Sustainable Hemp Farming: Are U.S. Growers Doing It All Wrong?

The hemp industry has experienced significant growth since the Farm Bill’s passing into law in December 2018. The legislation made it federally legal to grow industrial hemp, which contains less than 0.3% THC by dry weight, in 46 states in America. At the time of writing, Mississippi, Idaho, New Hampshire, and South Dakota have banned hemp cultivation. With no legal ramifications for farmers in the other 46 states, we may now see a golden age of hemp growing.

Hemp Farming in the U.S.

In the 1930s, hemp looked like it would become a billion-dollar crop until the Marihuana Tax Act of 1937 put an end to its cultivation. According to Successful Farming magazine, America aimed to have 100,000 to 200,000 acres for hemp production in 2019. However, in reality, seed supply limited overall production.

Hemp is grown very differently depending on what industry it is supplying. Farmers growing hemp for CBD will have a maximum of 1,600 plants per acre. Hemp grown for bioplastics and textiles has up to 400,000 plants per acre! Hemp for mass-market products grows tall, and farmers harvest the tops for seeds and use the stalk for various industrial purposes.

Experts believe that up to one million acres will be used for hemp within five years.

Experts believe that up to one million acres will be used for hemp within five years. Sales of hemp reached more than $1 billion in 2018, and that was before it became fully legal to grow! American farmers are turning to hemp as a money crop. A decent yield of food-grade hemp can yield up to $750 per acre. Compare that to soybeans, which offer a $150 profit per acre.

The ongoing trade war with China is hurting American farmers. This dispute is yet another reason why so many are flocking to the new hemp industry. When grown responsibly, hemp is a sustainable crop. However, the continuing use of plastic mulch is in danger of transforming a ‘green’ industry into an environmentally harmful one.

What Is Plastic Mulch?

Mulching is an effective method of protecting and insulating a plant’s delicate root systems against inclement weather conditions. It improves the nutrient profile of the soil, helps it retain more moisture, and reduces erosion. Growers have the option of using organic and inorganic mulch.

Organic mulch is great for the environment and contains biodegradable materials. Some of these include dried leaves, straw, wood chips, and grass clippings.

Inorganic mulch involves the use of materials such as crushed gravel, stone, and river rock.


However, plastic mulching has become extremely popular in hemp farming. That’s terrible news for the environment. It is classified as an ‘inorganic’ mulch and involves using polyethylene to shield plants from the weather.

This form of mulching gained popularity in the 1950s, and its use was widespread in commercial vegetable and berry production. Typically, the polyethylene film is a thin black plastic sheet. It reduces moisture evaporation, prevents soil erosion, and insulates the soil.

There is also a clear polyethylene sheet used in plastic mulching. The dark sheet is preferred for warming up the soil, preventing weed growth, and retaining the soil’s moisture.

The clear film can promote faster growth in early spring. It also does an excellent job of warming up the soil. However, the black sheet is preferred because it is better for stopping weed growth. Proponents of plastic mulch point out its benefits, which include the following:

Better Soil Structure

Plastic mulching traps moisture and heat, which prevents the loss of nutrients. Also, you can see the black sheeting, which ensures no one walks into the garden.

Soil Insulation

Certain plants, such as vegetables, don’t handle the cold of winter too well. The same is true for hemp seedlings and immature hemp plants. The polyethylene film helps retain heat, and the plastic mulch heats the soil by around five degrees Fahrenheit.

Weed Control

Weeds are bad news for any garden, but plastic mulch effectively suppresses weed growth in a large space. By installing polyethylene sheets, you prevent weeds from getting the sunlight needed for photosynthesis, which will kill them.

Faster Growth & Better Crop Quality

Hemp is a seasonal crop when grown outdoors. However, if you use plastic mulching, you can grow your plants earlier in the season. As it warms up the soil, it enables you to plant your hemp crop up to three weeks earlier. Those who use plastic mulch also say it provides better quality crops by preventing the growth of diseases and rot.

Reduces Root Damage Risk

When you use polyethylene sheets, you don’t need to disturb your garden, barring incursions between the plastic rows. When plants can grow in undisturbed soil, the plant roots can grow and spread into the ground deeply.

Cultivation causes root damage, but most gardeners have no choice as they want to deal with weeds. If you have a weed-free garden, you can leave your plants in peace and reduce the risk of root damage.

What Does the Research Say about the Agricultultural Impact of Plastic Mulch?

Several studies have looked at the effect of plastic mulch on agriculture in China.

A study by Gao et al. published in Science of The Total Environment in February 2019 is one such example. The researchers discovered that plastic mulching increased crop yield in China by 24%. The sheeting also boosted water use efficiency by 27%. Another example is a study by Liu et al. published in Environmental Research Letters in September 2014. The authors found that plastic mulching increased grain yields by 20-35% and cash crop yields by 20-60%.

By 2011, China used 1.25 million tons of plastic film, covering around 20 million hectares of land. Unfortunately, these increased yields come at a high cost to the environment.

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In both studies, the researchers pointed out the need to improve plastic film standards to control pollution. They also said that large amounts of the residual plastic film have detrimental effects on water, nutrient transport, and soil structure.

The plastic revolution has taken hold in the United States as well. The use of plastic mulching is so widespread that it is called ‘plasticulture.’

In 2015, the Modern Farmer journal lamented the growth of an industry that was already worth $5 billion. The publication suggested it would be worth double that by 2020.

Why Plastic Mulch Is Slowly Ruining the Environment

Large scale hemp farmers are now using plastic mulch instead of its biodegradable equivalent. Hemp is supposed to be a sustainable crop. However, using an environmentally hazardous material like plastic mulch makes it unsustainable.

Climate change has a myriad of potential effects, including heavy rainfall and arid soil. Higher atmospheric temperatures lead to more arid soil, with our plant life in danger of suffering severe water stress. Hot air holds more vapor, so moisture that should remain stored in the soil instead forms clouds. The result is torrential rainfall that damages crops and leads to erosion.

Some believe that there are 55,000 tons of used agricultural plastic sitting in Florida’s dumpsites and landfills.

Plasticulture proponents champion it as a possible solution to water shortages and the problem of feeding our expanding population. Alas, plasticulture causes immense pollution. Some believe that there are 55,000 tons of used agricultural plastic sitting in Florida’s dumpsites and landfills. There are dumpsites so large that you can see them from the Kennedy Space Center!

Plastic mulch is also expensive, and at the end of each growing season, the mulch is pulled up and taken to a dumpsite. Despite it being a valuable resource, the plastic is taken to South America and burned. It is a congealed natural gas with an energy density greater than gasoline! The energy content of a pound of plastic mulch film is higher than a pound of coal.

The issue of whether plastic mulch is bad for the environment has been discussed for decades. In 2003, the United States Department of Agriculture looked at the material to decide if it was harmful or helpful. It wrote that plastic mulch increases surface runoff from rainfall and irrigation. Bear in mind that large scale hemp growers possibly apply pesticide, which may runoff into nearby water supplies.

Overall, there are numerous downsides to using plastic mulch.

Plastic Mulch – An Environmental Disaster Zone

Removing the film from fields requires specialized equipment, and disposing of the plastic is difficult. Landfills tend to ask for more money to deal with plastic disposals. As a result, it is shipped overseas.

It isn’t biodegradable like organic mulch because it doesn’t break down completely. In the study by Liu et al., the authors explained that plastic film mulch was mainly composed of polyvinyl chloride. As a result, it doesn’t degrade in soil. While the film doesn’t degrade much, it could still produce harmful chemical products. Some of these include phthalate, ketones, and aldehydes.

The study claimed that large amounts of the residual film could result in unsustainable farmland and damage the agricultural environment. In China, excess levels of residual plastic film in the soil reduced cotton production by 15%.

Excessive Moisture

Plastic mulch traps moisture well and ensures that water doesn’t evaporate. However, too much moisture can be a bad thing as it makes it easier to overwater and drown the crops. Damp growing conditions may increase the risk of disease and infestation, which causes farmers to use pesticides!

Excessive Heat

While hemp is relatively durable, the same isn’t true for all crops. ‘Cool-season’ crops such as peas and lettuce could die from overheated soil.

Increased Salt Content in the Soil

In China, mulching for between 5 and 20 consecutive years resulted in a 122% to 146% increase in the topsoil’s salt content.

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Sustainable Alternatives to Plastic Mulch

For hemp cultivation to remain sustainable, farmers will need to cease using plastic mulch and opt for a biodegradable mulch instead. Thankfully, there are plenty of alternative mulching materials available, including:

Garden Compost: One benefit is that it helps to prevent weeds from growing. It also provides extra insulation during cold spells and ensures that hemp plants can access nutrients immediately.

Bark & Wood Chippings: This option looks aesthetically pleasing while surrounding your garden borders. Composted bark is a favorite of gardeners because it has a more natural look than bark chips.

Leaf Mold/Mushroom Compost: These options aren’t used that often. However, they can help provide the borders with lots of nutrients and ensure much-needed insulation during winter.

Straw: The straw’s scratchy surface keeps slugs at bay. It is popular amongst strawberry growers because it keeps the fruit away from the mud after heavy rainfall. You can use straw on top of another mulch to ensure moisture stays locked in.

The best time to apply the mulch is during the middle of spring until the beginning of the fall. The reason for this is that the soil is still warm. Non-biodegradable mulch options such as gravel, slate, and crushed seashells don’t offer much nutritional value, but they help conserve moisture.

Final Thoughts on Plastic Mulch in Hemp Farming

The cold, hard truth is that plastic mulching provides hemp farmers with several benefits. It can increase the overall yield and allow farmers to start growing earlier in the season. However, its use is causing an unsustainable level of environmental damage. Worse still, there are other viable, sustainable, biodegradable alternatives to plastic much such as compost and wood chippings.

Large-scale hemp cultivators use plastic mulch to maximize their profits; however, they do so at the environment’s expense. The question is, do these farmers want to prioritize short-term profits over long-term sustainable hemp farming? In other words, do they want to make more money now, or do they want to have a steady stream of income from sustainable hemp farming for generations to come?

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