Question

Name two plant macronutrients that are bound to clay in their ionic forms

Answer 1

Macronutrients are essential for plant growth and a good overall state of the plant.

The primary macronutrients are Nitrogen (N), Phosphorus (P), and Potassium (K).

Nitrogen
Nitrogen fixation is also a biological process. Some species of bacteria, algae actionmycetes can absorb free nitrogen gas N2 and convert it to ammonium NH4+ which plants can use. Some nitrogen fixing bacteria are free livings, such as Azotobacter and require carbohydrates in their substrate. Others are symbiotic, such as Rhizobia, that infect root mainly of legumes. The infected roots eventually from nodules in which the free nitrogen is fixed from them it is translocated to other parts of the plant. However the account of nitrogen fixation is reduced when nitrogen is applied as fertilizer. Other microorganisms known to free nitrogen as blue green algae, which flourish in rice, paddy. Among anaerobic bacteria one should mention clostridium.

Phosphorus

Phosphorus is the second most important plant nutrient next to N for plant growth and development. Retention refers to that portion of the P which is loosely held by the soil and which can generally be extracted with dilute acids.

- Forms of organic phosphorous

• Phospholipids
• ucleic acids.
• Inositol phosphates

- Inorganic soil phosphorus

• Orthophosphate ions- H2Po4 and HPO4

Potassium

Potassium is the major nutrient, which imparts increased vigour and disease resistance to plants and improves the quality of final products. Relative proportions of the total soil potassium in available, slowly available and readily available forms only 1-2% is rated as readily available of this 90% is exchangeable and only 10% appears in the soil solution at any time.