What are the control methods for zinc deficiency stunt seedling in rice?

Phosphorus deficiency stunt seedling generally occurs at the tillering stage after seedling recovery, manifesting as slow growth, short plants, slender and upright leaves, dark green leaf color, neat leaf cluster tips, significantly shortened leaf sheath distance, red tips on some tiller leaves, and brownish-red or even dead old leaves. Causes: first, the soil lacks available phosphorus; second, low soil temperature and water temperature, or the presence of reducing harmful substances such as hydrogen sulfide and ferrous iron in the soil, which reduces the root's absorption capacity; third, excessive application of nitrogen fertilizer, causing the effective nutrients to lose their relative balance. Control measures determine a reasonable phosphorus application rate based on the available phosphorus data measured by the "soil testing and fertilizer recommendation method."

Zinc deficiency stunt seedling: In mild zinc deficiency in rice, brown spots appear on the basal leaves; in moderate zinc deficiency, the leaf color is light green, rust disease increases, and the midrib turns chlorotic and white; in severe zinc deficiency, the leaf sheath distance shortens, growth is inhibited, new leaves become smaller, plants are short, tillering is hindered, black roots are severe, heading is delayed, and yield is severely reduced. Causes: low available zinc content in the soil, or excessive application of phosphate fertilizer and ammonia fertilizer causing an imbalanced ammonia-to-zinc ratio; in addition, heavy application of organic fertilizer combined with long-term waterlogging can also easily cause zinc deficiency. Control measures: apply 1-1.5 kg of zinc sulfate per 667 sq m, or after seedling recovery, when stunt seedling occurs, shallowly topdress with a 0.1%-0.2% zinc sulfate aqueous solution.

Salt-alkali damage stunt seedling: This type of stunt seedling is a complication of salt-alkali damage, phosphorus deficiency, and zinc deficiency, mostly occurring in coastal rice areas. It mainly manifests as leaves rolling longitudinally from top to bottom like green wilt, roots rapidly necrotizing, no guttation from leaves, and lower leaves rolling longitudinally at the tips, then chlorosis starting from the leaf base and developing upward until the leaves die. Causes: high salt-alkali content in the soil or irrigation water, or high pH of the irrigation water. Control measures: In salt-alkali soil rice areas, soak the fields to wash out alkali. During the rice growth period, according to the salt-alkali tolerance of rice at different growth stages, strictly control the salt-alkali standard of irrigation water, ensure smooth irrigation water flow, and maintain a water level difference of more than 40 cm between the field surface and the drainage ditch water level, so as to lower the pH of the rice field.