In recent years, weedy rice has developed into an important threat to rice production in the Yangtze River region, especially in dry-land rice fields. Its harm is like malignant weeds. It grows in the field and cultivated rice. The growth potential often exceeds that of cultivated rice. It competes with cultivated rice for natural resources such as light, water and fertilizer, so that the number of spikes per plant, the number of grains per panicle, and the fruiting Both the rate and the 1000-grain weight were significantly reduced, and the quality of the rice was seriously affected.
It has been observed that the morphological characteristics of weedy rice are different from those of cultivated rice. The weedy rice leaves are broad and green, and the plants are generally high. They are often divided into two types: high and short. The dwarf plant type is more common, the plant type is loose, the tiller angle is large, the leaf sheath is soft and tender, and the dwarf plant type is higher. The type is compact; the root system is obviously developed than the cultivated rice, and the roots are often indefinite; the rice panicle type is large and curved, the number of grains per ear is large, the grain arrangement is sparse, there is awn, the seed setting rate is low, and the husk is golden yellow or brown; In the late growth stage, the stalks and leaves are rapidly senescent and easy to lick the ground; the grains are fine and long, the thousand-grain weight is low, and the surface of the rice grains is reddish brown and brittle.
Weedy rice has both the characteristics of cultivated rice and the characteristics of wild rice, so it can grow naturally in rice fields. First, the leaves are quick to shoot at the seedling stage. Under the conditions of sowing with cultivated japonica rice, weedy rice showed early emergence, early emergence and early tillering. It has been observed that the leaves of weedy rice seedlings are generally 1 to 3 more than the cultivated japonica rice. Second, it is strong. The performance is fast, and there are many tillers. Generally, the number of tillers per plant is 2 to 3 more than that of cultivated rice. Third, the heading period is early. Generally, it is 5 to 7 days earlier than the cultivated rice, and the filling is fast, and the functional leaves are senescent soon. Fourth, it is strong in falling. Weedy rice tends to be granulated when mature, so that a large number of seeds fall into the field before harvesting, which provides conditions for natural reproduction. Seeds without granulation can also be harvested normally with cultivated rice, and mixed in cultivated rice in the coming year. Seeding and emergence, the emergence rate can reach more than 90%. Fifth, the seed dormancy period can be up to 10 years, and the seed that has been dormant will sprout out as long as the temperature is appropriate. Sixth is strong reproduction. According to the data, when there are 1 plant, 3 plants, 5 plants, 7 plants and 9 plants per square meter of cultivated rice fields, the yield can be reduced. The yield reduction ranges are 1.37%, 24.7%, 36.9%, 44.6%, respectively. .
Weedy rice and cultivated rice belong to the same family of Gramineae, and there is no selective herbicide to control it. Through years of research, the author found that agricultural measures can be used to prevent and control.
(1) Implementing water and drought rotation. According to the investigation, water and drought rotation can effectively reduce the damage of weedy rice. There are more than 30 farmers in Wuzhan Town, Tongzhou District, Nantong City. It has been using water and drought rotation for many years (the first year of planting dry land and the second year of planting soybeans). This rotation has been nearly 10 years, and the germination rate of weedy rice can be lowered. It is less than 0.01 plants per square meter, which is much lower than the field of rice that has been planted in a dry year.
(2) Improve farming methods. On the basis of reasonable rotation, the no-tillage field should be rounded every other year or every 2 to 3 years (10-15 cm depth), which can improve the physical and chemical properties of the soil and deepen the weedy rice seeds. Under the soil, the germination rate is greatly reduced.
(3) Improve the rice cultivation method. Although dry-running rice is easy to operate, it is beneficial to the occurrence of weedy rice. Artificial cultivation methods such as artificial throwing, dry breeding, and transplanting, because of the need to plough the land before planting, weedy rice usually occurs less. Therefore, it is recommended to reduce the planting area of ​​dry-broad rice, especially for continuous direct seeding rice, expand the area of ​​hand-planted rice, especially machine-planted rice, and create conditions for water and drought rotation.
(4) Manually remove the impurities. In areas where labor is abundant and the density of weedy rice in the field is not too high, manual extraction can be used to remove weedy rice. The key to manual removal is to master two points: First, the seedling stage is removed, and the weedy rice in the seedling stage is easy to identify. The plant height, stem diameter, leaf width and growth are obviously different from those of cultivated rice. Before (avoid the seeds fall into the field), remove the whole plant early and bring out the field treatment.
(5) Close supervision during the whole growth period. The first is to shut down the good seeds. Strengthen the monitoring of seed breeding fields, screen before planting (cultivation of japonica rice seeds and weedy rice seeds easily), and prevent weed rice seeds from being mixed into the field. The second is to make good education. The selection of the nursery base should check the planting files of the former crops, and ban the farms that are dry-field rice before the ban, and avoid soil-borne seeds. The third is to make a good pass. For the scorpion that has been rotated, it is also necessary to do manual or chemical control to prevent weeding rice seeds from being left behind. The fourth is to close the harvest. Machine harvesting is done to check the work of the machine to avoid weeding rice seeds when harvesting in different places.
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(Source: Jiangsu Agricultural Science and Technology News)
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