Why is Soil Organic Matter (SOM) so important to soil fertility and plant growth?
The effect of SOM on soil fertility far exceeds its percentage share of the soil volume. Organic matter affects soil fertility and productivity in many ways: • It promotes soil structure improvement by plant residues and humic substances leading to higher WHC, better soil aeration and protection of soil against erosion. • It influences nutrient dynamics, particularly: nutrient exchange, thus keeping the nutrients in available forms and protecting them against losses; • nutrient mobilization from decomposed organic nutrient sources: N, P, S, Zn, etc.; nutrient mobilization from mineral reserves by complex formation or by changes in pH and redox potential; • immobilization of nutrients on a short-term or long-term basis (reverse of mobilization); nutrient gain as a result of N fixation from the air.
