White plastic mulch in high and low trellis improves light microclimate, growth, ecophysiological and biomass parameters, and production in hops under tropical conditions climate
This study demonstrates that using white plastic mulch in both high and low trellis systems significantly enhances light reflection, physiological performance, and biomass production of hops grown in tropical climates, thereby improving the crop's viability outside its native temperate regions.
Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer
Hops are the flowers that give beer its signature bitterness and aroma, a crucial ingredient that breweries cannot replace. For centuries, these plants have been grown in the cool, temperate climates of the Northern Hemisphere, where the weather naturally suits their needs. However, as the global demand for beer grows, scientists and farmers are asking if these temperate plants can thrive in hotter, tropical regions. The challenge lies in the light. Hops are climbing vines that need a lot of sunlight to grow tall and produce flowers, but in the tropics, the sun is intense and the heat can stress the plants. Furthermore, the lower parts of the plant often sit in shadow, missing out on the energy they need to grow. Researchers are now exploring whether simple changes to how the ground is covered or how the vines are supported can create a better environment for these plants in warmer climates.
In a recent study conducted in the tropical state of Rio de Janeiro, Brazil, a team of scientists tested a specific idea: could reflecting sunlight back up into the lower parts of the hop plant help it grow better? They focused on a popular variety called 'Yakima Gold' and set up an experiment to see how two different ways of managing the soil and the vines would affect the plant's health. The researchers compared two types of trellises, or supports for the vines: a traditional tall, vertical setup and a lower, horizontal one. They also compared two types of ground cover: leaving the soil bare versus covering it with a sheet of white plastic. This white plastic acts like a mirror, bouncing sunlight that would otherwise be absorbed by the dark earth back up toward the leaves.
The team measured how much light actually reached the lower branches of the plants throughout the day. They found that the white plastic cover made a dramatic difference. In the plots with the white plastic, the amount of light bouncing up into the lower canopy increased by 66 percent compared to the bare soil plots. This extra light did not just sit there; the plants responded to it immediately. The hops grown with the white plastic and the reflective light grew significantly taller and produced much more total plant material. Specifically, the plants with the white plastic were 40 percent heavier in total biomass than those on bare soil. The flowers, or cones, which are the valuable part of the crop, also saw a boost, with production increasing by 34 percent in the white plastic treatments.
Beyond just getting bigger, the plants became more efficient at their daily work. The researchers measured how the leaves breathed and processed energy, looking at how much carbon dioxide they took in and how much water they released. The hops with the white plastic cover took in more carbon dioxide and opened their leaf pores wider to let that gas in, which is essential for growth. They also released more water vapor, a sign that they were actively cooling themselves and moving nutrients through their system. This increase in activity happened even though the plants were growing in a hot, tropical climate where such stress is common. The study showed that by simply changing the ground cover, the researchers created a better microclimate that allowed the plants to function more like they would in their native cool regions.
The study also looked at the color and health of the leaves using special sensors that measure how light bounces off the plant surface. The plants with the white plastic cover had greener leaves, indicating they had more chlorophyll, the green pigment that captures sunlight. This extra greenness meant the plants were better equipped to use the reflected light to fuel their growth. Interestingly, the way the vines were arranged on the trellis mattered less than the ground cover. Both the tall vertical supports and the low horizontal supports worked well when paired with the white plastic, suggesting that the key to success in the tropics was the light reflection rather than the height of the structure.
While the plants grew faster and produced more, the study also noted a trade-off regarding water. The plants with the white plastic used water more freely, releasing more of it through their leaves to support their rapid growth and cooling. In contrast, the plants on bare soil were more conservative with their water, holding back slightly more, but this caution came at the cost of slower growth and fewer flowers. This suggests that in a tropical environment where water is available, the best strategy for hops is to maximize light and growth rather than trying to conserve every drop of water. The research concludes that using white plastic mulch is a practical and effective way to help hops adapt to tropical climates, offering a promising path for growing this temperate crop in new, warmer parts of the world.
Drowning in papers in your field?
Get daily digests of the most novel papers matching your research keywords — with technical summaries, in your language.