Wax-coated sand to replace plastic mulch in fields

Farmers often place plastic sheets on the ground along their crop rows to help maintain moisture in the soil. However, according to a new study, using wax-coated litter could be cheaper and more environmentally friendly.

Plastic mulch, often used with buried irrigation pipes, effectively reduces the amount of water that evaporates from the soil. But unfortunately, covering entire plots with new sheets of this material every year can be expensive.

Additionally, the small pieces of plastic break down and remain in the environment, while the rest often ends up in a landfill after the growing season is over.

Thus, a team from the King Abdullah University of Science and Technology (KAUST) in Saudi Arabia, led by Associate Professor Himanshu Mishra, is studying an alternative: silica sand coated with purified paraffin.

The scientists first prepared the material by first dissolving the wax in a hexane solvent, mixing the sand into this mixture and allowing the solvent to evaporate. Thus, a layer of hydrophobic (water-repellent) wax 20 nanometers thick remained on each grain of sand; It should be noted that the process has been refined to the point that no solvent is needed.

When the resulting superhydrophobic sand (SHS) was spread in a thin layer in a field in Saudi Arabia, it was found to reduce soil moisture loss by 56-78%.

Additionally, when SHS was used for multiple growing seasons as a 5-10 mm thick mulch for wheat, barley and tomato plants, these plants produced up to 73% more grain and fruit than a group of control plants grown on bare ground. ground. Additionally, the number and diversity of beneficial soil microbes at the crucial root-soil interface did not appear to be affected by the presence of SHS.

While paraffin wax isn’t particularly eco-friendly in its usual form, Mishra told us that the purified “food-grade” wax used by her group is non-toxic and non-biodegradable, so it shouldn’t harm to the environment or harm the environment. accumulate there.

Depending on the thickness of the wax layer and the environmental conditions, SHS degrades over time under microbial action at the soil-SHS interface. In our experiments, the SHS lost its water repellency in about nine months, which means that the SHS grains lost their waxy coating. Once plowed, they simply incorporated themselves into the sandy soil like a drop in the ocean. Thus, in our environmental conditions, successive cultivation cycles with SHS do not cause wax accumulation.

Himanshu Mishra

More information: acs.org (English text).

Via www.acs.org

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