Study On Occurrence Regularity And Chemical Control Measures Of Weeds In Cotton Fields In Shandong Province

Cotton Is one of the most important economic crops in our country. In general conditions, the plantation area of cotton could be5.3to5.5million hectares. Shandong Province, one of the most desirable areas of cotton, is the traditional and major producing province of cotton in the The Yellow River, which had a long history of cotton cultivation. But, weeds in the cotton field had been a serious problem of efficient production of cotton. In this paper, the species, community composition and occurrence regularity of weeds in cotton fields in Shandong Province had been investigated, analysised and studied. Based on the occurrence regularity of weeds in cotton fields, we took series methods such as bioassay, pot-culture in greenhouse and field expriment to figure out several promising combinations of soil-applied herbicides in cotton fields. The results could be summarized as follows:1. The results of weed survey in cotton fields of Shandong province for two years (2012,2013) showed that68weed species, which belong to24familes and49genera, existed in the cotton fields of Shandong province. Among these species,4,10,17, and37weed species were considered as dominant weeds, regional dominat weeds, common weeds and normal weeds, respectively. The overall abundance of Eleusine indica, Portulaca oleracea, Digitaria sanguinalis, Acalypha australis, Imperata cylindrical and Phragmites australis was relatively higher.2. According to the survey, the main plantation area of cotton of Shandong Province mainly centralized in the following four cotton regions:Jining, Heze, represented for the Southwest cotton region; Liaocheng, Dezhou, represented for the northwestern region; Binzhou represented for LuBei cotton region; Dongying represented for the northeast coastal saline cotton region. Based on the structural characteristics of weed community, cotton regions of Shandong can be divided into two categories. The north and northeast cotton region was one category, the southwest and northwest region was another type.3. According to the occurrence regularity of weeds in cotton fields, there were three peak periods for weeds’ emergence, distributed in the late May, late June or early July and middle August separately, and most of the weeds emerged in the first period. The total amount of the weeds in the natural community reached the peak at the end of June and appeared unimodal change in the whole growing season of cotton.4. The results of bioassay in greenhouse indicated that pendimethalin, acetochlor had higher control efficiency against on common grassy weeds in cotton fields, but had universal validity against on most broadleaf weeds. Flurochloridone, pyrithiobac-soidum grass had excellent control efficiency against on broadleaf weeds, and certain control efficiency against on grassy weeds. So the jointed herbicides of fluorochloridone, yrithiobac-soidum, pendimethalin and acetochlor can broad the spectrum of weed controlling effectively.5. The evalution results of joint effect indicated that the joint effect of fluorochloridone, pyrithiobac-soidum, pendimethalin and acetochlor were additional or beneficiated effect against weed. The detection of selective index showed that the two jointed herbicides of flurochloridone and pendimethalin against on cotton and Digitaria sanguinalis, Amaranthus retroflexus were16.94,16.57separately; the two jointed herbicides of flurochloridone and acetochlor were19.91,20.26separately; the two jointed herbicides of pyrithiobac-soidum and pendimethalin were9.46,15.90separately; the two jointed herbicides of pyrithiobac-soidums and acetochlor were10.66,19.37. This suggests that flurochloridone, pyrithiobac-soidum, pendimethalin, acetochlor and their mixture were safe on cotton.6. The field research showed that the additional and beneficiated effect of jointed herbicides of fluorochloridone and pendimethalin,acetochlor, the jointed herbicides of pyrithiobac-soidum and pendimethalin, acetochlor were outstanding. Especially, the mixtures of fluorochloridone and pendimethalin,acetochlor were better than the mixtures of pyrithiobac-soidum and pendimethalin, acetochlor.