Mycorrhizae are the almost-invisible fungi living in plant roots that increase plants’ ability to absorb soil nutrient minerals, including phosphorus, zinc and micronutrients. Along with bacteria, they recycle crop residue into nutrients, says Jill Clapperton, rhizosphere ecologist and agronomic consultant, Florence, MT.

An increase of 1% in soil organic matter (from crop residue or other sources) can increase its water-holding capacity by up to 16,000 gal./acre-foot, says Francis Yeatman, agricultural advisor, Integrations Farming Systems, Soil and Crop Nutrition,South Africa and Appropriate Technology Transfer for Rural Areas (ATTRA).  “Soils with adequate organic matter (3-6%) will have better structure and therefore water- and nutrient-holding capacity. Organic matter is a storehouse for plant nutrients and a very high capacity for holding cations as well as soil moisture. Because of its active holding sites it is also an important factor for determining herbicide selection and adjusting application rates.”