Good farming practices are conducted for a variety of reasons. Farmers now include management practices such as over wintering cover crops, reduced tillage, and crop rotation with the goals of reducing soil erosion, managing nutrient availability, building soil organic matter, controlling weeds, and maintaining yields. What they may not know, and what was not considered when these practices were developed, was the role of soil biology in the success of these practices or the effect of these practices upon soil biology. An important component of the soil biological community is arbuscular mycorrhizal (AM) fungi. AM fungi form a mutualistic symbiosis with the majority of crop plants. Among the benefits to the plant ascribed to the symbiosis are enhanced: nutrient uptake, water relations, and disease resistance. Studies of the biology and function of these organisms help to answer the question: how are AM fungi impacted by, and what are their roles in the success of, these farming practices?
Results/Conclusions
Over wintering cover crops are planted to retain or replenish soil N, retard soil erosion, and compete with weeds. An added benefit is that they can act as host plants for AM fungi, and in so doing boost their populations. The cover crop provides host roots to colonize and from which to procure fixed carbon during what would otherwise be a bare fallow period for these obligate symbionts. Reduced tillage is increasingly practiced to enhance soil quality through reducing soil erosion and building levels of soil organic matter. It also enhances the dual functioning of the extra-radical phase of AM fungi as both the nutrient absorbing organ of the symbiosis and as an important source of inoculum for the new crop. Crop rotations combat yield decline in continuous monocultures, but also help guard against the characteristic of AM fungi that those that proliferate on a given host plant species are not necessarily those that enhance its growth. Therefore, understanding the soil biological underpinnings of farming practices can aide in their success and should be considered in developing the sustainable agricultural practices of the future.
