How to prevent and cure rice seedling shrinkage disease

The main causes of rice seedling shrinkage are: phosphorus deficiency, zinc deficiency and saline-alkali injury.

1. Shrinking seedlings due to phosphorus deficiency

It generally occurs in the powder-tillering stage after slow seedling, such as slow growth, short plant, slender and erect leaf shape, dark green leaf color, neat top of leaf cluster, significant shortening of leaf occipital distance, pink tiller, reddish leaf tip and even death of old leaves. The main reasons are: (1) lack of available phosphorus in soil; (2) low soil temperature, low water temperature, or reducing harmful substances such as hydrogen sulfide and ferrous in soil, which reduce the absorptive capacity of roots; (3) excessive application of nitrogen fertilizer, the relative balance of available nutrients is lost.

The control measure is to determine the reasonable amount of phosphorus application according to the data of effective components of phosphorus measured by "soil testing and fertilization method".

Second, shrinking seedlings due to zinc deficiency

Rice has mild zinc deficiency, brown spots on the basal leaves, zinc deficiency in the middle, light green leaves, increased rust, green and white midrib, shortened occipital distance of severe zinc deficiency leaves, growth inhibition, new leaves becoming smaller, plant dwarf, hindrance of powder tillers, serious black root, late heading and serious yield reduction. The main reason is that the content of available zinc in soil is low, or the application of phosphate fertilizer and ammonia fertilizer is too much, and the proportion of ammonia to zinc is out of proportion. In addition, a large amount of organic fertilizer, coupled with long-term stagnant water, is also easy to cause zinc deficiency. The main control measures are: 667m2 (mu) zinc sulfate 1~1.5kg (kg), or after slow seedling shrinkage, 0.1% 0.2% zinc sulfate aqueous solution is applied.

3. Shrinking seedlings caused by saline-alkali injury

This kind of shrinking seedling is a complication of saline-alkali, phosphorus deficiency and zinc deficiency, and most of them occur in coastal rice area. the main performance is that the leaves curl vertically from top to bottom, the roots die quickly, and the leaves do not spit water. The tip of the lower leaves begins to fade from the leaf base after longitudinal curl, and develops upward, and the straight leaves die. The main reasons are the high saline-alkali content of soil or irrigation water, or the high pH value of irrigation water. Main control measures: soaking and alkali washing should be carried out in saline-alkali soil rice areas, and the standard of saline-alkali content in irrigation water should be strictly grasped according to the saline-alkali tolerance of rice at different growth stages, so as to achieve the smooth flow of irrigation water and keep the difference between the water level of the field and the drainage ditch above 40cm, so as to reduce the pH value of the paddy field.