The size and arrangement of these aggregates influence the nutrient availability and drainage of the soil. Whether you have dry, sandy soil, silty soil or wet, heavy clay soil, adding organic matter in its many forms will improve the soil structure. Organic matter helps any soil become more like the ideal loamy soil. Microorganisms feed on organic matter and produce polysaccharides. Polysaccharides help form humus, which enables small clay or silt particles to stick together to form larger aggregates.
Larger aggregates create more pores for water and air to flow.
The soil drains better, the plants grow better because of the increased pore space and more nutrients are available. In sandy soils, humus acts like a sponge to catch and hold moisture. Humus also helps accumulate nutrients, making a sandier soil more fertile. It is measured on a scale of 1 to 14. The correct pH for your plants is important because certain nutrients are only available to plants within a specific pH range.