the dependency on expensive synthetic inputs, thereby lowering cultivation costs.
• Environmental Concerns: Excessive use of chemical fertilizers leads to nutrient leaching into groundwater, runoff into surface water bodies, and greenhouse gas emissions (e.g., nitrous oxide from nitrogen fertilizers). INM minimizes these losses, reducing environmental pollution and promoting carbon sequestration. Studies indicate INM practices can significantly reduce methane emissions compared to conventional nutrient management.
• Low Nutrient Use Efficiency (NUE): Conventional fertilizer application often results in low nutrient use efficiency, meaning a significant portion of applied nutrients is lost and not utilized by crops. INM synchronizes nutrient supply with crop demand, enhancing the availability of both applied and native soil nutrients, leading to better NUE.
• Sustainable Crop Productivity: INM provides balanced nutrition to crops, preventing hidden deficiencies and antagonistic effects caused by nutrient imbalances. This holistic approach ensures sustained optimal crop growth and higher productivity over the long term, adapting to site-specific characteristics.
• Addressing Micronutrient Deficiencies: Modern intensive agriculture often leads to widespread micronutrient deficiencies in soils. Organic manures and biofertilizers in INM help mobilize and make these micronutrients available to plants, addressing deficiencies that chemical fertilizers alone might not fully resolve.

Integrated Nutrient Management (INM) for Transplanted Rice

Transplanted rice, a major staple crop, requires a robust nutrient management strategy to ensure high yields while maintaining soil health. An effective INM for transplanted rice involves a balanced application of organic, inorganic, and biological nutrient sources, along with appropriate cultural practices:

1. Soil Testing and Analysis:

The foundation of INM is understanding the existing soil nutrient status. Regular soil testing (e.g., through the Soil Health Card Scheme) helps determine deficiencies and excesses of macro and micronutrients, pH, and organic carbon content. This guides the precise application of fertilizers.

2. Organic Manures:

Organic sources are vital for improving soil structure, water retention, microbial activity, and slow-release nutrient supply.

• Farmyard Manure (FYM) or Compost: Apply 5-10 tonnes per hectare (t/ha) of well-decomposed FYM or compost 15-20 days before transplanting and thoroughly mix it with the soil during puddling. This enhances overall soil health and provides essential nutrients.
• Green Manuring: Incorporating green manure crops like Dhaincha (Sesbania aculeata), Sunhemp (Crotalaria juncea), or Mung bean 4-6 weeks before transplanting can add 60-90 kg N/ha and improve soil organic matter.
• Rice Straw/Crop Residue Management: Instead of burning, incorporate rice straw into the soil. Rice straw is a source of N, P, K, Si, Ca, Mg, and other nutrients. This helps in nutrient recycling and improves soil organic carbon.

3. Inorganic Fertilizers:

Chemical fertilizers provide readily available nutrients, which are crucial for the initial growth of transplanted rice. The dosage should be based on soil test recommendations and targeted yield.

• Nitrogen (N): Apply nitrogen in split doses to minimize losses. A common recommendation is 75% of the Recommended Dose of Fertilizer (RDF) through chemical fertilizers in combination with organic sources.
  • Basal application: 40% of the N dose at transplanting, especially if soil fertility is low. Avoid large basal applications (>40 kg N/ha).
  • Tillering stage: 40% of the N dose at maximum tillering stage.
  • Panicle initiation stage: 20% of the N dose at panicle initiation stage.
  • Foliar application of NPK (19:19:19) can supplement soil application, especially during critical growth stages (e.g., 25, 50, and 75 days after transplanting) to enhance nutrient uptake.
• Phosphorus (P): Apply the full recommended dose of Phosphorus (e.g., as Single Super Phosphate - SSP) at the time of final land preparation or transplanting, as P is relatively immobile in the soil.
• Potassium (K): Apply Potassium (e.g., as Muriate of Potash - MOP) in split doses: half as basal and the remaining half at the maximum tillering or panicle initiation stage. This prevents K deficiency, which can stunt plant growth and reduce tiller number.
• Micronutrients: Address specific micronutrient deficiencies (e.g., Zinc, Iron, Boron) identified by soil tests through basal application (e.g., Zinc Sulfate at 10-15 kg/ha within 10 days of transplanting) or foliar sprays.

4. Biofertilizers:

Biofertilizers contain beneficial microorganisms that enhance nutrient availability and uptake.

• Azolla: Cultivate Azolla in rice fields as a green manure, capable of fixing atmospheric nitrogen (up to 30 kg N/ha).
• Blue-Green Algae (BGA): Inoculation with BGA can fix atmospheric nitrogen, particularly in waterlogged conditions of rice fields.
• PSB (Phosphate Solubilizing Bacteria): Inoculation with PSB (e.g., Bacillus megaterium) helps in solubilizing insoluble soil phosphates, making them available to plants.
• Potassium Solubilizing Bacteria (KSB): KSB helps in mobilizing soil potassium.
• Seedling Root Dip: Dip rice seedlings in a slurry of Azotobacter and PSB before transplanting to promote initial root development and nutrient uptake.

5. Water Management:

Efficient water management, particularly controlled irrigation, can significantly improve nutrient use efficiency and reduce nutrient losses (e.g., intermittent irrigation helps manage zinc deficiency). Maintaining a water level of 2-5 cm until 3-4 weeks after transplanting is crucial.

6. Crop Rotation:

Integrating legumes into crop rotation (e.g., rice-legume rotation) can improve soil nitrogen status and overall soil health, reducing the need for external nitrogen inputs for subsequent rice crops.

By synergizing these components, INM for transplanted rice aims to optimize nutrient supply, reduce environmental impact, and achieve sustainable high yields.