A farmer in xindian town of our city called 123 16 in early July, saying that his machine-transplanted rice had yellow leaves and some plants died soon after planting. It is understood that the weather is dry during rice seedling raising this year, and there has been no water planting, which leads to the older seedlings. When planted, the seedlings are 33 days old, 30 cm high, with 5-6 leaves and thin seedlings. /.2qWQH

Mechanical transplanting is generally a high-density seedling, which is transplanted at the stage of 3-4 leaves, and the elasticity of seedling age is small, generally only 2-3 days. If not planted in time, the seedlings will grow too high, the root system will be weak, and the planting injury will be serious; The quality of seedlings will soon become weak, forming stiff seedlings. After transplanting, the living trees are slow and the tillering ability is poor, which is not conducive to high yield. This year, due to drought and waterless planting in Jiangsu, An Wei and many places, the seedlings transplanted by machines are too old. Especially in areas like Huaibei, which are already short of water resources, irrigation water is not guaranteed and seedlings are seriously over-aged under the severe drought this year. wv & ampt R； & ltbr & gt The seedling age planted in the above fields is 33 days, which is ten days longer than the normal seedling age. The seedlings are weak and seriously injured, and the leaves are prone to yellowing and seedling stiffness after planting. For this kind of fields, it is advisable to manage the thin water layer and irrigate the shallow water frequently. The water depth is about 3 cm, and then put it into the water after the water dries naturally 1-2 days. This repetition has promoted the early growth and rapid development of tillers, with strong plants and developed roots. At the same time, a small amount of fertilizer should be supplemented several times, and about 5 kilograms of urea should be applied per mu each time. & lt/b & gt； #! L% J & ltMX & ltbr & gt Reason 2: Toxic substances poison rice roots \ kym} 5g (

Xie Mou, a farmer in Shiji Town, our city, telephoned 123 16 on July 20th, saying that his hand-planted 4 mu of rice had been transplanted for half a month, and the seedlings had only five leaves. Recently, the leaves of seedlings have become yellow and shortened, and the roots are underdeveloped, but there are a few white roots. It is understood that the previous crop of this land is wheat, and the wheat straw is returned to the field in full when harvesting. As soon as you step into the rice field, many bubbles come out and the soil stinks. {( dP

Generally, in paddy fields where wheat straw is returned to the field, a large number of straws rot in 7- 10 days after water application, and it can only rot completely in about 1 month after water application. Straw rot will consume oxygen in the soil, and when there is water in the field, it often leads to hypoxia in the field soil. Under anoxic conditions, straw rot will produce toxic substances such as hydrogen sulfide and organic acids. Hydrogen sulfide has the smell of rotten eggs and has a strong toxic effect on rice roots. The roots of the affected seedlings turn yellow, and in severe cases, the roots turn black and rot, and the leaves turn yellow and die. In recent years, it is forbidden to burn straw in the open air in our province, and all orange stalks have been returned to fields in many fields. c(E & amp； {+E

The water management of rice field with straw returning should adopt dry-wet alternation, and set water layer 1-2 days for drainage and ventilation for 2-3 days, which can increase the oxygen content of soil and prevent toxic substances from poisoning rice. The weather is dry this year and water is in short supply. Some fields have kept the water layer since transplanting rice, and have not been exposed to water. This will lead to the decomposition of straw under anaerobic conditions, produce harmful substances such as hydrogen sulfide and poison rice roots, and seedlings will appear yellow leaves and shorten. p & gt& ampS7M/9

The above damaged areas should be drained and exposed immediately. Considering that the root system of rice is damaged and the absorption function is reduced, in order to promote the recovery of rice as soon as possible, it is best to spray growth regulators such as sodium nitrophenolate as soon as possible after drainage, and add 0.2%-0.3% potassium dihydrogen phosphate and 1% urea for mixed spraying. In the future, for the field with slow population recovery, compound fertilizer should be applied appropriately to promote tillering, and the field should be postponed appropriately and released lightly several times. Early application of fertilizer at jointing and booting stage can promote tillering into panicles, ensure sufficient panicles and reduce yield loss. 4]IKh，jT

Reason 3: herbicide residues in wheat fields hurt a farmer in Malingshan town of our city by calling 123 16 on July 5, saying that more than 60 mu of local direct-seeded rice was in the heart stage of 4 leaves 1, and the leaves of seedlings in the whole field were yellow and short. It is understood that in the past, 20 grams of 20% sulfometuron-methyl wettable powder was used per mu in wheat fields before winter. Chlorsulfuron and metsulfuron-methyl are sulfonylurea herbicides, which are suitable for controlling weeds in wheat fields. These two drugs remain in soil for a long time, which is harmful to sensitive crops in the following crops. At present, it is only used in wheat fields with neutral or acidic soil in the rice-wheat rotation area of the Yangtze River Basin. Years ago, our province banned the use of long-lasting herbicides such as chlorsulfuron and metsulfuron in wheat fields. hm6pxFkX_

It is understood that after the use of chlorsulfuron and metsulfuron for many years, the drugs accumulate in the soil, which will cause hidden harm to rice. After the application of chlorsulfuron and metsulfuron-methyl in wheat fields before winter, rice can only be transplanted in large seedlings after wheat harvest, such as transplanting small seedlings, throwing seedlings, raising seedlings and direct seeding rice, which is prone to stiff seedlings, delayed seedlings or dead seedlings. The results showed that applying low dose of chlorsulfuron (half of the normal dose) in the heart stage of 1 2-leaf rice seedlings, or applying normal dose within 5 days after transplanting, or in the case of a large amount of drug residues in the field, will cause obvious phytotoxicity to rice production, which is manifested as the growth of roots and buds is blocked, the heart leaves cannot be pulled out, the growing points are deformed or necrotic, the leaves are dark green or lose their green, and the internodes are shortened. It is understood that the 20% metsulfuron-methyl and chlorsulfuron-methyl wettable powder applied in the above fields contains 5% metsulfuron-methyl and 65,438+05% chlorsulfuron, which is registered for spraying annual weeds before winter wheat stands. The recommended dosage of pure medicine per hectare is 65,438+065,438+0.25-65,438+05g, which is about 0% metsulfuron-methyl per mu. The dosage of 20g per mu of the above-mentioned fields is equivalent to 1 g of pure metsulfuron-methyl and 3g of pure chlorsulfuron-methyl. If the dosage is too large, it will easily cause serious phytotoxicity to the next direct seeding rice, and the seedlings will turn yellow and stiff. r*]uR /Z$

Spraying growth regulators such as brassinolide and humic acid foliar fertilizer on rice fields with long-term residual herbicides of chlorsulfuron and metsulfuron is beneficial to alleviate the symptoms of phytotoxicity. Spraying fertilizers such as potassium dihydrogen phosphate and urea can supplement nutrition, enhance the stress resistance of plants and be beneficial to the growth of damaged plants. The previous crops in the above fields use a large amount of chlorsulfuron and metsulfuron-methyl, and even if the above measures are taken, rice may not be able to return to normal growth. Next year, it is best to transplant rice with big seedlings and apply more organic fertilizer to reduce the residues of chlorsulfuron and metsulfuron-methyl in the soil. VRB ~ 7 \ A5 & lt； )

Reason 4: Rice is harmed by saline-alkali RJLFj.

On July 1 1, a farmer in Tangdian Town of our city called the Information Center of Agriculture Bureau and said: Hundreds of acres of local direct-seeded rice are in the four-leaf stage. The leaves of seedlings became yellow, and the rate of diseased plants in the field reached 60%. It is understood that these oil fields have high salt content. Due to drought and water shortage, there is no water layer in the field, and the saline-alkali harm is serious. It was found that after the rice leaves turned yellow, 5-7.5 kilograms of urea was applied per mu after the rain to promote the growth of seedlings. ^9s"FdB]24

The harm of saline-alkali to rice can be divided into direct harm and indirect harm. The direct harm is mainly that the increase of soil salt concentration affects the absorption of water and fertilizer by rice roots, resulting in abnormal physiological activities and poor growth and development of rice plants. When the soil salt content is too high, it will also cause water extravasation, leading to plasma-wall separation, protoplasm destruction and rice seedling death. With the increase of soil salt concentration, the water absorption capacity of rice roots decreases, and the contents of water and chlorophyll in rice stems and leaves decrease correspondingly, while the amount of absorbed and accumulated ions (such as chloride ions) gradually increases, which will directly poison rice, not only harm protoplasm, but also resist the absorption of some mineral nutrients by rice roots, affecting the normal metabolism of nitrogen and sugar in rice plants. Indirect harm is mainly manifested in the destruction of soil structure. Due to the hydration of sodium ions, a large number of sodium ions invade the soil colloid complex, resulting in poor ventilation and water permeability of the soil, poor physical properties, muddy when wet, and hardening when dry, leading to poor root development of rice, enhancing soil reducibility, reducing sulfate in the soil under the action of microorganisms to produce toxic substances such as hydrogen sulfide, endangering rice roots and causing black roots. ? l & gte75V%w

In many places this year, direct seeding of field drought in the early stage of rice growth will accelerate the return of soil salt. This is because when the evaporation of soil water is greater than the precipitation, the surface soil is dried due to the continuous loss of water, and the groundwater will reach the surface soil through the rising movement of capillary and water. While constantly replenishing the water lost by evaporation, the salinity will rise with the capillary water and accumulate on the surface. %pqL-G

Rice has a strong tolerance to saline-alkali, so it is best to irrigate and wash the salt as soon as possible and establish a water layer to pressurize the salt. Spraying foliar fertilizer that can promote growth can reduce the harm of salt to rice seedlings to some extent. Me, J. *CTG

Reason 5: variety resistance mgxz 1d

A farmer in Yaowan Town of our city called 123 16, reflecting that 10 mu of japonica rice, which was directly broadcast by his family, wilted to varying degrees and died, and was diagnosed as rice base rot in the municipal plant protection station, accompanied by black-streaked dwarf disease. @| P3

At present, among the varieties that farmers are used to planting, some varieties are weak in stress resistance, poor in disease resistance, slow in onset and prone to diseases at seedling stage. Here, we suggest that farmers should choose disease-resistant varieties recommended by agricultural authorities when purchasing planting varieties, and don't go into the misunderstanding of seeking cheap or upstart seeds. & lt/b & gt；