There are mainly two kinds of causes for the chlorosis of white rice seedlings. The hope is that the majority of farmers will find out the causes of the symptoms and timely treat the symptoms.
One, lack of white
The normal growth and development of rice requires the absorption of 16 nutrients such as nitrogen, phosphorus, potassium and calcium. Each element has its own special function and cannot be replaced with each other. When a certain element is lacking, the growth and development of rice seedlings will be hindered, showing different symptoms. When there are five elements that cannot meet the needs of growth, rice will appear whitish.
1 zinc deficiency. Mostly occurred after the transplanting of rice returned to green, 2 to 3 weeks after the insertion of the tillering period is the peak period of onset. It is often caused by shrinking seedlings not long, the plants dwarf, the leaves of new leaves become shorter and wider, the tillers are less, and the tips of the base leaves are dried first. Then, the middle leaves showed brown to russet irregular lesions, followed by successive lesions from the lower leaves to the upper leaves. The veins were brittle and brittle, the leaf speed was slow, the new leaves became narrow, and the base and midrib areas became green and white. The edges are jagged and the heart is curled.
2 Sulfur deficiency. The growth of rice plants was hindered, the plants were short and the young leaves were yellow, and the veins of the leaves first blew green and then spread throughout the leaves. In severe cases, the old leaves were white, the roots were long, the branches were few, and the white color was delicate.
3 iron deficiency. Generally occurs in the seedling stage of Putian, except that the leaves turn green and turn white, the growth of the seedlings is relatively normal, and no dwarfing or abnormal symptoms appear. The young leaves lose green first, then all the leaves lose green and turn white, but the veins are still green.
4 Boron deficiency. The plants are dwarf, and the tip of the newly emerged leaves turn yellowish-white, curling up, and the apical growth stops when severe. The leaves that grew later were folded and bent, nearly white, but the delivery was more normal than usual, and the newborn delivery could continue to grow. The rice was poorly sturdy, there were many empty shells, and the yield was low.
5 calcium deficiency. When the calcium deficiency was slight, the appearance of the plant was affected little. When the calcium deficiency was severe, the plant was slightly short. The top of the upper leaf became white and curled, and then turned dark brown. The root was short and the apex was brown.
Control measures: Symptomatic fertilization, lack of what supplements and what, and based on the soil pH and the nature and interrelation of various fertilizers, a reasonable application. Improve the permeability of the soil, take measures such as draining water to reduce the groundwater level and re-expanding the soil, and increase the vitality of the root system and its ability to absorb nutrients.
Second, albinism
Yellowing and whitening of seedlings are common diseases of dry rice seedlings and are called yellow (white) disease. Symptoms: The color of the new leaf fades and fades, yellowing, severe albino, not rolling leaf, but the leaf is thin; the old leaf is normal in the early stage of disease, and then gradually turns yellow; the root becomes brown and the absorption function declines. Alkaline soils are prone to this disease, and calcareous sand areas are more prone to occur. In addition, this disease can also occur from applying ash and large-scale application of phosphate fertilizer.
The yellowing and whitening of rice seedlings are caused by the lack of physiological factors in the seedlings and insufficient chlorophyll formation in the leaves. Rice is adapted to absorb reduced nutrients, and it is not easy to absorb and utilize nutrients in certain oxidation states. Under drought-enriched conditions, many mineral elements in the soil such as iron and manganese are oxidized to high valences. These oxidized elements must be complexed with the organic matter in the soil and the organic acids secreted by the roots of rice. Only after the activity is increased can they be absorbed and used by the rice pods. Improper fertilization of seedbeds, poor growth conditions of the seedlings, weakened root oxyntic acid and absorption, and absorption of certain trace elements cannot meet the growth needs of seedlings. Chlorophyll formation in the seedling leaves will be hindered and the seedlings will be yellowed and whitened.
To prevent yellowing and whitening of rice husks, we must first do a good job of soil fertility, apply more fully mature organic fertilizers, use less phosphorus fertilizer, and do not apply plant ash. In areas where the soil is neutral or alkaline, dilute sulphuric acid can be used to adjust the acidity of bed soil. When the pH value of the bed soil is adjusted to 4.5 to 6, it is beneficial to reduce the occurrence of this disease. When seedlings appear yellow and white, spray 0.2% ferrous sulfate has a certain effect, the best effect of foliar spray dry wolfberry green 1st, 24 hours after spraying can be seen on the yellow leaves appear green spots, a few days After the whole leaf turns green, the root system also restores its absorption function.
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