6. (c) Present a brief note on the types of mulches and their role in soil moisture conservation.

Types of Mulches

Mulches are broadly categorized based on their origin and composition, each offering distinct advantages and applications in agriculture.

1. Organic Mulches

These are derived from natural, biodegradable materials that decompose over time, enriching the soil with organic matter and nutrients.

• Crop Residues: Materials like wheat straw, paddy straw, maize stalks, and sugarcane trash. They are readily available on farms.
• Leaves and Grass Clippings: Fallen leaves and mowed grass provide excellent ground cover, though they decompose relatively quickly.
• Wood Chips and Bark: More durable and slower to decompose, suitable for perennial crops, orchards, and landscaping.
• Compost: A nutrient-rich mulch that significantly improves soil structure and microbial activity.
• Green Manures: Cover crops like clover or vetch, when terminated and left on the soil surface, act as living mulches initially and then decompose.

2. Inorganic Mulches

These are non-biodegradable materials that offer long-term benefits, primarily focusing on physical barrier properties.

• Plastic Films (Polythene Mulch): Available in various colours (black, clear, reflective silver) and thicknesses. Black plastic is highly effective for weed control and warming the soil, while reflective films can deter pests.
• Landscape Fabric: Permeable synthetic fabrics that allow water and air to pass through but suppress weeds.
• Gravel, Pebbles, and Stones: Used primarily in arid regions or for specific horticultural purposes to regulate soil temperature and prevent erosion.
• Rubber Mats: Often made from recycled tires, used in permanent plantings for durable ground cover.

3. Living Mulches (Cover Crops)

These are specific plant species grown alongside the main crop or during fallow periods to provide continuous soil cover.

• Legumes: Such as clover, vetch, and cowpea, which also fix atmospheric nitrogen, enhancing soil fertility.
• Grasses: Like rye or oats, that establish a dense ground cover.

Role of Mulches in Soil Moisture Conservation

Mulching plays a multifaceted role in conserving soil moisture, contributing significantly to improved water use efficiency in agriculture.

1. Reduction of Evaporation:
   • Mulch creates a physical barrier between the soil surface and the atmosphere, shielding the soil from direct sunlight and wind.
   • This barrier significantly reduces surface evaporation, a major cause of water loss, especially in hot and dry climates.
   • For instance, plastic mulches are highly impervious and prevent water and nutrients from passing through, effectively trapping moisture in the soil.
2. Improved Water Infiltration and Reduced Runoff:
   • Mulch layers protect the soil from the direct impact of raindrops, which can otherwise lead to soil compaction and increased surface runoff.
   • By slowing down the flow rate of rainwater, mulch allows more time for water to infiltrate the soil, thus increasing the availability of moisture for plant use.
   • Organic mulches, in particular, enhance soil structure over time, further improving infiltration rates.
3. Weed Suppression:
   • Mulch blocks sunlight, inhibiting the germination and growth of weeds.
   • Weeds compete with crops for vital resources, including soil moisture. By suppressing weeds, mulching ensures that available water is primarily utilized by the cultivated plants.
   • This reduces the need for chemical herbicides, promoting more sustainable farming practices.
4. Regulation of Soil Temperature:
   • Mulches act as an insulating layer, moderating soil temperature fluctuations. They keep the soil cooler during hot days and warmer during cold nights.
   • Maintaining a more stable soil temperature reduces the rate of moisture loss through evaporation and creates a favourable environment for root activity and water absorption.
   • Different colours of plastic mulch have varying effects; black plastic absorbs more solar energy, generally leading to higher soil temperatures compared to clear plastic.
5. Enhanced Soil Health and Water Holding Capacity:
   • Organic mulches decompose over time, adding organic matter to the soil. This improves soil structure, aeration, and its water-holding capacity.
   • A healthier soil structure allows for better water retention and reduces the risk of waterlogging.
   • Enhanced microbial activity, promoted by organic mulches, also contributes to a more resilient soil ecosystem capable of efficiently managing water resources.
6. Prevention of Soil Erosion:
   • Mulch covers the soil surface, protecting it from erosion caused by wind and water.
   • By preventing the loss of topsoil, which is rich in organic matter and nutrients, mulching helps maintain the soil's inherent ability to absorb and retain moisture.

The choice of mulch depends on factors such as crop type, climate, availability of materials, and economic considerations. For instance, plastic mulching is widely used in horticultural crops like tomato, chili, brinjal, and watermelon, especially when combined with drip irrigation systems, leading to significant water savings and increased yields. States like Rajasthan and Bihar offer subsidies for farmers adopting mulching techniques, acknowledging their role in enhancing agricultural productivity and water conservation.