The Study Of The Weed Community And Chemical Control In Wheat Fields In Taian

This paper deals with the species of the weeds in wheat fields and their community structure, occurrence principles, distribution patters, sampling techniques and economic thresholds in Taian, and on the basis of the above-mentioned content the selection and mixture application of herbicides were studied.1. The species, damage characteristics and community structure of weeds in wheat fields in Taian.The species of wheat weeds of five areas, Feicheng City, Xintai City, Daiyue District, Ningyang County and Dongping County were investigated by visual five rating method. The results showed that those weeds belonged to 52 species, 18 families, among which, the broad-leaved ones were dominant and were together with some gramineous weeds in some wheat fields. Among broad-leaved weeds, shepherdspurse, flixweed tansymumstard, creepingth-ymeleaf sandwort, conical silene, corn gromwell, wormseed mumstard, tender catchweed, aquatic malachium, and pedunculate trigonotis were dominant, and among gramineous weeds, equal alopecurus, wild oat, and goat grass were in large number.Weeds in wheat fields were mainly biannual, there were three peaks in a year, the first and the biggest one was in the last ten days of October in Autumn, with about 80% of seedling rate of the weeds; the second one was in the middle ten days of March, with about 5% of seedling rate of the weeds,just a small peak; The third one, also a small peak, was in the middle ten days of May, with about 10% of seedling rate. The biannual weeds, as the main control targets, did much damage to wheat, and the annual weeds emerged mainly in Spring, did little damage to wheat.The main weed patterns are shepherdspurse-flixweed tansymumstard-creepingthymeleaf sandwort, flixweed cansymumstard-shepherdspurse-wormseed mumstard, flixweed cansymumstard-shepherdspurse-corn gromwell, shepherdspurse-flixweed cansymumstard-tender catchweed, shepherdspurse -flixweed tansymumstard-equal alopecurus, shepherdspurse-flixweed tansymumstard-aquatic malachium, tender catchweed-shepherdspurse-flixweed cansymumstard, fhepherdspurse-tender catchweed-wild oat- flixweed tansymumstard, flixweed tansymumstard-equal alopecurus-ivy glorybind-common cephalanoplos and so on.2. The effect of herbicides on weed communities in wheat fields in Taian. The single herbicide variety 72% 2,4-D EC, 75% thifensulfurdn-methylDF or 6.9% fenoxaprop-p-ethyl, often used in wheat fields, had been selected for weeds control for 3 years .72% 2,4-D butylate had reduced shepherdspurse , flixweed tansymumstard , but , tender catchweed and equal alopecurus had increased. 75% thifensulfuron-methyl had reduced the number of shepherdspurse, flixweed tansymumstard ,conical silene, but the number of tender catchweed and equal alopecurus had increased. 6.9% fenoxaprop-p-ethyl had reduced the number equal alopecurus, but shepherdspurse , flixweed tansymumstard , tender catchweed and conical silene had increased.3. Research on the spatial distribution pattern and sampling techniques of the main weeds in wheat fields in Taian.The results showed that the spatial distribution patterns of flixweed tansymumstard shepherdspurse, and creepingthymeleaf sandwort belonged to aggregation distribution. The "Z-shaped" sampling were most suitable for both flixweed tansymumstard and creepingthymeleaf sandwort, and bilateraldiagonal sampling were most suitable for shepherdspurse. If all the three weeds were existed, the "Z-shaped" sampling was the best method. When the spatial distribution patterns of the weeds and sampling errors were established, the sampling number was determined by density of the weeds in fields. The sampling number was more when the weed density was lower, and accordingly the sampling number was less when the weed density was higher. When investigating in fields, 20 investigating dots for both flixweed tansymumstard, creepingthymeleaf sandwort and shepherdspurse, and the area of each investigating dot was 0.25 square meters.4. Research on the economic thresholds of the main wheat field weeds in Taian.The relationship expressions between densities(X) of flixweed tansymumstard, shepherdspurse and creepingthymeleaf sandwort and wheat yield injury rates(Y) were Y--50.2267+27.53341nX, Y=-45.9829+24.25451nX, Y=-3 9.0025+20.19251nX respectively, and their ecological economic threshold dynamic models were respectively as follows:y (10000C+100EF+50.2267PVE)/27.5334PVE v_n0000C+100EF+45.9829P\E)/24.2545PVEa—ev_ n0000C+100EF+39.0025PYE)/20.1925PVEa—eIn producing condition, the economic thresholds of 75% thifensulfuron-methyl DF controlling flixweed tansymumstard, shepherdspurse and creepingthymeleaf sandwort were 6.4 plants/m2, 7.0 plants/m2 and 7.5 plants/m2 respectively.5. Research on the chemical control techniques of the main weeds in Taian.Considering status quo that the occurrence density of routine weeds shepherdspurse and flixweed tansymumstard declined and the occurrence density of tender catchweed, aquatic malachium etc. rapidly rised and the occurrence areas of gramineous weeds equal alopecurus, wild oat etc. quickly enlarged, we introduced some new herbicide varieties used in wheat fields,such as 28% thifensulfuron-methyl ? carfentrazone-ethyl WP, 40% carfentrazone-ethyl DF, 3% fluroxypyr, mesosulfuron etc., and the control effect tests of all the herbicide varieties were carried out as well as the chemical control techniques in wheat fields were established.5.1 In the wheat fields which were dominated by flixweed tansymumstard and shepherdspurse, 75% thifensulfuron-methyl DF (lg/666.7m2) or 28% thifensulfuron-methyl ? carfentrazone-ethyl WP (5g/666.7m2) could be used to control the weeds.5.2 In the wheat fields which were dominant by tender catchweed and aquatic malachium, 40% carfentrazone-ethyl DF(4g/666.7m2) or 28% thifensulfuron-methyl icarfentrazone-ethyl(5g/666.7m ) could be used to control the weeds.5.3 In the wheat fields which were dominated by equal alopecurus, 3% esosulfuron(30ml/667m2) could be used to control the weeds.5.4 In the wheat fields which were ? dominated by shepherdspurse, flixweed tansymumstard and equal alopecurus,75% thifensulfuron-methyl (lg/666.7m2) or the mixture of 28% thifensulfuron-methyl ? carfentrazone-ethyl WP(5g/666.7m2) and 3% mesosulfuron(30ml/666.7m2) could be used.5.5 In the wheat fields which were dominated by tender catchweed , aquatic malachium and equal alopecurus, 40% carfentrazone-ethyl DF (4g/666.7m2) or the mixture of 28% thifensulfuron-methyl ? carfentrazone-ethyl WP(5g/666.7m2) and 3% carfentrazone-ethyl OF(30ml/666.7 nf ) could be used to control the weeds.