To bolster food security in a warming world, engineers are developing a coating that could better protect seeds, such as beans, from drought in semiarid regions. The coating mimics a mucilage-based hydrogel produced naturally by some seeds, such as basil and chia. The hydrogel traps moisture, regulates nutrient retention, and creates an environment around the seed which promotes the growth of beneficial microorganisms. The artificial coating is accordingly tailored to help protect seeds during germination and early seedling growth. In semiarid regions, water stress caused by a lack of available moisture during these sensitive periods of a plant's development is the highest cause of crop loss worldwide. This water stress on agricultural crops in drought-prone, marginal lands is expected to substantially increase in coming decades because of global climate change. See also: Agricultural engineering; Drought; Farm crops; Global climate change; Mucilage; Seed
The artificial coating is a two-layered biopolymer, or biological polymer. The inner layer consists of silk combined with the sugar trehalose and also contains rhizobacteria, which are microorganisms that colonize plant roots and symbiotically provide plants with nutrients. The outer layer, composed of pectin (a polysaccharide) and carboxymethylcellulose (a cellulose gum), swells and helps retain any available water. Importantly, all the materials used in making the coating are readily available, inexpensive, biodegradable, and can work with any kind of seed. Applying the coating involves dipping and then spraying seeds—a simple process that farmers could handle themselves on-site at a farm. However, the most economical approach is likely to be through centralized, facility-based processing. See also: Biopolymer; Fertilizers and nutrient management; Pectin; Rhizosphere; Rhizosphere ecology; Root (botany); Silk; Symbiosis
In a case study on an experimental farm with semiarid, sandy soil in Morocco, the researchers covered common beans (Phaseolus vulgaris) with their artificial drought-resistant coating. Plants that grew from the coated beans experienced improved health compared to control groups, with greater root mass, stem height, and chlorophyll content, among other metrics. North Africa is just one of many regions in which farmers working semiarid lands are expected to be impacted by global climate change. Other such regions around the world include the Sahel—a 200-km-wide (125-mi-wide) transition zone between the Sahara Desert and wetter regions to the south in Africa—as well as swathes of Central and South Asia, Australia, the Rocky Mountain region in North America, and central South America. The research team is now conducting field tests to follow the beans through a growth cycle all the way until harvest to determine if yields are ultimately improved as expected. See also: Bean; Desertification; Experiment
