Effect Of Giyphosate On Weed Communities Of Transgenic Soybean Field In The High Latitude And Cold Region

Glyphosate-tolerant soybean line NZL-06-698containing CP4-EPSPS gene was grown in thefield to analyze the effects of glyphosate application years, weeding methods and inter-tillagepractices on weed communities. Split plot design was used, in which the inter-tillage with4levelswere designed as main plot, and weeding methods with5levels were designed as split plot. Themain results are summarized as follows:Inter-tillage was effective on weed control since weed occurrence was depressed with theincrease of tillage times under no weeding treatment. The weed control effect of inter-tillage wasdependent on weed species. For redroot amaranth, the occurrence rate was as the following order:inter-tillage once> inter-tillage twice> inter-tillage for3times>no inter-tillage; the effect oncontrol of the cockspur was different with weeding methods. The order of the cockspur occurrencerate was similar with that of redroot amaranth under the soil-surface dressing treatments andpost-emergence herbicide treatments. The order of the cockspur occurrence rate was as thefollowing order: no inter-pillage> inter-tillage once> inter-tillage for3times> inter-tillagetwice.There is no correlation between the effect of weed control and the numbers of inter-tillage underpost-emergence glyphosate application. No rule was found between the effect of weed control andthe numbers of inter-tillage for the control of chenopodium album.Four weeding methods were designed to explore the effect of weed control under differentinter-tillage conditions. The results showed that post-emergence glyphosate application was themost effective method, and was significantly different from other methods. The post-emergenceherbicide application is better than artificial weeding and the soil-surface dressing treatment. Atthe same time, post-emergence glyphosate application combined with no inter-tillage andinter-tillage for3times were suitable to control redroot amaranth and cockspur, respectively. Theeffect of sowthistle herb control had no significant difference between post-emergence glyphosateapplications under different inter-tillage treaments.Redroot amaranth, cockspur and sowthistle herb were the major weeds in the soybean field innext year under different inter-tillage conditions. The density of the weed occurrence decreasedwith the increase of inter-tillage times, of which the trend was particularly significant for redrootamaranth. While no obvious differnce between inter-tillage for once and twice treatments forcockspur, and for sowthistle herb, the occurrence showed no differnce under all of the treatments.So there was correlation between the effect of weed control and weed species although the densityof redroot amaranth and cockspur under “inter-tillage once” conditions were significantly differentfrom that under the other three inter-tillage treatments.Redroot amaranth, cockspur and chenopodium album decreased rapidly in the field whichplanted glyphosate-resistant soybean for2years continuously. Significant difference of theoccurrence rate of redroot amaranth and chenopodium album were found between different years. The density of low-density weeds such as cocklebur, horsetail, common dayflower etc., changedlittle year-to-year. Resistant weeds were not found in soybean field.The effect of post-emergence glyphosate herbicide was better than convention herbicidewhether in continuous cropping soybean field or maize-soybean rotation field especially forredroot amaranth in continuous cropping soybean field. However, there was no significantdifference in maize-soybean rotation field.