Issue Date: May 2017
To ensure optimal crop growth, spreading suitable agricultural waste around the crops, known as soil mulching, creates favorable conditions for crop growth and soil moisture retention. Agricultural wastes such as straw, rice husks, banana leaves, coconut fiber waste, and corn stalks have been traditionally used as mulch.
In recent times, synthetic fiber materials like plastic films have completely revolutionized the benefits of mulching. Using plastic films as mulch prevents surface water runoff, controls water evaporation, and prevents the upward movement of salts. This helps reduce water loss and soil erosion.
History and Development of Soil Mulching:
Paper mulch was first introduced in 1920. However, due to the cost, labor, and mechanization requirements, it was not commercially viable for vegetable crops. In the early 1960s, along with the development of paper mulch, studies were conducted using polyethylene films. The introduction of mechanized soil mulching in 1960 marked significant progress in agriculture.
Advantages of Plastic Mulch:
- Completely prevents water infiltration, reducing direct evaporation of soil moisture and preserving soil humidity.
- Controls the upward movement of salts by reducing water evaporation.
- Prevents the leaching of nutrients mixed with water away from the plant roots.
- Non-transparent films help control long-term weed growth.
- Maintains soil temperature, aiding in crop growth and quick seed germination, especially during night and cold seasons.
- Controls weeds in seedling nurseries.
Plastic mulch creates a micro-climate beneath it, promoting increased carbon dioxide production from microbial activity, enhancing photosynthesis in plants. Complete soil cover prevents direct impact from raindrops and soil erosion, maintaining soil structure. Plastic mulch is more durable than other materials.
Disadvantages of Plastic Mulch:
- Cost is significantly higher compared to agricultural waste mulches.
- Using black films can cause young plants to wilt and burn due to excessive heat.
- Challenging to apply and requires care due to potential issues with pests like rodents and dogs, and in some areas, snakes.
Benefits of Plastic Mulch:
- Maintains soil moisture in rain-fed lands.
- Reduces irrigation frequency in irrigated lands.
- Modifies soil temperature to suit crops.
- Controls weeds and enhances crop yield.
- Prevents soil erosion and controls soil-borne diseases by increasing soil temperature.
- Increases overall yield.
Types of Mulch Films:
Since 1960, various plastic films have been used for mulching, primarily low-density polyethylene and high-density polyethylene films. Polyethylene absorbs solar radiation and emits long-wave radiation, warming the soil and creating favorable conditions for crop growth. Today, primarily low-density films are used.
Characteristics of Mulch Films:
- Thickness: The film’s weight affects its cost, so thin films are preferred for agriculture but must be durable. Initially, 60.76-micron (240-300 gauge) thick films were used, which were expensive. Modern technology has produced 10-micron films, significantly reducing costs but making them prone to tearing.
- Width: Depends on crop row spacing, typically ranging from 1 to 1.5 meters. Wider films can be heat-expanded as needed.
- Perforations: Depending on conditions, choose perforated or non-perforated films. Non-perforated films reduce water stagnation and ensure even fertilizer distribution, but perforated films are better for areas with high rainfall.
- Color: Affects soil temperature, air temperature around the crops, and soil salinity. Black films prevent water evaporation and salt accumulation, ideal for weed control. Gold or light yellow films attract pests.
Selecting Mulch Films:
Choose films based on crop needs, the season, and the purpose of mulching. For rainy seasons and high rainfall areas, use perforated films. For fruit orchards and plantations, use thicker films. Use black films to heat soil and control pests, yellow or gold films to attract and control pests, thin films to speed up seed germination, and white films for summer crops.
Application Methods for Mulch Films:
Apply films on the soil surface during low wind conditions. Ensure the films are tight without wrinkles or slack. Edges should be buried 7-10 cm deep at a 45-degree angle. For pre-planting mulch, perforate the film according to crop spacing, then spread it on the soil. After planting, bury the edges 10 cm deep in the soil.
Precautions When Applying Plastic Mulch:
Do not fix the film too tightly to the soil; allow some slack to accommodate thermal expansion and contraction. For black films, leave more slack due to higher expansion and contraction. Do not apply the film during periods of high heat.
Removing Mulch:
Post-harvest, removing mulch, especially from large areas, can be challenging. Developed countries use various methods to manage this. Some films are designed to degrade after a specified period (60, 90, 120, or 150 days) under sunlight. However, remnants buried in soil may resurface during plowing, causing issues. Research continues to find solutions for this problem.
Dr. M. Rajasekar, K. Govindan, S. V. Kotteeswaran, Precision Farming Development Center, Agricultural Engineering College, Tamil Nadu Agricultural University, Coimbatore – 641 003.
