The Magic of Soil
Few people would be able to guess the subject that many researchers are calling one of today’s most exciting scientific frontiers. The frontier is microscopic: it’s the space between plant roots and soil, a space that researchers are starting to realize is one of the most dynamic interfaces on earth! A dazzling complexity of activities and interactions take place in this soil/root space and the emerging understanding of what is going on could be a key to enhancing plant productivity in the future.
The star actors are an overwhelming number of bacteria, fungi and other small animals that (especially in natural ecosystems) form a line of defense against soil-borne plant pathogens and that also facilitate plant nutrition in many wonderful ways. One well understood example involves fungi and bacteria that live near plant roots and provide nitrogen and phosphorus to the plant, getting carbon in exchange. Yet another set of bacteria and fungi can provide iron to the plants, and in an even more fascinating three-way relationship, there is a fungus that is a pathogen of an insect, but can also live on plants and transfer nitrogen from the insect to the plant!
A recent review of work in this area called the soil a “microbial seed bank.” If farmers could only understand all the different factors that affect the soil biota, perhaps they would not need to use as many chemical fertilizers and pesticides. Protecting and enhancing these underground activities might be a more effective approach.
Because most crops grown on farms have been developed in mono-cropping systems with plenty of fertilizers and in the absence of soil-borne pathogens, the resulting varieties perform best in those nutrient-rich environments and may have lost some of their age-old ability to benefit from soil microorganisms to get nutrients and to repel diseases. In organic agriculture, where nutrients are often provided in more complex, “natural” forms, and few pesticides are used, the increasing attention to this soil/root space (also called the rhizosphere) is a welcome development. Perhaps if there were more plants that had been developed by plant breeders specifically with organic systems in mind, we would see enhanced performance?
The sustainability of agriculture depends in part upon the reduction of inputs of mineral nutrients and pesticides. Organic farmers would welcome more research into the selection and cultivation of plants that take advantage of the ‘microbial seed bank.’ While organic farmers have always tried to encourage “living soils” and enhance natural microbiological cycles, it would be a paradigm shift if all of agriculture started to collaborate with the untapped work force that exists in the soil.
~ Judith Redmond
