Plasticulture: Paving the Way for Agricultural Innovation | The Overview

Plasticulture is a farming technique that has been gaining popularity among farmers worldwide. This innovative method involves the use of plastic materials to improve crop production and protect plants from adverse environmental conditions. Developed in the mid-20th century, plasticulture has revolutionized the way modern agriculture is practised, making farming more efficient and sustainable.

What is Plasticulture?

Plasticulture is a farming technique that involves using plastic materials such as mulch films, drip irrigation lines, and greenhouse covers to improve crop production and protect plants from environmental conditions. Plastic originated from the Greek words “PLLASSIEN” and “PLASTIKOS” meaning to shape a soft substance temporarily and permanently. Plastic consists of a variety of polymers having different properties. 

There exist natural polymers but only synthetic polymers are called plastics. Plasticulture is defined as the use of synthetic polymers in agriculture. Plastics are used in high-tech horticulture techniques such as drip irrigation, plastic mulches, and in post-harvest techniques. This practice is also known as plastic mulch farming, and it has been gaining popularity among farmers all over the world.

History of Plasticulture

Polyethene polymers were discovered in the late 1930s and introduced as plastic mulch in the mid of 1950s when Dr Emery.M.Emmert of the University of Kentucky recognized the use of low–density polyethene (LDPE)  and high-density polyethene (HDPE) as plastic mulch. Now plastics are used as plastic mulches, and plastic films, in drip irrigation systems.

Later the discovery of other polymers such as polyvinyl chloride, polypropylene and polyesters and their use in row covers, fertigation equipment, fittings and connectors, revolutionized the production system in agriculture. In the 1960s first commercial plastic mulch was introduced in the United States. Since then, plasticulture has evolved and become a widely adopted practice in many countries.

Types of Plasticulture Techniques

There are various types of plasticulture techniques used in agriculture, including

1. Plastic mulching 

Mulch is a defensive covering between the soil surface and the environment. The energy-radiating behaviour of mulch depends on its colour and has an effect on the microclimate of plants. It determines the temperature of mulch and its underlying soil. Three colours of mulches predominate in vegetable production systems namely white, clear and black. 

2. Black plastic mulch 

The soil temperature under a plastic mulch depends upon the thermal properties such as reflectivity, absorptivity, and transmittance of mulch. Black plastic mulch is an opaque material that absorbs mostly UV, visible, and infrared wavelengths coming from the sun and radiates absorbed energy in the form of longer-wavelength infrared radiation.

Most of the absorbed solar energy of the black plastic mulch is lost in the atmosphere through radiation and forced convection.  If there is a good contact of plastic mulch with soil it can transfer a large proportion of energy to the soil by conduction. The temperature of mulched soil in the daytime is 5°F (2.8 °C) higher at 2 inches (5 cm) depth and 3°F (1.7°C) higher at 4 inches (10) depth as compared to bare soil. Black plastic mulches are used in vegetable production systems.

3. Clear plastic mulch 

Clear plastic mulches absorb little solar radiation and transmit 85 to 90% of solar energy but these properties depend upon the thickness and degree of opacity of plastic. The lower side of the plastic mulch is covered with condensed water that is transparent to coming shorter wavelengths but is opaque for outgoing longer wavelengths, so the energy loss in bare soil is retained in clear plastic mulch.

In clear plastic mulch, the temperature of the soil in the daytime is 8 to 14 °F (4.4 to 7.8 °C) higher at 2inches (5cm) and 6 to 9°F (3.3 to 5°C) higher at 4inches (10cm) depth as compared to bare soil. Clear plastic mulches are used in cooler regions.

4. White plastic mulch 

White, white on black, or silver reflective mulches result in a slight decrease in soil temperature 2°F (1.1°c) at 1 inch (2.5cm) or 7°F (4°C) at 4 inches (10cm) depth as compared to bare soil. These mulches are used to establish crops like cauliflower or tomatoes in mid-summer when a decrease in soil temperature is beneficial. 

5. Wavelength-selective mulches

There are some wavelength-selective mulches that transmit selective wavelengths. These mulches absorb photosynthetically active radiations. The colours of these mulches are blue green and brown, these mulches warm up the soil without considering the weed problem. There are some other colours such as red, blue, green, and yellow coloured mulches that reflect different radiation patterns into the plant canopy and may affect photosynthesis and result in plant morphogenesis and early yields. 

Advancements in Drip Irrigation

In the 1970s, drip irrigation systems were developed, allowing farmers to deliver water directly to plants’ roots through a series of plastic tubes and emitters. This greatly improved water efficiency, as well as saved time and labour.

The controlled distribution of irrigation water and nutrients to the root zones of plants using a network of pipes at regular intervals through drippers is termed drip irrigation. Drip irrigation improves crop quality, and early crop maturity, saves 40 to 70% of water, controls weeds, and saves 30% fertilizer, and 10 % labour cost, also helps in efficient fertigation, disease control, uses of saline water, eliminates soil erosion and suitable for uneven lands. 

The most important features of polyethene in a drip irrigation system are rust resistance, UV resistance, compensation of pressure range, fracture-resistant and easy rollback. High-density polyethene (HDPE) is used in drip irrigation units. The thickness of sub-lines and lateral lines ranges from 0.5 to 2.0mm. 

Tunnels and greenhouses

A high tunnel is a plastic-covered structure constructed directly over the soil for growing plants. A low tunnel is a small structure that covers a single bed or row. Tunnels provide a protected environment to grow plants from severe weather, buffer low temperatures and reduce certain disease and pest attacks. It helps to extend growing seen along with increasing yield and quality and shelf life of crops.

High tunnels also help to grow farmers’ income by giving out-of-season crops at premium prices. High tunnels have gained attention as they help to increase the availability of fresh fruits and vegetables. Tunnels act as a physical barrier for pest and insect entry, reducing pest and insect attacks but this only happens during cold seasons when the sides of tunnels are closed. But not valid during growing seasons when the sides are open for proper ventilation. 

Greenhouses are framed structures in which plants are cultivated in partly or completely controlled environments. It has played a significant role in better space use, and production of crops in severe weather and regions with heavy rainfall. Green Houses plastic sheets act as selective radiation filters. 

The greenhouse and tunnels have almost similar benefits and effects, except that in tunnels crops are grown directly on soil and in the greenhouse, plants are grown in pots. 

Propagation and Nursery Management in Plasticulture

Plastics are used in layering and uniting techniques. In uniting polyethylene strips are used to interface stock and scion. In the layering system, different shaded poly coverings are utilized. Blue, red and dark poly-coverings resulted in higher rates in roots and endurance through etiolation impact, expected for cell division and development. 

In nurseries, plastics are used as sacks, plug plates, hanging plastic pots, nursery bags, portrays, crates, sprays, mini and micro-sprinklers, drip irrigation systems, low tunnels, shaded net houses, greenhouses etc. plastics are used in nurseries for early and healthy saplings for off-season crops. It reduces the mortality rate of seedlings and improves the germination of seeds.

Packaging 

High-density polyethene (HDPE), low-density polyethene (LDPE), polypropylene (PP), linear low-density polyethene (LLDPE), and polyamide (PA) are used as product bundling in agriculture. Plastic bundling is lightweight, adaptable, cost proficient, sterile, visible from an external point of view, easy to print, reusable, and extends the time frame of useability of an item.

Plastics are used in the development of bundling materials, for example, adaptable plastic movies, plates with rape, net pack, froth sleeves, and container, development of conservation, transportation, and handling of natural products. 

Sleeving

Sleeving is a technique using a 16 to 18-micron-thick cylindrical plastic bag open from both sides to protect bananas, from rain, wind, hail, dust, pests, and other elements. It is used when the fingers begin to curl upward. Sleeving shields the skin of the fruit from leaf bug and bird damage and also improves fruit colour, fruit becomes more consistent and bigger. 

Advantages of Plasticulture

1. Earlier and higher overall yields

The use of plastic in horticulture increases the earliness and total crop productivity of high-value horticultural crops. Secondly, it also gives the advantage of out-of-season production of crops like cucumber, pepper, brinjal, melon etc. 

2. Soil fumigation or solarization

It is a hydrothermal method of cleansing soil in moist soil that is covered by mulch films and greenhouses and exposed to sunlight during the hot summer months. Plasticulture improves plant growth by improving soil structure, colour, temperature and moisture, and improves seed germination. It sanitizes the soil and is used for nematode control.

3. Protection against weeds, pests and diseases 

Black plastic mulches do not allow light to enter and inhibit the growth of weeds. Some weeds are hosts of some pests when that specific weed reduces then its pest attack also decreases. Mulches act as physical barriers and don’t allow insect pests to enter the covered part of the field. As the mulches increase the soil temperature is at a certain level at which some pathogens can’t survive. This is sometimes a very cheap method that doesn’t use chemicals and any specialized techniques to deal with insect pests and weeds. 

4. Water conservation and high WUE 

Mulches are very effective in conserving and retaining soil water in areas where the rate of evaporation exceeds the rate of precipitation. It acts as a physical barrier to escape water into the atmosphere. In mulching, irrigation water is applied directly to the roots of plants instead of overhead sprinkler irrigation or flooding, plastic film mulching conserves water and increases the water use efficiency of crops.

5. Soil conservation

Plastic film mulching protects soil from erosions such as wind and water erosion. A mulched soil is protected from direct contact with rain, hail, and even human and animal traffic. It keeps soil loose and well aerated, reducing chances of compaction which in turn helps roots to grow with efficient uptake of nutrients and water use.

A healthy root system produces a healthy shoot system. The nitrogen content in mulched soil is higher than in bare soil due to the least nutrient leaching and enhanced mineralization. Plastic film not only conserves soil but also improves its chemical, physical and biological properties. 

6. Microbial diversity 

Plastic films increase the biodiversity of microbes, colonization of roots, spore density and structure of community species of arbuscular mycorrhizal fungi. The increase in microbial community is attributed to temperature rather than any other factor. 

7. Better micro-environment for the crop

Clear plastic mulch increases the temperature of the soil as it transmits most of the solar radiations similarly white plastic mulch reflects solar radiations and is used to decrease the temperature in hot areas. Plastic mulch can make a better microenvironment by not allowing soil compaction, efficient water utilization, and prevention of nutrient leaching.

8. Elimination of root pruning 

Cultivation is eliminated in mulched fields except the area between mulched beds, this reduces the pruning of roots. 

9. Cleaner product 

The edible portion of the plant is cleaner and less prone to rot as the soil is not splashed on the fruit due to the presence of mulch. 

10. Gas exchange 

Carbon dioxide is released from the roots of plants and the decomposition process can’t be released from mulched soil and accumulates beneath the mulch. As mulch does not allow carbon dioxide to be released it has to escape through the holes punched for the plants. This is called the “chimney effect” It results in a higher concentration of carbon dioxide near actively growing leaves near the transplant holes. 

11. Ability to double / triple crop

Once the first crop has been harvested the second crop could be grown on the same mulch. It reduces the expenses and the second crop is obtained from the previous mulch and drip irrigation system.

Economic Impacts of Plasticulture

Plasticulture economically impacts the agriculture industry in several ways. The use of plastic mulch significantly increases crop yields, leading to higher profits for farmers. This is because plastic mulch creates a more favourable environment for plant growth by conserving soil moisture, controlling weeds and pests, and increasing soil temperature. plays a significant role in the agriculture industry. Plasticulture, which refers to the use of plastics in agricultural practices, has allowed for increased efficiency and productivity in crop production.

However, there are also economic considerations that must be taken into account when implementing plasticulture practices.

How Plasticulture is Economically for Farmers

Plastic mulch is a cost-effective solution for weed control, as it reduces the need for manual labour or expensive herbicides. This translates to cost savings for farmers, as they spend less on weeding and can allocate resources towards other aspects of their farm operations.

Moreover, plastic mulch also helps in reducing water usage by up to 70%, resulting in lower irrigation costs for farmers. This is especially beneficial in areas where water scarcity is a concern, as it allows farmers to grow crops with less water and potentially expand their crop cultivation.

In addition, plastic mulch can extend the growing season for certain crops by maintaining warmer soil temperatures. This means that farmers can produce multiple harvests in a year, leading to greater profits.

Disadvantages of Plastic Mulches 

Plastic has a number of uses and benefits in agriculture, but it also results in a number of pollution hazards. Making its “white revolution” into “white pollution”

Removal and disposal of plastic mulch 

Polythene mulch is made up of non-renewable, petroleum-based materials, and is not easily degradable. After the use of plastic mulch, its removal is not easy as its crumbs remain in the soil that pollutes it. The disposal of plastic mulch ends up in dumping and open burning that release CO, CO2, and greenhouse gases such as methane, and ethylene into the environment. 

Change in Soil physical and chemical properties 

Application of plastic films can have severe effects on soil, sometimes due to reduced evaporation the soil becomes ultra-damp which provides favourable conditions for some microorganisms such as fungi to cause disease. The most problematic aspect is residual plastic films which can alter soil physical and chemical properties such as porosity, bulk density, structure, movement of water and nutrients which directly or indirectly affect plant health and yields.

Biodegradable Plastic Mulch (BDMs)

To reduce negative environmental problems caused by persistent plastic waste biodegradable plastic mulches have been developed that provide sustained and environmentally friendly solutions for agricultural activities. Biodegradable plastic mulches are designed to be tilled into soil after crop removal. BDMs’ common polymers are polylactic acid, starch, cellulose, and polyhydrooxyalkalinaoates (PHA).

Effects of biodegradable plastic mulch

• BDMs have caused an increase in microbial biomass, enzyme activities, respiration and changes in soil microbial community.
• Increased fungal abundances in the soil as a result of BDM incorporation.
• Evidence of enhanced degradative activities by soil microbes suggests that BDMs may ultimately change carbon cycling and storage in soil. The total amount of carbon in BDMs is small, and much of it is expected to be respired as CO2. 

Use of Precision Farming in Plasticulture

Precision Farming in Plasticulture is an innovative technology that enables farmers to use precise techniques and methods to manage their crops and soil. This technique integrates high-tech sensors, GPS mapping, and data management systems to provide accurate information about the crop’s growth stages, nutrient levels, water levels, soil moisture content, and other factors. The goal of precision farming in plasticulture is to minimize the use of resources such as water, fertilizers, and pesticides while maximizing crop productivity.

One of the main advantages of using precision farming in plasticulture is that it allows farmers to have a better understanding of their crop’s needs. With the help of data collected from various sensors, farmers can accurately determine the amount of water, fertilizers, and pesticides needed for each section of their field. This not only reduces the risk of over or under-application but also saves resources and reduces costs for the farmer.

Moreover, precision farming in plasticulture also helps farmers to identify any potential issues or problems in their fields. By continuously monitoring the crop’s growth and health, farmers can detect early signs of diseases, pests, or other factors that may affect their yield. This allows them to take immediate action and prevent further damage

Environmental Impact of Plasticulture

Plasticulture has significantly impacted the environment in both positive and negative ways. On one hand, it has allowed for increased food production, reduced labour costs, and improved crop yields. However, on the other hand, it has also contributed to various environmental issues that need to be addressed. to the use of plastic materials in agriculture, which includes mulching films, drip irrigation systems, greenhouse covers and more. While plasticulture has brought many benefits to modern farming practices, it also has a significant impact on the environment.

Positive Impacts

Plasticulture has greatly aided in increasing agricultural productivity and efficiency. The use of plastic mulch has allowed for better weed control, reduced soil erosion, and improved water conservation. This has enabled farmers to produce higher yields with less labour and resources. Furthermore, the use of plastic covers in greenhouses has extended the growing season, allowing for year-round production of crops. This has been especially beneficial for regions with harsh climates.

Negative Impacts

Despite its benefits, plasticulture has also contributed to negative environmental impacts. The use of plastic materials in agriculture has led to an increase in plastic waste, which is not biodegradable and takes hundreds of years to decompose. This results in the accumulation of plastic debris in landfills and natural habitats, causing harm to wildlife and ecosystems.

Moreover, the production of plastic materials for agriculture requires fossil fuels, which contributes to greenhouse gas emissions and exacerbates the issue of climate change. In addition, improper disposal or incineration of plastic materials can release harmful chemicals into the environment, further damaging ecosystems.

Solutions

To address these negative impacts, there have been efforts to develop more sustainable alternatives to traditional plasticulture practices. Biodegradable mulch films made from natural materials such as starch, cellulose and sugar-based polymers are being increasingly used. These materials break down into organic matter in the soil, eliminating the need for plastic waste disposal.

Furthermore, there is a growing trend towards using recycled plastics in agriculture, reducing the demand for new plastic production. This not only helps reduce plastic waste but also reduces the carbon footprint associated with producing new plastic materials.

Additionally, proper waste management and recycling programs can help decrease the amount of plastic waste generated from agricultural practices. Education and awareness campaigns can also encourage farmers to adopt more sustainable practices and reduce their environmental impact.

Conclusion 

The development of polythene as a plastic film and its subsequent use in agriculture has revolutionized the commercial production of vegetables. Due to its not degradative properties plastic has become a major polluting agent. There is a need to develop new techniques for the proper use and disposal of plastic to reduce its detrimental effects on agricultural soils and the environment.

There should be more research on biodegradable plastic mulches to investigate its impact on soil and microbial community for sustainable agriculture as well as draw a flow chart indicating its proper installation to disposal technologies.

Faiza Waseem

University of Punjab, Faculty of Agricultural Sciences, Lahore