It is imperative for a farmer to know and understand how the plants utilize nutrients provided for their growth, how these nutrients are used and taken up from the soil where they reside before absorption to the plant system.
This will enable the farmer to detect any obstruction or foul play in the plant system. Also, it will show whether the plants are truly utilizing the nutrients provided within the soils or it’s just a waste. It will also show whether the fertilizer applied is genuine, that is really efficient, or not. The knowledge of how the plants take up nutrients from the soil is really cogent and must be known to all farmers, as you read along you will get to know this.
Plants absorb nutrients from the soil mostly in the forms of ions. Plants need sixteen (16) essential elements or nutrients for good growth and yield, they are:
• Carbon.
• Hydrogen.
• Oxygen.
• Phosphorus.
• Potassium.
• Nitrogen.
• Sulphur.
• Calcium.
• Iron.
• Manganese.
• Magnesium.
• Boron.
• Copper.
• Zinc.
• Molybdenum.
• Chloride.
In the above listed nutrients, some of them are called mobile nutrients while some are called immobile nutrients.
The immobile nutrients are the types that are slowly translocated through the plant to the region where that are most needed. These nutrients are; Calcium, Iron, Manganese, Boron and Chloride. They accumulate in the lower regions of the plants such as roots and older leaves, consequently starving the young plants when these nutrients are in short supply in the soil. Their deficiency symptoms are usually more observed in the younger and upper parts of the plants.
The mobile or fast moving nutrients are Nitrogen, Potassium, Phosphorus, Magnesium, Sulphur, Zinc and Molybdenum. They accumulate more in the younger and upper parts of the plants. Their deficiency symptoms are first observed in the lower parts of the plants.
Plants may obtain nutrients by absorption through either the leaves or the roots. Carbondioxide for example enters the plant almost entirely through the stomata, which are the small openings into the interiors of the leaves. Water is also absorbed through the stomata but the amount is small in comparison to the amount of water entering through the roots. Nutrients are supplied by the following processes.
1. Mass flow.
2. Diffusion.
3. Root interception.
Mass flow
Mass flow is the movement of plant nutrients through the soil in the moving water mass. Large amounts of water are transpired by plants, most of this water is first absorbed by the plant roots, then move through the roots and stems and finally lost through the stomata of leaves.
The continuous absorption and transpiration of water by plants means that large volume of water must move through the soil. The water with the dissolved nutrients also called soil solution moves through the soil to the plant roots. There, the water and the dissolved nutrients are absorbed into the plant cells.
Diffusion
This is the movement of nutrients from the medium of higher concentration to that of lower concentration.
When plant roots absorb nutrients from the soil solution, other dissolved nutrients move from higher concentration zones to areas of lower concentration of such nutrients to ensure it is fully utilized.
Root interception
This is the absorption of nutrients by the root extensions. As plant roots grow, they ramify into new areas of the soil where they meet or intercept ions that are there in solution. This root extension decreases the distance needed for plant nutrients to move by mass flow or diffusion in order to arrive at the plant root surface.
Many nutrients, when sprayed, are capable of being absorbed by leaves of plants but plants absorb most nutrients through their roots.