Top 16 nutrients that crops need
Plants require 16 essential nutrients to grow. Nutrient deficiency occurs when a plant lacks a sufficient quantity of an essential nutrient required for growth. Without sufficient nutrients, plants will not grow well and show various symptoms to express the deficiency. But, most farmers have trouble identifying nutrient deficiencies. So, how can you tell what nutrient is deficient?
Examine where on the plant the symptoms began. Since some elements are mobile while others are immobile in the plant, the symptoms of the deficiency will be expressed in the base of the plant on the oldest leaves, top of the plant on the youngest growth, or on the whole plant.
Nitrogen is needed to promote rapid fruit and seed development. It also increases leaf size and quality and hastens plant maturity. Nitrogen deficiency is manifested through general chlorosis of the entire plant to a light green followed by yellowing of older leaves proceeding towards younger leaves. Plants become stunted and secondary shoots develop poorly if the initial symptoms are not corrected.
Phosphorus is essential in photosynthesis, protein formation, seed germination, flower stimulation and budding. It also accelerates maturity. Plants lacking phosphorus exhibit purplish or bronze colouration on the underside of older leaves due to the accumulation of anthocyanin. Affected plants develop slowly and are stunted. Plants absorb potassium as an ion, which can be readily leached and lost through run-off from the soil.
Potassium is important in sugar formation for protein synthesis, cell division and root development. It also increases the plant’s resistance to diseases. Deficiency symptoms include; leaf edge chlorosis on new matured leaves followed by interveinal scorching and necrosis from leaf edge to the midrib as deficiency increases. The chlorosis in potassium deficiency is irreversible even if potassium is given to plants.
Magnesium is a structural component of the chlorophyll molecule. Magnesium is needed by plants to promote the function of plant enzymes to produce carbohydrates, sugars and fats and in the regulation of nutrient absorption. Plants lacking magnesium experience slow growth, leaf size is reduced and lower leaves are shed.
Calcium is needed by plants to produce new growing points and root tips. Plants deficient in calcium have the new foliage, buds and roots stunted. Younger leaves curl downwards with browning of leaf edges and tips, also known as tip burn. In some plants, they may also show abnormally green foliage. Roots become short and stubby.
Iron deficiency is similar to magnesium, except that it appears on young leaves and shoots instead of older ones. Iron is needed by plants for the synthesis of chloroplast proteins and various enzymes. Deficiency symptoms include; light green to yellow interveinal chlorosis on newly emerging leaves and young shoots. It is common to see shoots dying from the tip inwards. In severe cases, newly emerged leaves may reduce in size and turn nearly white, with necrotic spots.
Manganese acts as an enzyme activator for nitrogen assimilation. Plants deficient in manganese have new leaves with diffused interveinal chlorosis and poorly defined green areas around the veins. Chlorosis and necrotic spotting are also common symptoms.
Zinc is essential for the activation of plant growth regulators. Deficiency symptom include chlorosis, bronzing or mottling of younger leaves. Interveinal chlorosis of the young leaves followed by reduced shoot growth with short internodes, as well as small and discoloured leaves giving the affected part a rosette appearance.
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