The Chemical Control of Direct Seedlings of Upland Rice
The editors are optimistic about the growing adoption of light-planted dry rice, a method that has increasingly attracted farmers due to its efficiency and profitability. This year, with the government raising the purchase price of rice, the economic returns from dry rice have become more attractive compared to traditional crops like peanuts, corn, and soybeans. However, in regions such as Zhengyang County, where farmers are accustomed to growing these crops, the transition to dry rice has brought new challenges—especially in managing weeds.
Barnyardgrass, a dominant weed species in dry rice fields, is becoming more problematic. Many farmers lack the knowledge of effective weed control techniques, leading to rising costs and frustration. Without proper strategies, weed infestations can severely impact yields, making this an urgent issue for current dry rice production.
One of the main reasons for the rapid spread of barnyardgrass is its diverse genetic makeup, high variability among species, and long seed dormancy, which can last for decades. Once conditions are favorable, these seeds germinate quickly. Additionally, improper herbicide use plays a big role. Some herbicides are not applied at the right time or under unsuitable moisture conditions, reducing their effectiveness. For instance, pre-emergence herbicides work best when soil is moist, while post-emergence treatments need to be applied at specific growth stages. If farmers apply dicloquinal, they must avoid standing water, and quinclorac or penoxsulam should be used before any water accumulation occurs.
Another challenge is the development of resistance in barnyardgrass to certain herbicides. Overuse or misuse of chemicals has led to increased drug resistance, making control more difficult. Furthermore, many farmers rely on natural rainfall rather than controlled irrigation, which can result in poor herbicide performance if the field isn't kept consistently moist after application.
To manage weeds effectively, farmers typically use a three-step approach: pre-planting (sealing), early post-emergence (killing), and mid-season (making up). For example, 30% pretilachlor EC with a safener can be applied 2–3 days after sowing, or 40% propyl benzyl at 60–70 g per mu. Post-emergence treatments like 2.5% Penoxsulam or 35% dichlorobenzyl WP are also effective during the early growth stages of weeds. Farmers should ensure the field remains moist after application and maintain a shallow water layer for several days to maximize herbicide efficacy.
If broad-leaved or sedge weeds are present, combining herbicides like Benazepine with others can help control multiple weed types. In the later stages of rice growth, 25% Benzonsone mixed with 20% dimethyl tetrachloride can be sprayed to target persistent weeds.
In conclusion, controlling weeds in dry rice fields requires a scientific and proactive approach. Farmers should focus on early prevention, choose the right herbicides, follow dosage instructions, and apply them at the optimal time. Combining pre-emergence and post-emergence treatments, along with proper water management, is essential for achieving the best results. With careful planning and execution, farmers can successfully manage weeds and improve the productivity of their dry rice fields.
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