In recent years, the occurrence of bitter pox disease in jujube trees has become more and more serious. Juvenile farmers are difficult to control their harm using many conventional methods. The author after analysis that the disease caused by the non-pathogenic bacteria, but due to lack of calcium caused by the date.
First, the symptoms and incidence of jujube bitter pox disease
Jujube ripening, maturing and storage can all exhibit bitter pit disease. When the jujube fruit surface is light green or pale yellow, bitter pox disease is a thick green lesion. As the fruit gradually turns red, the lesions are The color gradually changed from dark green to dark reddish-brown, and spots grew from small to large, forming a dry spot with a diameter of 2-5 mm and a depth of about 5 mm. The dehydration of the pulp at the lesion was brownish sponge and bitter. The site of bitter pit disease is mainly fruit, and the skin of the diseased part appears round or irregular spots centered on the lenticels, usually one or more spots. Lesions often occur near the top of the fruit near the ankle. The onset of the negative on the fruit surface is heavier than on the positive side. In addition, the upper leaves of the jujube tree also appear yellow and the leaves are chlorogenic, dehydrated, and curled. Roots die and form stubby, multi-branched root colonies.
Second, the cause of jujube bitter pit
Judging from the jujube tree, the main nutrient elements in the leaves of the jujube tree were 1.902% calcium, 1.475% nitrogen, 0.928% potassium, 0.589% magnesium, 0.117% phosphorus, 626 mg/kg iron, and 41 mg zinc. Kg, boron 112 mg/kg, copper 7 mg/kg. The order of nitrogen, phosphorus, potassium, calcium, iron and zinc content in fruit development period was nitrogen> phosphorus> potassium> calcium> iron> zinc. It can be seen that the jujube tree is a tree species with a large demand for calcium. Studies have shown that calcium is the most difficult element to flow in various nutrients, and it is not easy to carry out secondary distribution, mostly in stems and leaves, and in fruit. Calcium is involved in the composition of cell wall in the form of pectin calcium in plants. When calcium deficiency occurs, the cell wall cannot form, the adhesive layer in the cell wall of the fruit becomes soft, the softening of the tissue causes the fruit to become fragile and senescent, and the cell wall is severely disintegrated. Imperfections in the cell membrane can lead to leakage, accelerated oxidation, and browning of pulp tissue. The specific reasons are as follows:
1. Insufficient available calcium in soil.
The effective calcium is the ions in the soil solution and adsorbed by the soil colloids. In general, the effective calcium content in the soil is very small, ranging from tens to hundreds of micrograms per kilogram. Calcium in the soil is mostly calcium carbonate, calcium apatite and other insoluble minerals exist, and soil organic matter content is less than 1%, making calcium carbonate, calcium apatite and other minerals difficult to convert into effective calcium.
2. The absorption of calcium in plants is slow to transport and it is unevenly distributed in various organs.
Calcium is transported in the plant by calcium ions through the xylem and phloem along with water, and the transportation speed is much lower than that of water. Among various nutrients, calcium is the element with the lowest phloem transport activity. This feature makes calcium re-distribution and redistribution in the plant very weak. Even if the old leaves and mature leaves are rich in calcium, it is difficult to transport. Go to the fruit. In addition, the transport of calcium is related to transpiration. The leaves of organs with strong transpiration have more calcium, and the fruits with weak transpiration have less calcium; the transpiration of dates in jujube trees is weaker than the periphery, and less calcium is obtained. The yin of the same date is weaker than the transpiration of the sun, resulting in less calcium. The peak of calcium absorption during the young fruiting period is the same as that of Xindiaowang for a long period of time. Since there are many leaves on the shoot, the transpiration is strong, and the calcium is highly competitive, and most of the calcium that enters the plant is absorbed by the new shoot leaves, resulting in There is very little calcium entering the fruit.
3. Antagonism of calcium and other elements.
There are 17 essential nutrients for crops, and there are promoting and antagonistic effects among nutrients. Too much of certain elements will inhibit the absorption of calcium. For example, excessive nitrogen can inhibit the absorption of calcium on the root. On the other hand, nitrogen can promote the growth of crops, promote the absorption of calcium by shoots and leaves, and lead to calcium deficiency in fruits. Potassium and calcium inhibit each other, and any one of them excessively suppresses the other. Iron, manganese, zinc, sodium, boron and other ions and calcium are mutually inhibited relationship. However, boron and calcium have a mutually reinforcing relationship. When the calcium content in fruit trees increases, the amount of boron needs to increase. Therefore, calcium and boron supplements can increase the absorption rate of the two elements.
4. Agronomic measures influence the absorption of calcium.
The jujube garden population structure, tree structure and the size of the load all affect the jujube tree's absorption of calcium. Such as jujube garden planting density, tree closure, poor ventilation and light transmission conditions, jujube garden bitter disease incidence rate is high; tree load is small, resulting in strong tree vigor, new shoot growth Zaanzai bitter disease incidence The rate is high; the tree load is too large, and the calcium and fruit are competed between the fruit and the fruit, resulting in a decrease in the distribution of calcium in the fruit and also in the occurrence of bitter pit disease. In addition, the soil pH, organic matter content, water content, climate factors (atmospheric temperature, air humidity, light) all affect the absorption of calcium.
Third, prevention and control measures
1. Increase organic fertilizer and balance fertilization.
The basic method of jujube calcium supplementation is to increase organic fertilizer, increase soil organic matter content, improve soil physical and chemical properties, adjust soil pH, and provide a good growth environment for jujube trees. 8-10 year old jujube trees apply 1.5-2 kilograms of superphosphate or calcium magnesium phosphate fertilizer, 2-3 kilograms of organic manure etc. per plant in late autumn or early spring, plus soil conditioner. During the growth of jujube, it is necessary to balance the fertilization, and on the basis of reasonable application of nitrogen, phosphorus, and potassium fertilizers, calcium, boron, magnesium, silicon and other elements shall be added. In particular, attention should be paid to the rational use of nitrogen and potassium fertilizers, especially in the late stage of fruit expansion. Control the use of nitrogen fertilizers.
2. Leaf calcium.
Due to the special nature of calcium transport in plants, it is an important measure to supplement calcium on the basis of basic fertilization in autumn and top dressing in spring and summer. Generally in the jujube tree set fruit from the umbilical one month after the peak period of calcium absorption of the fruit, during this period should be sprayed three times, foliar calcium, boron, can significantly increase the pre-calcium absorption of fruit. About 40 days before harvest, jujube fruit can be sprayed twice with calcium-containing foliar fertilizer, which can improve fruit quality and reduce occurrence of bitter pit disease. General use of fruit and vegetable calcium fertilizer, biological chelate calcium, calcium chloride and other leaf fertilizer, in order to increase the absorption rate of calcium fertilizer spraying foliar fertilizer plus boron fertilizer and brassin 481.
3. Reasonably trim and load, minimize girdling.
Timely and appropriate pruning, removing excess internal litchi, pendulous branches, etc. within the canopy, creating a good ventilation and light conditions for the tree. Change the habit of pruning too much and retracting buds. Reasonable load, the head of the fruit does not require too much, for the winter date to ensure each hanging 1-2 fruit. Jujube tree opening and girdling are ways to increase fruit setting rate and yield, but excessive girdling and even repeated girdling will cause roots to age and weaken the tree vigor, which will lead to the occurrence of bitter pox disease in jujube trees. For jujube trees with vigorous growth, plant growth inhibitors can be sprayed to control tree vigor. Strengthen the management of fertilizers and water in the middle and later stages of the jujube garden, and pay attention to the water content of the orchard soil in the late growth period of the fruit, so that the drought can be poured and the water can be discharged. The top-dressing should be controlled by nitrogen, phosphorus, potassium and spray fertilizer in water-soluble fertilizer, stop the root fertilizer application 30 days before picking.
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