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Rice seedlings lack of fertilizer symptoms and remedy
The availability of essential nutrients in rice fertilizers typically includes nitrogen (N), phosphorus (P), potassium (K), and zinc (Zn). Each of these nutrients plays a vital role in the growth and development of rice plants, and their deficiency can lead to distinct visual symptoms. By observing these symptoms, farmers can perform a nutritional diagnosis and take appropriate corrective measures to improve plant health and yield.
Nitrogen deficiency in rice seedlings often begins with yellowing at the tips of older leaves, which gradually spreads throughout the plant. The lower leaves turn yellow, while the upper leaves remain green for a while. The leaves become narrow, short, and upright, and the plant appears stunted. Tillering is reduced, and root development is delayed. This condition is commonly found in fields with poor base fertilizer application, such as those with yellow mud or "slim feet" soil. To address this, it's important to apply nitrogen-rich fertilizers like ammonium bicarbonate (25 kg per acre) or urea (10 kg per acre), mixed into 20 buckets of clear pig manure and applied to the field.
Phosphorus-deficient rice seedlings may fail to green up after transplanting or show slow growth after emergence. Leaves become thin, and in severe cases, they curl along the veins. The leaf color turns dark green, sometimes with a blue-violet tinge at the tip. The plants are weak, with short, thin roots and few new roots. To correct this, farmers should apply a mixture of superphosphate (30 jin) and ammonium bicarbonate (30 jin) per acre, combined with shallow water irrigation. This helps increase surface temperature, enhancing phosphate absorption and metabolic activity in the roots.
Potassium-deficient seedlings exhibit yellowing with brown spots on the leaves, especially at the tips. As new leaves emerge, the lesions on older leaves worsen, and only a few new leaves remain green. The main and branch roots are short, thin, and discolored, with no new root growth. This deficiency is common in cold, waterlogged, or rust-affected paddy fields. Immediate drainage is crucial, followed by the application of 150 kg of wood ash per acre, preferably in the morning when dew is present. Alternatively, foliar spraying of potassium dihydrogen phosphate (2 kg per mu in 60 kg of water) can be effective. Combining this with nitrogen fertilizer and practicing shallow water drying can improve root health and nutrient uptake.
Zinc deficiency in rice seedlings initially shows as chlorosis, whitening, or red spots on the middle portion of the lower leaves. These areas expand into reddish-brown stripes, eventually leading to dryness from the leaf tips. The disease progresses upward, causing slower leaf growth, shorter and narrower new leaves, and chlorotic discoloration near the base of the midrib. Roots also turn brown. To treat this, farmers should drain the field, allow sunlight to reach the soil, and promote root regeneration. Foliar sprays of 0.2% zinc sulfate solution, applied once a week for two weeks, can help restore plant health.