Importance and application of plastic mulch in agriculture and horticulture
Hamid Larijani, faculty member of Islamic Azad University, Varamin Branch
Content of this article
- Introduction
- Benefits of plastic mulch
- Types of plastic mulch
- Mulching machines
- Conclusion
Introduction
We have heard many times that the largest volume of water is consumed in agriculture and with the water crisis, all eyes are turned to the most important axis of the country’s development, namely agriculture. In recent years, many farmers have abandoned farming or farming due to water shortages and migrated to cities, or live on the minimum. Therefore, preventing agricultural activities to reduce water consumption does not make sense at all. What is certain is that food production inside the country should continue, but along with management issues such as changing planting patterns, watershed management, municipal wastewater treatment, etc., the use of technology solves many problems.The use of low tillage implements, pressurized irrigation systems, greenhouse cultivation, the use of superabsorbents, growth regulators and other technologies can undoubtedly ensure the continuity of production for years to come. And now how much attention has been paid to these cases and to what extent they have been used has a place among the Arabs! But one of the simplest methods of cultivation, including farms, gardens and greenhouses, is the use of mulch in agriculture.Mulch or mulch is a coating on the soil surface that prevents weeds from growing and moisture from evaporating. The use of plastic mulch, which began in the 1950s, is a solution that solves a number of problems in agricultural production. Today, in large food-producing countries, plastic mulch plays an important role in agriculture. In China, for example; Land cultivated with plastic mulch has increased from 120,000 hectares in 1982 to more than 20 million hectares in 2011 (Wenquing et al., 2014).Unfortunately, despite the widespread acceptance of this technique by Iranian farmers, there are no statistics on the area under plastic mulch cultivation in the country. However, the many benefits of mulching have led farmers to creatively and traditionally use plastic mulch to produce plants such as cantaloupe, melon, watermelon, tomato, eggplant, lettuce and cabbage.
Benefits of plastic mulch
Maintain soil moisture:
It can be said that this is the most important advantage of plastic mulch and the main reason for its development in arid regions of the world. Covering the soil with plastic prevents moisture from leaving and water vapor returning to the soil in drops. According to Hatami et al. (2012) Plastic mulch reduced water consumption in tomato production by 28 to 41% and increased yield by 21%. In saline soils, preventing water evaporation prevents the increase of surface soil salinity.Creative farmers make the most of their water share by covering plots or climates and ridges in traditional irrigation. But the use of plastic mulch in combination with drip irrigation not only significantly reduces water consumption but also dramatically increases water use efficiency. Obviously, the presence of constant moisture around the roots and the plant does not face dehydration stress helps to optimize nutrient uptake and plant growth.In this method, irrigation tape or 16 mm pipes and droppers are placed under the plastic. Planting all row plants including vegetables and summer, legumes, corn and all trees, especially trees in dry areas such as pistachios, pomegranates and grapes with plastic mulch is possible and is common in many parts of the world and has high quantitative and qualitative performance.
Weed control
Mulches reduce weeds in two ways; Preventing light from reaching the soil and thus reducing the germination and seedling growth of weeds as well as a physical barrier against the growth of weed seedlings grown under plastic (Ngouajio and Ernest, 2004). In experiments Ragablarijani et al. (2012), black plastic mulch led to a 92% reduction in weeds. Preventing the growth and growth of weeds also reduces water wastage by them.
Soil heating and product maturity
The passage of light through clear plastics causes direct heating of the soil and also traps energy through the greenhouse effect. In addition, on the outer surface of the plastic, the air around the plant is heated and provides suitable temperature conditions for faster plant growth. All this leads to early ripening of the product and coincidence of harvest at a reasonable price in the market.In addition to the mentioned benefits, keeping the fruit clean, reducing fruit spoilage, preventing tuberculosis and erosion are other benefits of mulch.
Types of plastic mulch
Plastics are classified in the market in terms of color and thickness. Clear and black colors are the most common. Clear plastic allows light to pass through and causes the soil to heat up quickly, but weeds grow under the plastic and lift or puncture the plastic (especially perennials such as Aviarslam and Qayaq). In contrast, black plastic prevents the growth of weeds and, of course, absorbs heat and transfers it to the soil through displacement.Other colors, such as blue and red, also have advantages, such as the reflection of blue and red light into the canopy and behind the leaves and increase photosynthesis, but are less commonly used. The use of double-sided plastics such as white or silver on black has also been considered in hot areas and seasons, as the white surface reflects light and prevents overheating of the soil, and the black surface controls weeds.Plastics in terms of thickness are produced from 6 microns to 150 microns depending on the plant growth period and the required durability. The plastics used by Iranian farmers are generally 30 microns thick and between 60 and 220 centimeters wide.Unfortunately, in Iran, due to the lack of complete familiarity of many plastic producers and farmers, they all use the same color and thickness for all plants. Obviously, for a plant like eggplant that has been on the ground for at least 8 months, thicker plastic with anti-UV should be used. Recently, our research group succeeded in using 150 micron white on black plastic, which was designed and produced by Yazd Plastic Chemical Company, in Dasht-e Safaieh Company, Semnan, for pistachio trees, which has remained completely healthy for the past three years due to soil and saline water. The region showed good results compared to the control. These results are promising that this type of mulch can be used for planting seedlings in poor lands (saline and dry) for fruit trees as well as desertification and soil stabilization.
Mulching machines
For various reasons, including lack of government support, the private sector is reluctant to manufacture or import mulching machines, and farmers traditionally use plastic mulch manually. Newer mulching machines, on the other hand, do all the work, including preparing the bed, laying the irrigation tape, pulling the plastic, and even drilling and planting seeds and seedlings. There is no doubt that training and promotion of mulching technique, production of various types of mulch plastics and supply of related machines, considering the numerous benefits of plastic mulch, can strengthen the continuity of cultivation, employment and domestic production. Therefore, the formation of a specialized mulching working group in the Ministry of Agriculture can facilitate and accelerate the achievement of the above goals.
Conclusion
Critics of plastic mulch criticize environmental pollution and the destruction of plastic fields. However, if used correctly and the appropriate material and thickness are selected based on the plant growth period, the plastic can be collected and recycled at the end of the period. In recent years, biodegradable plastics have been introduced into the market, which are made from vegetable starch and, like disposable vegetable containers, are degraded by microorganisms after degradation and become part of the soil.
Sources
– Hatami, S., A. Nourjou, M. Henareh and L. Pourakbar, 2012. Comparison effects of different methods of black plastic mulching and planting patterns on weed control, water-use efficiency and yield in tomato crops. Int. J. Agric. Sci., 2: 928-934.
- Ngouajio M. and Ernest J. 2004. Light transmission through colored polyethylene mulches affected weed population. HortScience, 39(6): 1302-1304.
– Rajablarijani HR, Mirshekari B, AghaAlikhani M, Rashidi V, Farahvash F. 2014. Sweet corn weed control and yields in response to sowing date and cropping systems. Hortscience. 49(3):289–293.
-Wenquing et al. 2014. Plastic-film mulch in Chinese agriculture: Importance and problems. world agriculture.