Functions of Crop Nutrient Elements and Symptoms of Deficiency

There are about 16 nutrient elements essential for plant growth. Apart from the major elements carbon, oxygen and hydrogen, which come from the air and water, the rest are all supplied by the soil in which the plants grow. They can further be divided into: the major elements nitrogen, phosphorus and potassium; the secondary elements calcium, magnesium, iron and sulfur; and the trace elements copper, boron, manganese, zinc, molybdenum and chlorine. When nitrogen (N) is supplied in sufficient amounts, growth appears especially luxuriant. On the upper part of the pot surface, the overall effect on plant growth is more obvious than on the roots, and it can be seen at a glance. Especially in the early stage of growth, new shoots are thick and sturdy, there are many leaves, the leaves contain more chlorophyll, the leaf color is bright green, and the leaves also live longer; in the later stage it can also increase the protein content in the plant body, because nitrogen is the main component of substances such as proteins, nucleic acids, chlorophyll, vitamins and alkaloids. If nitrogen is deficient during the plant's growth period, growth will stop. Nitrogen deficiency first shows on the old leaves; the nitrogen-containing substances in the old leaves are decomposed into simple substances and transferred to the young tender leaves to be used, causing the old leaves to age prematurely. However, nitrogen fertilizer must also be applied in the right amount; if there is too much, the stems and leaves grow excessively and it is not easy for flowers to form, and root rot is easily caused. Phosphorus (P) mainly participates in the processes of material transformation and energy metabolism in the plant body, and is important as an intermediate product of photosynthesis, respiration and sugar metabolism. Phosphorus can promote the development and formation of reproductive organs, shown in promoting flowering, producing more buds and blooming well, and it can also make the root system well developed and thick and sturdy. If phosphorus is insufficiently supplied, protein synthesis is blocked, cell division slows, and new cells are difficult to form; therefore, the symptoms of phosphorus deficiency are already very obvious in the early stage of new seedlings, with slow growth, short and small plants, and fewer new shoots. Later there are fewer buds and development is slow, the plant's root system ages and turns rusty in color, there are few white roots, and the roots are thin and short. Potassium (K) can make the colloidal solution of protoplasm tend toward a state of strong fluidity, and potassium can also improve the plant's absorption and utilization of nitrogen. Another very prominent nutritional function of potassium is participating in cell osmotic regulation and controlling the opening and closing of stomata. Potassium can make the leaves upright, the flower stalks stand firm, enhance resistance to disease, and promote root growth. With potassium deficiency, the root system is most obviously damaged, becoming short and small and prone to premature aging, and in severe cases rotting. The above "three major elements" have been introduced in order to master fertilization. As for the secondary and trace elements, they are generally not lacking in soil and are not applied separately, so they are not described in detail here. (Jiangcheng, Zhejiang)