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Notes on Role of Manures and Fertilizers in Crop Production

Notes on Role of Manures and Fertilizers in Crop Production

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  • Manures are plant and animal wastes used as a source of plant nutrients.
  • They release nutrients after decomposition.
  • Manures are categorized as bulky organic manures and concentrated organic manures.
  • Examples of bulky organic manures include FYM, compost, night soil, sludge, sewage, and green manures.
  • Concentrated organic manures include oilcakes, blood meal, fishmeal, and bone meal.
  • Fertilizers are industrially manufactured chemicals containing plant nutrients.
  • Fertilizers have higher nutrient content compared to organic manures and release nutrients almost immediately.
  • Three groups of fertilizers: Straight fertilizers (single nutrient), Complex fertilizers (two or more nutrients), Mixed fertilizers (two or more nutrients).

Role of Manures and Fertilizers:

  • Organic manures improve water holding capacity in sandy soil.
  • They enhance aeration and root growth in clayey soil.
  • Organic manures add plant nutrients, including micronutrients, essential for plant growth.
  • Increase microbial activity, aiding in nutrient release.
  • Organic manures require incorporation before sowing due to slow nutrient release.
  • Fertilizers supply essential nutrients in large quantities to crops.
  • They are readily utilized by plants directly or after rapid transformation.
  • Fertilizer dose can be adjusted based on soil testing.
  • Balanced nutrient application is possible by mixing appropriate fertilizers.

Agronomic Interventions for Enhancing Fertilizer Use Efficiency (FUE):

  • Using the best fertilizer source depends on crop, variety, climate, soil condition, and availability.
  • Examples of fertilizer sources for different nutrients are provided:
    • Nitrogen: Ammoniacal or Nitrate
    • Phosphorus: Water soluble or Citrate soluble
    • Potassium: Muriate of potash
    • Sulphur: Sulphate or Elemental S
    • Multinutrient fertilizers: MAP, DAP, SSP, Nitrophosphates
    • Multi-nutrient mixtures: Various NPK combinations
    • Fortified fertilizers: Neem-coated urea, Zincated urea, Boronated SSP, NPKS mix.
  • Adequate fertilizer rates are essential, diagnosed using various methods:
    • State recommended generalized fertilizer dose or blanket recommendation
    • Soil-test based fertilizer recommendations
    • Soil-test crop response based recommendations
    • Plant analysis for diagnosing nutrient deficiencies
    • Chlorophyll meter and Leaf colour charts, etc.

Balanced Fertilization:

  • Balanced fertilization involves adequate supply of essential nutrients, proper application methods, timing, and nutrient interrelationships.
  • Adequate supply of all essential nutrients is essential to avoid deficiencies in secondary and micro-nutrients.
  • Experimental results show that adding minor quantities of micro-nutrients (about 20-25 kg or two foliar sprays) can increase crop yields by up to 20%.
  • Proper methods for applying nutrients include broadcasting, band placement, and foliar sprays, depending on the nutrient and soil type.
  • Timing of nutrient application varies according to the crop's physiological needs.
  • Upland crops typically require two splits of fertilization (seeding and 3-5 weeks after the first dose).
  • Flooded rice usually requires three splits (transplanting, 3 and 6 weeks after the first dose).
  • Nutrient interrelationships should be considered to avoid antagonistic effects.
  • Excessive application of certain fertilizers, like 120 kg P ha-1, can lead to imbalances and reduced crop yields and quality.

Integrated Nutrient Management:

  • Integrated nutrient management involves blending organic sources (manures, crop residues, green manures, bio-fertilizers) with inorganic fertilizers to meet crop demands.
  • Efficient use of available organic sources reduces the need for inorganic fertilizers.

Utilization of Residual Nutrients:

  • Efficient utilization of crop residues involves understanding climatic conditions and carry-over effects.
  • Proper blending of residues in cereal-legume rotations is important.
  • Mixing shallow-deep rooted crop rotations helps utilize residual nutrients effectively.


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