Chapter 1 | Unit I - Manures, Fertilizers and Soil Fertility Management


Fertilizers and Soil Fertility Management

Chapter 1-
Introduction & importance of organic manure


Organic manures, which are natural products, are utilized by farmers to support sustainable crop growth. There are a variety of organic manures available, including farm yard manure, green manures, compost made from crop residues and other farm wastes, vermicompost, oil cakes, and biological waste such as animal bones and slaughterhouse refuse.

The term "manure" originally meant that which was "worked by hands", but gradually came to apply to any process which can improve the soil. Soil organic carbon plays a key role in the nutrient cycling of soil and is also valuable for attaining sustainability.

The crop removes large quantities of plant nutrients from the soil, particularly the removal of NPK nutrients at the present level of crop production has been estimated at 125 kg/ha/annum whereas the annual addition is not more than 75 kg resulting in the depletion of the nutrient reserve of the soil. 

Using too many chemical fertilizers and not using enough natural, organic sources of nutrients can damage the soil and make it hard for farmers to grow crops consistently. This can lead to soil health problems.

Soil organic matter is the key to soil fertility and productivity. In the absence of organic matter, the soil is a mixture of sand, silt, and clay. Organic matter makes the soil healthier and helps living organisms grow. Even though we know how helpful organic matter is for the physical, chemical, and biological properties of the soil, it is not used enough in modern farming.

The regular recycling of organic waste to the soil is the best way to keep the right amount of organic matter in the soil. Recycling organic matter in the soil should become a regular feature of modern agriculture. In traditional agriculture, followed over generations in India, the use of plant and animal wastes as a source of plant nutrients was the accepted practice. Using organic manures and green manure crops are not considered important enough in modern farming practices.

Importance of organic manures:-

1. Organic manure helps to maintain the structure of soil by forming groups of soil particles called aggregates, which makes it lose and easy to work with. Water infiltrates and percolates more readily. The granular condition of the soil maintains favorable conditions of aeration and permeability.

2. It increases the water-holding capacity of the soil. Organic matter helps soil hold more water, especially in sandy and loamy soils. Soil with more organic matter is also better at absorbing and retaining water than soil without it.

3. Surface runoff and erosion is reduced by organic matter as there is good infiltration.

4. Using organic matter or organic manure on the surface of the soil can help prevent soil loss due to wind erosion.

5. Covering the surface of the soil with coarse organic matter (mulching) can keep the soil cooler in the summer and warmer in the winter. It also helps to reduce the amount of water lost through evaporation.

6. Organic matter is a source of energy for the microorganisms that live in the soil.

7. Organic matter is a storage of chemical elements that plants need to grow. 
Organic matter contains most of the soil's nitrogen, as well as significant amounts of phosphorus and sulfur. As it breaks down, it releases these nutrients, as well as hormones and antibiotics, to help plants grow.  Organic manure also provides all the necessary nutrients for plants but in limited amounts.

8. Newly added organic matter can help make phosphorus more accessible in acidic soils.

9. Organic acids produced from breaking down organic matter can help lower the pH of alkaline soils.

10. Newly added organic matter provides food for soil life such as earthworms, ants, and rodents. These organisms help improve soil drainage and air circulation. Earthworms can only thrive in soils that have enough organic matter.

11. When organic matter breaks down, it creates organic acids and carbon dioxide that help dissolve minerals like potassium and make them more accessible to plants.

12. Humus (highly decomposed organic matter) stores exchangeable cations like potassium, calcium, and magnesium. Humus also helps keep ammonium fertilizers from washing away by holding them in a form that can be easily taken up by plants.

13. Organic matter can help stabilize the pH and chemical reactions in the soil by functioning as a buffer (act as a buffering agent).

14.  Due to an increase in biological activity, the nutrients that are in the lower
depths are made available to the plants.

15.  It improves the physical, chemical, and biological properties of the soil.

16. It helps in maintaining the C: N ratio in the soil and also increases the fertility
and productivity of the soil.

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