SANF- SOIL CHEMICAL COMPOSITION
Soil is a vital resource for growing food, fiber, and firewood as it contains most of the nutrients required for their growth. It is composed of solid minerals and organic matter, liquids, and gases that occur on the surface. Soil provides habitats for organisms and moisture and nutrients for the basic requirements of plant growth. Soil is the basis of production in agriculture and forestry.
Healthy soil is always the foundation of the food production system.
Plants obtain nutrients from two natural sources of soil. They are
Both are present in the soil. The organic matter includes any plant or animal material that returns to the soil and goes through the decomposition process. In addition to providing nutrients and habitat to organisms that are living in the soil, the soil organic matter also binds the soil particles to form soil aggregates and improves the water holding capacity of the soil.
A healthy and fertile soil comprises of the following factors:
CHEMICAL PROPERTIES OF SOIL
Macro-elements are the most important nutrients for plants. They occur naturally in the soil to some extent and can be supplemented with fertilizers, manure, and compost. The macro-elements are Calcium (Ca), Magnesium (Mg), Potassium (K), Sulphur (S), Phosphate (P), Nitrogen (N), and Sodium (Na).
Micro-elements are nutrients that plants need in small doses. These are Boron (B), Copper (Cu), Manganese (Mn), Cobalt (Co), Silicon (Si), Zinc (Zn), Iron (Fe), and Molybdenum (Mo).
pH controls a wide range of physical, chemical, and biological processes and properties that affect soil fertility and plant growth. Soil pH, which reflects the acidity level in soil, significantly influences the availability of plant nutrients, microbial activity, and even the stability of soil aggregates. Typically, soil pH values from 6 to 7.5 are optimal for plant growth; however, there are certain plant species that can tolerate, or even prefer more acidic or basic conditions. Maintaining a narrow range in soil pH is beneficial to crop growth. Soil organic matter and clay minerals help to buffer soils to maintain a pH range optimal for plant growth. In instances where the pH is outside a desirable range, the soil pH can be altered through amendments such as lime to raise the pH. Ammonium sulphate, iron sulphate, or elemental sulphur can be added to soil to lower pH.
The salt level is the sum of all the mineral salts that are present in the soil. They can originate from the soil itself, fertilizer, organic manure, and in coastal areas from salt marshes or tidal marshes. When the salt levels in the soil are higher than in the cells of the plant roots, the moisture is drawn from the roots and the fine hair roots die off. Over time this hinders the moisture and nutrients absorption by the plant and causes reduced growth or death of the plant. Crops vary in the extent to which they tolerate salt and the salt levels at which they can still provide a good yield. Some crops grow well in salty soils.
Cation Exchange Capacity (CEC) notes the number of cations that can be bound to the soil. These cations are mainly Ca2+, Mg2+, K+, Na+, and to a lesser extent NH4+, Al3+, Fe2+, Mn2+, and H+. Plenty of Calcium (Ca2+) is important for the soil structure. Calcium keeps the clay platelets at a sufficient distance from each other and in doing so, produces an airy structure. If there is a lot of Potassium or Magnesium between the clay platelets, the clay platelets come too close together, making the soil harder to work. The balance between Ca and Mg is therefore important for the right structure of the soil, as it determines the amount of room there is for water and oxygen.
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