The lodging problem is also one of the limiting factors for high rice yield. Although the lodging problem has been alleviated with the cultivation of dwarf rice varieties. However, in recent years, some high-quality rice plants are over 1m tall, and the planting density is slightly higher, or more nitrogen fertilizer is applied to achieve high yields, which also has the risk of lodging. For example, if there is a strong wind after heading, the plants are more likely to lodging.
With the development of cost-saving and efficient cultivation technology, manual and mechanical seedling throwing has gradually replaced transplanting, but the seedlings are shallowly buried in the soil, and lodging is more likely to occur in the later stage. In recent years, direct-seeded rice and upland rice have developed, but lodging is serious, which limits the improvement of yield and harvesting efficiency.
- Application time
The best effect of applying paclobutrazol at the jointing stage, that is, 30 days before heading, is to control internode elongation, increase internode weight, control plant height, and prevent lodging. If used too early or too late, the effect is not good.
- Application concentration
The higher the concentration of paclobutrazol used in the jointing stage, the more obvious the effect of controlling plant height, but the panicle type also decreases, the total number of grains per panicle decreases, and the number of panicles per unit area also tends to decrease. If the concentration of paclobutrazol reaches 700~800mg/L, the leaves will be deformed, dark green, and severely necked. Therefore, the concentration of paclobutrazol should not exceed 500mg/L. It is appropriate to spray 60kg of 300mg/L paclobutrazol solution per mu, and the effective ingredient amount is about 20g per mu.
- Technical effect
In the leaf age before rice jointing, applying about 20g of paclobutrazol per mu of field can make the internodes thick and short, the center of gravity of the plant is lowered, the bending moment is small, and the bending resistance is improved; the cellulose and lignin content of the base internodes increases, and the degree of lignification of the stem fibers is increased;
The stem wall and mechanical tissue are thickened, the mechanical tissue is developed, the field closure is reduced, the ventilation and light transmittance are increased, and lodging can be effectively prevented.
- Technical evaluation
The application of paclobutrazol to prevent rice leggy growth is effective, but whether it can increase yield depends on whether the control lodging. In the case of no lodging, the use of paclobutrazol will reduce yield.
The reason is that applying paclobutrazol before jointing inhibits internode elongation and also inhibits the development of young spikelets, resulting in small spikelets and fewer grains. Applying it earlier or later (before or after jointing) reduces the effect on the spikelets, but the anti-lodging effect is poor. Therefore, only applying paclobutrazol in fields with excessive growth can prevent lodging and increase yield.
When applying in production, you can use 15% wp diluted 500 times to get a 300 mg/L paclobutrazol solution, and spray the seedlings on the leaves.