Mulch Magic: White Plastic's Cooling Effect On Soil

Plastic mulches have been used for over six decades to modify the radiation budget, decrease soil water loss, and regulate soil temperature, water use efficiency, plant growth, yield, quality, and weed and insect infestation. The use of white and reflective films can lower the maximum temperature experienced by the soil, while black and clear films increase average temperatures, enabling earlier germination and longer growing seasons. In this context, it is worth investigating how much white plastic mulch lowers soil temperatures.

White plastic mulch lowers soil temperature by reflecting sunlight

Plastic mulches have been used in crop production systems for over six decades. They are easy to implement, but proper selection and installation are critical to their success. One of the main purposes of using coloured plastic mulches is to modify the radiation budget and decrease soil water loss. They also help regulate soil temperature, water use efficiency, plant growth, yield, quality, and weed and insect infestation.

The effects of mulch films on soil temperature are considered the most important way in which the use of mulch impacts crop yield. Mulch films adjust the energy flow in the soil, allowing different parts of the incident solar spectrum to penetrate and reach the soil. While black and clear films generally increase average temperatures relative to bare soil, enabling earlier germination and longer growing seasons, white and reflective films can lower the maximum temperature experienced by the soil.

In a study in Central Ontario, it was found that when the uncovered soil temperature was high enough to prevent growth or damage plants, the mulch films reduced that threat. The rows covered by white-on-black films, which provided the least warming relative to the uncovered soil, had temperatures that were as much as 8 °C lower than the uncovered soil at the hottest times of the year. This prevented the soil temperature from exceeding the maximum temperature tolerable for the growth of onions, broccoli, and carrots.

The effects of white plastic mulch on soil temperature vary by region and crop

The use of plastic mulches in agriculture has been a useful technology for specialty crops for over six decades. They are easy to implement, but proper selection and installation are critical to their success. Plastic mulches are available in many colours, including black, clear, silver reflective, and white. Each colour has a different effect on soil temperature, and these effects vary by region and crop.

In general, black plastic mulch is widely used in spring and late fall to warm up the soil. The black plastic absorbs the energy from the sunlight and transfers the heat to the soil through conduction. This can be an effective way to improve crop performance in warm-season vegetables when soil temperatures are variable. However, high temperatures on the surface of black plastic mulch can cause damage to transplants, reduce germination, and kill plants. In onions, black mulch can cause damage to bulbs due to excess heat. In tomatoes and peppers, high soil temperatures under black mulch can lead to fruit quality issues.

White plastic mulch, on the other hand, can be used to lower soil temperatures. The white mulch reflects solar radiation, cooling the surface and the soil beneath. This can be particularly useful in the middle of June when days are longer and air temperatures are higher, and for crops planted in July and August. White mulch can increase transplant survival and germination, especially in seeded crops. In a study in Central Ontario, Canada, white-on-black mulch films reduced soil temperature by as much as 8 °C compared to uncovered soil at the hottest times of the year.

The effects of plastic mulch on soil temperature can also vary depending on the type of crop and the region. For example, research by Shah Jahan et al. found that black plastic mulches resulted in higher temperatures than olive, silver, white, and blue mulches. However, Ibarra-Jime´nez et al. reported that brown and blue plastic mulches had higher soil temperatures than black mulches. These variations are likely due to differences in soil type and climatic conditions. Additionally, the use of mulch films can adjust the energy flow in the soil, allowing different parts of the solar spectrum to penetrate and reach the soil. This can impact the maximum temperature experienced by the soil and influence crop yield.

Overall, the effects of white plastic mulch on soil temperature vary by region and crop. While it can be effective in lowering soil temperatures in certain contexts, proper selection and installation are critical to its success. Other factors, such as soil type, climatic conditions, and crop-specific considerations, also play a role in the effectiveness of plastic mulches.

White plastic mulch reduces the need for irrigation and protects against frost

Plastic mulch has been used for over six decades to aid in crop production and landscaping. It is a useful technology for specialty crops, and its proper selection and installation are critical to its success. White plastic mulch, in particular, has been found to reduce the need for irrigation and protect against frost.

White plastic mulch reflects most of the sunlight back into the atmosphere, resulting in minimal energy absorption and heat transfer to the soil. This keeps the soil cooler than bare ground or clear, black, or coloured plastic mulch. As a result, white plastic mulch can help protect against early frost and high temperatures.

The insulating properties of white plastic mulch also contribute to its ability to reduce the need for irrigation. It reduces heat loss at night, keeping the soil warmer than other plastic mulches or bare ground. This stabilisation of soil temperature and moisture suggests a reduced need for irrigation and protection against frost.

Additionally, white plastic mulch can help conserve water by reducing evaporation and erosion. It acts as a barrier, preventing water from evaporating from the soil surface and keeping the soil moist. This, in turn, decreases the plant's requirement for higher irrigation.

The use of white plastic mulch in conjunction with drip irrigation further enhances water conservation. Drip irrigation applies lower amounts of water directly to the root zone, reducing the amount of water needed and decreasing leaching of fertilizers. This combination of white plastic mulch and drip irrigation can lead to improved water use efficiency, as seen in studies with potato plants.

White-on-black mulch is the most common type of mulch

The impact of polyolefin-based agricultural mulch films (including clear, black, and white-on-black films) on soil temperature and moisture content was studied over a 4-month period in central Ontario, Canada. The study found that all mulch films demonstrated a qualitatively similar ability to insulate the soil from extremes in both temperature and moisture, suggesting a potentially reduced need for irrigation and protection against early frost, high temperatures, overwatering, and drought. In the rows covered by white-on-black films, which provided the least warming relative to the uncovered soil, the soil temperature was as much as 8 °C lower than in the uncovered soil at the hottest times of the season.

The effects of mulch on soil temperature vary depending on the type of mulch and the specific crop and soil type. For example, a research report by Shah Jahan et al. indicated that higher temperatures were recorded by black plastic mulches than olive, silver, white, and blue. In contrast, Ibarra-Jimenez et al. reported that brown and blue plastic mulches had higher soil temperatures than other mulches, including black. The variation is due to differences in soil type and climatic conditions. Confirming this, reports indicated that black plastic mulch is more effective in increasing the minimum, maximum, and mean soil temperature than white/black, aluminium/black plastic mulching systems.

The use of plastic mulch has been a useful technology for specialty crops for over six decades. However, proper selection and installation are critical to its success. For example, good heat transfer starts with proper soil preparation, ensuring that all organic matter is turned over and that there are no clumps on or near the surface. These clumps can interfere with the tight contact of the plastic mulch with the soil, which is necessary for optimal heat transfer. In addition, the amount, type, and rate of plastic mulch use should be carefully considered, as the negative impact of plastic ruminants on soil aeration, physical and chemical properties can be detrimental to soil biota, mainly soil microorganisms.

White mulch increases germination and crop survival

The use of mulch films is an important means by which the impact of mulch affects crop yield. Mulch films adjust the energy flow in the soil, allowing different parts of the incident solar spectrum to reach the soil and preventing the loss of lower-energy infrared radiation. White mulch films can lower the maximum temperature experienced by the soil, which is useful when the uncovered soil temperature is high enough to prevent growth or risk damage to plants.

White mulch films can lower bed temperature by up to 20°F. The use of white mulch increases germination and survival of seeded crops. This is especially useful in the case of crops seeded through black mulch, where germination is often reduced and plants that do emerge can be killed by the excess heat. White mulch can also help prevent fruit quality issues in tomatoes and peppers, as well as damage to bulbs in onions, that can be caused by the high temperatures of black mulch.

The use of white mulch is recommended for crops planted in July and the first half of August, as well as in the middle of June when days are longer and air temperatures are higher for longer periods of time. In the second half of May and the beginning of June, black mulch is preferred as it helps warm the soil and get warm-season vegetable plants off to a good start. Past research has shown that using white mulch during this period can reduce crop performance in warm-season crops.

The proper selection and installation of plastic mulch are critical to its success. Good heat transfer starts with proper soil preparation, ensuring that all organic matter is turned over and that there are no clumps on or near the surface. The use of coloured plastic mulches can help modify the radiation budget, decrease soil water loss, regulate soil temperature, and improve water use efficiency, plant growth, yield, and quality. However, it is important to consider the amount, type, and rate of use of plastic mulches as they can have a negative impact on soil aeration, physical and chemical properties, and increase insect pest attacks in some crops.

Frequently asked questions