| Information sheets | | | Elsenburg infopaks | | | Soil: 2 |
Fertiliser
Afrikaans | Xhosa
References exist to writings on soil fertility and plant feeding, that are older than 4 500 years, and to writings in which the value of different kinds of animal manure as plant nutrients (the food of plants) is classified, that are older than 2 500 years.
All plant-growth material consists of water and a flammable part that leaves ash after combustion. These ingredients are taken up from the soil by plant roots. Continued removal without any replacement gradually impoverishes the soil so that food, fibre and feed production decreases.
All plant food taken up from the soil, is taken up in dissolved form by water. The plant roots, take up this plant food (also called plant nutrients) from large areas below the soil surface, in small quantities, to concentrate it in the above-ground growth.
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Animals, in turn, eat these plants in larger quantities than they need, so that the excess is excreted in the animals’
manure. When the manure is placed back into the ground, this often causes markedly improved plant growth.
As agricultural science progressed, man succeeded in analysing the ingredients of animal manure and plant residue. This developed in the successful production of fertilisers with high concentrations of plant nutrients |
Fertiliser ingredients can be divided into two groups. The ingredients of one group are required in large quantities for plant growth and are called macro-plant-nutrients. The ingredients of the other group are required in much smaller quantities and are called microelements.
The following are the most important ingredients of each group:
| Macro-elements | Micro-elements | ||
| N | Nitrogen | Cu | Copper |
| P | Phosphorus | Zn | Zinc |
| K | Potassium | Mn | Manganese |
| S | Sulphur | B | Boron |
| Ca | Calsium | Fe | Iron |
| Mg | Magnesium | Mo | Molybdenum |
All these elements, in different quantities, are essential for normal plant growth. Each also has a different role in plant nutrition. However, I am going to refer only to the three most important plant-nutrition elements or kinds of plant food, namely nitrogen, phosphorus and potassium, or N, P and K.
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Why are these three plant nutrients so important?
N - Nitrogen Found in the flammable part of dry plant material. If plants take up enough N, rapid leaf growth and leaves with a healthy green colour are promoted. A nitrogen deficiency causes leaves to have a light yellow-green colour. This is more apparent on older leaves. In such cases the plants remain dwarfed and produce lower yields. Plants that take up enough N produce high yields of a good quality. Two of the most important sources of N for plants, are rotted plant residue such as manure or compost, and N-containing fertilisers. The two most important forms of N, namely nitrate or ammonium, are freely soluble in water, and can therefore be washed out of the soil by too much rain or irrigation water. Therefore always make sure that there is enough N in the soil for the plants to take up. N-containing fertilisers can be used for this purpose. In order for plants to grow quickly, some N must be worked into the soil even before sowing or planting. |
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P - Phosphorus
An ingredient of plant ash. Most soils in South Africa are poor in phosphorus and do not contain enough to sustain normal plant growth. P is essential for the growth of all plants, but smaller quantities are needed than of N. P is essential for the division of cells at the growth points of the plant roots underground, as well as at the growth points of plants above the ground. If the plants take up too little P, they grow slowly and remain small, and the ripening of especially grain seeds is slowed down. Because P is important for cell division, much of it is stored in seeds, from which new growth develops. Fertilisation with P or sufficient P in the soil for plant nutrition is therefore necessary for rapid and strong root growth so that plants can utilise the other nutrients and water in the soil. This makes plants more resistant to droughts and plant diseases. Too much P in the soil or too much of it added by way of fertiliser, is not really harmful for plant growth, but it is a waste of money. P deficiencies occur in ruminants grazing on P-deficient pastures. The animals become emaciated, cows calve irregularly, young animals show poor growth, and animals develop adhesions on their hoofs and walk with great difficulty. The massive withdrawal of P from the frame can be observed in the bones. Deviating appetite results in the chewing of strange objects such as tins, pipes, stones and bones. |
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K - Potassium
An ingredient of plant ash. Potassium does not constitute an important part of plant tissue, but it does play an important part in the plant sap in the plant cells, in that it aids the plant in producing certain other materials that are important for growth. In maize and other grains, adequate K uptake by the plant strengthens the stem so that it is not easily lodged by strong wind. In vegetables, adequate K gives good quality, keeping ability and size. Plants readily take K up from the soil with water, often in quantities larger than is necessary for normal growth. In all plant species N, P and K are therefore necessary for producing good yields. When harvests and plant material such as pasturage are removed from soils, the plant nutrients are removed. If N, P and K are not replaced in the soil in the form of fertiliser, manure or compost, the soil is gradually impoverished and it will increasingly produce less food for man and beast. Therefore, when we speak of N, P and K, we refer to the plant nutrients and fertilisers that are essential for producing large yields. |
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S - Sulphur |
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Ca - Calcium |
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Mg - Magnesium |
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Cu - Copper |
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Zn - Zinc |
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Mn - Manganese |
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B - Boron |
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Fe - Iron |
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Mo - Molybdenum |
CP de L Beyers
ELSENBURG / Nitrophoska
