The Influences Of Different Herbicides On Weed Control And Rice Growth And Output In Mechanical Direct Seeding Fields

With more and more rural labor transferring to cities, management entities of rice production has been changing. Choosing an optimal rice planting technology aiming at improving production process, reducing operation cost and increasing production efficiency has been a momentous problem for rice production around China. In recent years, rice production in China is of a rising mechanization and mechanical direct seeding has developed rapidly around, but direct seeding rice is still of some problems, like the unstable stand establishment and high-cost weed control, etc. Fyou 498 was selected as trial material to study the weed control effects of different herbicides applied separately or assembly at different growth stages in direct seeding rice fields. In addition, the influences of herbicide residue in soil, direct seeding rice tiller dynamics, the growth and development characteristics of rice group and grain yield were studied simultaneously. The main results were as following:1. Butachlor (C2) spraying at 2d after rice was sowed (T1) integrated with penoxsulam (S4) spraying at 4th leaf stage (T2) could control weeds significantly, while the separate spraying of any kind of herbicides could not control weeds at mid-term stage, especially for malignant weeds like barnyard grass. Different types of herbicides had different weed control effects on different weeds in the same period and the results were as follows:the weed control effect of C2 was better than that of pretilachlor (C1), and less weeds were found in Butachlor spraying treatment, but C2 showed slight disruption on rice growth, cyhalofop-butyl spraying (S3) at T2 controlled barnyard grass, Chinese sprangletop, and crabgrass more effectively than other herbicides, but could not weed cyperus difformis and lindernia procumbens as effectively as the others. Soil treatment agent spraying at T1 integrated with steam-leaf treatment agent spraying at 4th leaf stage could weed out most of weeds. For weed control stage, weeds would be controlled more effectively when herbicides were sprayed at T1 than T2. Butachlor sprayed at 4th leaf stage controlled barnyard grass, Chinese sprangletop, rotala indica and crabgrass more effectively than pretilachlor spraying at the same stage.2. The tillering duration of direct seeding rice with T1 treatment was shorter, its maximum tillering stage was earlier, and its effective panicles was less than other treatments consequently. Be different with the tillering number, T1 treatment showed little influence on root growth at early growth stage and root thrived well. Direct seeding rice with T2 treatment developed too much ineffective tillering, and its effective panicle rate was smaller, but it still maintained the most effective panicles. Herbicides spraying at 4th leaf stage would exert negative influence on root growth at early stage, but its root could grow well at late growth stage and effectively accelerate the dry matter accumulation and transportation. Herbicides spraying elongated tillering duration to some extent, while its nitrogen absorption was slightly less than manual weeding. Butachlor spraying would show a negative effect on root growth at seedling stage, and then direct seeding rice tillering subsequently. However, with the growth process moving forward, the negative influence receded, and root could grow well at late growth stage, so nitrogen absorption and dry matter accumulation and transportation were both in good condition, and effective panicle rate and grain yield increased consequently, penoxsulam and cyhalofop-butyl spraying boosted direct seeding rice tillering and elongated tillering duration. During the whole growth stage, rice root developed well, which effectively promoted dry matter accumulation and transportation and nitrogen absorption in leaves and panicles of direct seeding rice, so the integration of penoxsulam and cyhalofop-butyl could show more distinct advantages.3. Herbicide weeding effected ineffective tiller significantly, and its effective panicles, effective panicle rate and 1000-grain weight of direct seeding rice were all higher than those with manual weeding, while the seeting rate and spikelets number per panicle were of little difference, hence, herbicide weeding rice obtained higher grain yield than manual weeding rice. In addition, herbicide weeding could extirpate out weeds more effectively and prevented their comeback, which would weaken weeds’competitiveness with rice for nutrients, and facilitate dry matter accumulation and transportation. Correlation analysis showed that their were significant positive correlations between grain yield and root dry weight and root-shoot ratio, implying that higher grain yield of herbicide weeding treatments were partly attributed to the auxo-action of herbicide weeding to root growth.4. Compared with manual weeding, herbicide weeding could reduce a cost of 670.5 to 1240.5 yuan per hectare. As for grain yield, herbicide weeding treatments grained as many grains as manual weeding treatments, or even higher grain yield, like T3C1S4 å'Œ T3C2S4. Hence, taking the weed control costs into consideration, T3C1S4å'Œ T3C2S4 obtained much higher profits than manual weeding. Compared with the mixed use of 6 kinds of herbicide, the separate use of any herbicide would leave more residue in soil, while it would not do harm to rice growth. To sum up, compared with manual weeding, herbicide weeding had the advantages of low cost, high efficiency, good effects and less soil residue, hence, herbicide weeding could save a large amount of labor and has the same or even higher economic benefits than manual weeding.