Garden Plastic Mulch, Uses, Advantages, Disadvantages

Introduction to garden plastic mulch

Plastic mulch is considered as a type of inorganic mulch and this type of mulching utilizes polyethylene film to shield plants from the elements. Plastic mulching was used in commercial berry and vegetable plant production. Though, this method is now being adapted to home gardens too. The polyethylene film is usually a sheet of black plastic and then it works the same way as organic mulch; the film insulates the soil, prevents soil erosion, and reduces moisture evaporation.

A step by step guide to garden plastic mulch

Plastic mulches are used in conjunction with drip irrigation to maintain optimum soil moisture and for improved stand establishment. The main benefits of plastic mulch include increased and earlier crop yields. Plastic mulch can be used effectively to modify soil temperature levels. Black mulches intercept sunlight, which warms the soil. White or aluminum mulch reflects the sun’s heat and then keeps the soil cooler. Black mulch applied to the planting bed will warm the soil and promote faster plant growth in the early season, which generally leads to an earlier harvest. First harvest acceleration of about 7 to 14 days is not uncommon, depending on weather conditions. Clear mulch provides the greatest soil warming and useful in certain situations.

Plastic mulching in vegetable and fruit crops is covering the soil around the plant with plastics film, straw, grass, hay, dry leaves, and stones, etc which prevents the loss of moisture and acts as a barrier between the soil and atmosphere. It helps in moderating the soil temperature and micro-climate in the plant root zone, which helps to increase crop yield and early maturity of crops.

Basic types of plastic mulch used in the garden

There are mainly two basic types of plastic mulching: black polyethylene film and clear polyethylene. The black plastic film is ideal for eliminating weeds, warming up the soil during the cold season, and retaining the soil’s moisture. On the other hand, the clear plastic film works best for warming up the soil and encouraging faster plant growth early in the growing season. Clear plastic film isn’t as effective when it comes to suppressing weed growth.

Most commercial plastic mulches are made of linear, low-density polyethylene or high-density polyethylene. High-density polyethylene is lighter and also stronger than the same thickness of low-density polyethylene. Most plastic mulches vary in thickness from 0.75 to 1.5 mil and can be smooth or embossed. The diamond-shaped pattern on embossed plastics helps reduce contraction and expansion of the plastic mulch. Also, it is more resistant to wind fatigue and cracking. Plastics come in rolls about 2,000 to 4,800 feet long (depending on the thickness) and are 3 to 5 feet wide.

Black polypropylene mulches have been used in the greenhouse and nursery industries for some time as weed barriers. These ultraviolet, light-stabilized mulches are guaranteed to last up to 5 years. Then, they allow water and air penetration while controlling weeds. These tear-resistant mulches about 16 mil thick can be reused year after year. These mulches have been used to warm the soil, control weeds, harvest rainfall, and reduce evaporation of moisture from the soil.

Different colors of plastic mulch available for garden use

You can select from many different colors, including;

Black – The most widely used and inexpensive of the colored mulches, black plastic mulch has excellent weed suppression ability because of its opacity. It is useful for warming soil during the growing season, mainly if as much of the plastic as possible is in contact with the soil below.

White – The benefits of white plastic mulch in keeping weeds at bay, retaining soil moisture, and keeping the soil cool around the roots of crops such as peas, broccoli, cabbage, and cauliflower may be more easily and inexpensively achieved with a biodegradable mulch, e.g., straw. In cool climates with short growing seasons, white plastic mulch could not be a good idea. It can definitely help cool the soil in areas of extreme heat, smother weeds, and retain soil moisture and cooler soil temperatures. These effects make it possible to produce cooler weather crops such as cauliflower, cabbage, peas, and broccoli in warmer climates.

Brown – This Brown Infrared Transmitting (IRT) plastic mulch is a fairly recent innovation and it warms garden soil better than black plastic mulch early in the growing season.

Silver – Bell pepper plants produce significantly more fruit when planted using silver plastic mulch than when black plastic is used.

Blue – Blue plastic mulch is good to use when growing cucumbers, summer squash, and cantaloupe.

Advantages of plastic mulch in the garden

Using plastic mulch over soil keeps people from walking in the area, and preventing compacted soil. It warms the soil, keeps down evaporation, and virtually eliminates weeds.

Earliness and greater yields – Earlier plant growth and earlier crop production are two of the main benefits of using black and clear plastic mulches. Earlier crop production results in higher market prices and higher yields. Black plastic mulch can accelerate crop production as much as 1 to 2 weeks. Clear plastic mulch has been shown to increase earliness as much as 3 weeks in northern climates. Weed growth, however, can be the main problem under clear plastic unless appropriate herbicides or fumigants are used. Selecting the crop type (vine crops like pumpkins, squash, and melons) is important in warmer areas of the state for good ground cover or shading in the summer to prevent excessive heat buildup under the plastic.

Reduced evaporation – Plastic mulches mainly help reduce evaporation of moisture from the soil. Irrigation frequency and amounts generally can be reduced, although additional water can be needed to support earlier and greater crop production. More uniform soil moisture will result in less plant stress.

Improves soil structure – Using plastic mulching will help prevent soil from clumping together into a compacted mess. The material traps moisture and heat, this limits the loss of plant nutrients. Of all the mulching materials available on the market, plastic mulch is restrictive so it pairs well with a drip irrigation method. Also, the plastic film discourages people and pets from walking into the area, which further enhances the structure of the soil.

Insulates the soil – Most plants are temperature sensitive, vegetable plants, in particular, cannot stand the winter cold. One of the reasons why growers use plastic mulch is to help the soil retain heat as the cold months set in. Inorganic mulch like plastic mulch warms up the soil up to 5F. Plastic mulching regulates the soil temperature level evenly, insulating temperature-sensitive plants during the cooler months.

Weed control – Black plastic mulch prevents light from reaching the soil, growth of annual and most perennial weeds can be prevented. Thin black plastic mulch will not control nutsedge.

Improved quality – Plastic mulches help prevent fruit crops from touching the soil and thus reduce the incidence of fruit rots and keep fruit cleaner.

Reduced soil compaction and root pruning – The better weed control results in less cultivation and less root pruning. Undisturbed beds remain more friable with less compaction. Weeds between beds can be controlled with directed herbicides and by mechanical means.

Reduction in fertilizer losses – Flood and furrow irrigation methods tend to leach nitrogen and other water-soluble nutrients below the root zone. While plastic mulch techniques generally include drip irrigation, nutrient loss is kept to a minimum. Nutrients can be injected into the drip method and accurately delivered to the root zone as needed.

Insect control – In some cases, reflective silver and white plastic mulches help repel aphids and insects that damage plants and are vectors of viral diseases.

In case if you miss this: Terrace Garden Ideas, Tips for Design and Setup.

Disadvantages of plastic mulch in the garden

Removal and disposal – Removing the plastic mulch after the cropping season is the main disadvantage. The “tucks,” or sides of the mulch buried in the dirt, remain intact; they are not exposed to the sunlight and separate from the brittle mulch on the bed top. Little pieces of plastic mulch can scatter across a field. Many landfills will not accept plastic, and it is difficult to recycle. Photodegradable and biodegradable mulches have been evaluated, but results have been mixed. Another alternative is woven, black polypropylene mulch with an ultraviolet light inhibitor that can be reused for several seasons.

Cost – The cost of applying plastic mulch can be high both in terms of materials and equipment. The minimum equipment required includes bed-shaping equipment and a mulch applicator. Other equipment includes a drip-line applicator (usually associated with the mulch application) and a transplanter or seed planter. The advantages of using mulch for earliness, increased yields, reduced water application, better weed control and higher prices should offset the increased cost of using plastic mulches.

Management – With a drip irrigation system, managing plastic mulch is more intense. Wilting plants mean a plugged drip line, while overly wet areas could mean rodent damage to the lines. Dripline problems are hard to evaluate when covered with plastic mulch.

Plastic mulch can get too hot – While black plastic mulch is ideal for heat-loving vegetables like tomatoes, peppers, and melons, it isn’t suitable for those living in warm climates; the plants will get scorched. Plastic mulch is not appropriate for cool-season crops such as lettuces, peas, and root veggies because the soil warms too much.

Some applications of plastic mulch

Plastic mulch affected in soil preparation and fertilization

Plastic mulch is not a substitute for thorough soil preparation. A seed or transplanting bed prepared for mulch application should be the same quality as in non-mulched fields. The soil must be free of rocks, sticks, hard clods, and other materials that could puncture the plastic.

Rows must be laid off on widths compatible with available equipment. Then, the ability to work row middles is restricted with the use of plastic mulch due to mulch width. Rows on 6-foot centers covered with 5-foot wide mulch will have only 3 to 4 feet of free middle space, depending on the height of the bed and the amount of the mulch used for anchorage. Provisions should be made for weed control in the row middles, either with chemicals or mechanical cultivation.

Preplant fertilizer must be applied prior to mulch application. This means most of the potassium and phosphorus needs of the crop and part of the nitrogen. Fertilizer can be applied in a furrow prior to bedding or incorporated in the bed during the bedding procedure. The practice changes depending on the crop to be grown.

Weed control

Weeds cannot grow in darkness and black plastic covers these garden invaders, they die, and new weeds don’t sprout. Consequently, the best time for covering a vegetable bed in black plastic mulch is in the early spring season before the growing season starts. When the time comes to cut holes in the plastic to vegetables, any weeds that remained in the bed after soil preparation have died and won’t compete with young vegetable plants for water and soil nutrients.

Don’t forget, that weeds will grow in any areas the plastic mulch doesn’t cover. Weed shoots can appear in the holes where the vegetables were planted, and these must be pulled out by hand early in the season before they get established. Weeds can grow in the spaces between mulched beds. To prevent uncultivated areas from becoming overgrown and generating weed seeds, mow or hoe the weeds, spray herbicides, or spread organic mulch.

Soil moisture

Black plastic mulch conserves soil moisture by preventing it from evaporating. Only the exposed soils in the holes where the vegetable plants are growing lose water to evaporation. This means that more moisture is obtainable in the surrounding soil for plant roots, and you spend less time on watering the growing crops. On sandy soils where water is quickly lost, this is an important benefit, but it’s helpful during vacation periods when no one is around to water the garden.

Yet black plastic’s water conservation effect works the other way around. Rainfall and overhead irrigation system don’t penetrate the plastic, so the vegetable plants rely entirely on water supplied through other means. Remember to water the ground thoroughly before covering it in the plastic mulch at the beginning of the season. Then, water your crop after planting, install drip tape when you spread the black plastic, and then pour the water into the planting holes around the plants’ bases.

How to use plastic mulch in the garden

Step 1) While good at suppressing weeds and warming up garden soil, plastic mulch also makes an impermeable shield that traps air and water while potentially suffocating shallow-rooted plants such as shrubs. Because of this, it should be used on a short-term basis, on temporary crops such as vegetables, and must be removed at the end of the growing season or sooner, depending on its purpose. Available in clear and colored forms, different types of plastic mulch are correctly used for many purposes.

Step 2) Lay down clear plastic mulch over the soil before planting in early spring to warm the dirt or cover newly planted seeds to speed up seed germination in warm-season crops, which are peppers and melons; clear plastic can increase the temperature of the soil. Once the seeds have germinated, remove the plastic.

Step 3) Spread a single layer of black plastic mulch is the best plastic mulch at keeping weeds at bay over your garden soil to suppress weeds and grass and increase the soil temperature. In fact, if you grow warm-season vegetable crops with black plastic mulch, you’ll get higher yields.

Step 4) Tomatoes planted on black plastic mulch with tomatoes cages fastened to the earth with wooden stakes. Space the holes to fit the cages about 3 feet apart from center to center and place the plants where you want them and then transplant. Plant each tomato and then insert the label beside it in the hole.

Step 5) Roll out red plastic mulch around tomato plants to increase crop yield and reduce early tomato blight. Red mulch increases tomato yield by as much as 20 percent and increases strawberry and basil production. Also, use silver plastic mulch to deter aphids, whiteflies, and cucumber beetles.

In case if you are interested in Mulching Tomato Plants, Procedure, and Benefits.