The basic components of soil are minerals, organic matter, water and air. The typical soil consists of approximately 45% mineral, 5% organic matter, 20-30% water, and 20-30% air. These percentages are only generalizations at best.

clay

Loamy soil

The B horizon is commonly referred to as “subsoil” and consists of mineral layers which are significantly altered by pedogenesis, mostly with the formation of iron oxides and clay minerals.

This, however, can lead to environmental problems, soil loss, and degradation. Soil degradation is a human-induced or natural process which impairs the capacity of soil to function. Other activities that degrade the soil include contamination, desertification, and erosion.

restricting root growth because of high soil strength and low aeration. increasing erosion which lessens the long term productivity of the soil. restricting seedling emergence if the surface crust dries out. Overcultivation with implements, such as the disc plough, is a major cause of soil structure decline.

Compost. Adding compost to a sandy or clay soil significantly improves the soil structure, which in turn makes plants healthier. Compost is the great equalizer; a 2-inch layer of compost incorporated into the top 6 to 8 inches of soil will help clay soil become more porous and sandy soils less porous.

Climate and topography influence soil structure through factors such as temperature, precipitation, elevation, slope gradient and directional aspect. Soil properties such as texture, mineralogy, SOC and organisms interact and moderate the influence of the climate.

A good soil structure is important to allow air and water into the soil which are vital for healthy plant growth. It will improve drainage and reduce soil erosion caused by excess surface run-off. Without structure, soils will suffer from anaerobism, waterlogging and nutrient lock-up and, ultimately, plants will die!

Soil structure not only affects the ability of roots to grow and to supply the leaves with water and nutrients; if adverse, it also induces them to send hormonal signals that slow the growth of the shoot, even if they are currently able to take up adequate water and nutrients.

Some of the soil properties affecting plant growth include: soil texture (coarse of fine), aggregate size, porosity, aeration (permeability), and water holding capacity. An important function of soil is to store and supply nutrients to plants. Greater clay and OM content will generally lead to greater soil fertility.

There are three main types of soil: sand, silt, and clay. The best soil for most plants to ensure optimum growth is a rich, sandy loam.

The physical properties of the soil are very important for agricultural production and the sustainable use of soil. The amount and rate of water, oxygen, and nutrient absorption by plants depend on the ability of the roots to absorb the soil solution as well as the ability of the soil to supply it to the roots.