How does high content of organic matter in soil enhances its water holding capacity and plant nutrition?
Yes, particularly in coarse- (sandy) and medium textured soils. Anyway, the effect of organic matter is positive in majority of mineral soils. In all soil it enhances biological activity. The clayey soils with higher organic matter content require less strength for tillage and have better water filtration. On the other hand , there may exist certain excess of organic matter in mineral soils (about 5-6% or more, as in Poland) which indicates certain water excess and, consequently - shortage of air. However, this excessive content of organic matter is a result, and not a cause of excess of water.
A high content of organic matter in soil enhances its water-holding capacity and plant nutrition through several mechanisms:
1. Increased Water Retention
2. Improved Soil Structure
3. Nutrient Retention
4. Slow release of nutrients
5. Microbial activity
6. pH buffering
In summary, a high organic matter content in soil creates a favorable environment for plant growth by enhancing water retention and nutrient availability while promoting healthy soil microbial activity.
Organic matter causes soil particles to bind and form stable soil aggregates, which improves soil structure. With better soil structure, water infiltration through the soil increases and improves the soil's ability to absorb and hold water as well as reduces the potential for surface crusting of the soil. Increased levels of organic matter and associated soil fauna lead to greater pore space with the immediate result that water infiltrates more readily and can be held in the soil. If we make the assumption that organic matter holds 10 times its weight, or 82,026 kg (180,836 lbs) of water. There are 8.3454 lbs in a gallon, so that is 21,668 gallons of water. Soil organic matter significantly improves the soil's capacity to store and supply essential nutrients and to retain toxic elements. It allows the soil to cope with changes in soil acidity, and helps soil minerals to decompose faster. Organic manure application enhances organic matter content, and better soil structures retain more water, improving soil water retention capacity. That is roughly 1.5 quarts of water per cubic foot of soil for each percent of organic matter, according to Sullivan in "Drought Resistant Soil. Improving water infiltration and retention capacity through high levels of organic matter and permanent soil cover, such as cover crops or mulch, which substantially reduce the amount of water needed for irrigation.
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