SOIL STRUCTURE

A rich and fertile soil is one which is capturing and retaining as long as possible (or slowing down the passage of) water and nutrient elements through its profile; it is one where all natural nutrient cycling processes are correctly functioning, and in the process releasing optimum amounts of plant nutrients into the soil matrix; and it is one where the rate at which nutrients enter the soil is greater than the rate at which they leave. 

 Conventional agricultural practices have significant adverse impacts on soil structure. These consequences include soil compaction due to heavy machinery, erosion from tilling, loss of organic matter leading to reduced water-holding capacity, disruptions in soil microorganism balance, nutrient imbalances from synthetic fertilizers, soil acidification, decreased soil biodiversity, diminished water-holding capacity, loss of soil aggregation, and long-term degradation. These factors collectively result in soils that are less fertile, less resilient to erosion, and more vulnerable to drought stress and nutrient imbalances. 

BIOLOGY IS THE DRIVING FORCE BEHIND NATURAL SOIL STRUCTURE

The 45% mineral component comes from the gradual weathering of the bedrock. It’s often suggested that an ideal soil ratio consists of 40% sand, 40% silt, and 20% clay. This balanced composition allows the soil to naturally function correctly, enabling optimal water and air infiltration and supporting healthy root growth. Unfortunately these “ideal” proportions are not found everywhere, and agricultural soils inescapably can be excessively sandy or clay-rich.

Within the context of cultivation, soils are typically composed of four essential components: minerals, organic matter from plants and organisms, air, and water. And it is said that an ideal soil structure should have 45% minerals (gravel, sand, silt, and clay), along with 3-5% organic matter. It should also maintain a balance between density and space, with approximately 50% of its volume being empty, equally distributed between air (25%) and water (25%). This balanced soil structure is crucial for fostering healthy plant growth and ensuring proper aeration and water retention in the soil.

However the key to soil performance, which includes efficient water and air movement, ideal nutrient levels, suitable habitat for plants, lies predominantly in its architecture and arrangement, rather than solely by the proportions of gravel, sand, silt, or clay.

Therefore, regardless of the specific quantities of clay or sand in a particular soil, it can be highly productive if it possesses the right organic components. 

Soil devoid of biological activity is essentially geological in nature, conversely, in “living” soils, carbon, along with water, assumes paramount importance as the key components for enhancing soil vitality and productivity.

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