Soil temperature greatly influences how well plants and microorganisms (and therefore the entire soil community) thrive. Organisms that live in the soil depend on consistent soil temperatures that maintain constancy – or at least that don’t experience drastic changes. With our warming climate, some scientists have expressed concern over how rising soil temperatures might impact plant reproduction and survival.
"Most plants are sensitive to extreme changes in soil temperature," said Samuel Haruna, a researcher at Middle Tennessee State University. "You don't want it to change too quickly because the plants can't cope with it." The seeds of some plants will fail to germinate if soil temperature changes occur too rapidly; others, meanwhile, will die because their roots cannot function well. Compacted soil such as those subject to farming, and soils lacking moisture (like many soils are during climate change-induced droughts) are particularly vulnerable to temperature changes. Because of this, Haruna and colleagues have been working to figure out if perennial biofuel and cover crops could alter soil thermal properties.
To determine this, the researchers cultivated several types of cover and perennial biofuel crops in a field and later analyzed the soils ability to regulate temperature. (The cover crops they used included cereal rye (Secale cereale), hairy vetch (Vicia villosa subsp. villosa), and Austrian winter pea (Pisum sativum subsp. Arvense); the perennial biofuel crops were giant miscanthus (Miscanthus × giganteus) and switchgrass (Panicum virgatum)). After collecting soil sample at 10 cm depth increments (until 30 cm deep), the team looked at the samples’ soil thermal properties including thermal conductivity, volumetric heat capacity, thermal diffusivity, volumetric water content, soil organic content, and bulk density.
Their results showed that both perennial biofuel and cover crops protect soils against extreme temperatures, acting as a buffer by slowing down how quickly temperatures spread through the soil. “Their roots break up the soil, preventing soil molecules from clumping together and heating or cooling quickly. The roots of both crops also add organic matter to the soil, which helps regulate temperature,” writes Science Daily.
The perennial biofuel and cover crops help twofold by retaining moisture as well, which also helps to buffer quick temperature changes. In addition, the cover crops add nutrients to the soil, which makes other crops more productive and profitable for farmers. Though the researchers have yet to move past laboratory testing, Haruna hopes that his work will encourage farmers to invest in cover crops.
"Climate change can cause temperature fluctuations, and if not curtailed, may affect crop productivity in the future," he said. "And we need to buffer against these extreme changes within the soil."