پديد آورندگان :
سردار، محبوبه نويسنده دانشكده كشاورزي دانشگاه بيرجند , , بهداني، محمدعلي نويسنده دانشكده كشاورزي دانشگاه بيرجند , , اسلامي، سيدوحيد نويسنده دانشكده كشاورزي دانشگاه بيرجند , , محمودي، سهراب نويسنده دانشكده كشاورزي دانشگاه بيرجند ,
چكيده لاتين :
Introduction
Cotton shows its best growth where no weeds are present in the field and would give an acceptable yield and quality under these conditions. Soil cultivation is a part of cropping operations which is done to prepare the soil suitable for crop planting and consumes about 60% of the mechanical energy used in mechanized agriculture (Jacobs & Harrel, 1983). Herbicides are important tools of weed management in developed countries and they are one of the main pillars for IWM (Vencill & Banks, 1994). These chemicals, however, are most effective where weeds density has been reduced using other methods such as soil disturbances (Musavi, 2009). Trifloxysulfuron- sodium (Envoke) has been introduced as a low dose and is an effective tool in reducing chemical pesticides usage (Burke & Wilcut, 2004). It has been recommended to apply this herbicide at 2-8 leaf stage of cotton growth. The best result, however, has been achieved at 5-8 leaf stage (Richardson et al., 2007). Envoke is recommended at different dosages. The recommended dose in Iran is 15-20 g.ha-1 Envoke WG 75% plus Citogate.
Material and methods
To evaluate the effect of combined dose of different soil tillage methods and weed control on density and diversity of cotton weeds, a split-plot experiment based on randomized complete block design was conducted at the city of Boshruyeh during the rowing season of 2012. Experiment factors were tillage method as the main plot with three levels including conventional tillage, no- till and minimum tillage, and different methods of weed control as sub plots at five levels including the herbicide trifloxysulfuron sodium) Envoke granular formulation with 75% water content of 11.25 g.ha-1+ Citogate %2) at 10, 15 and 20 g.ha-1, as well as a non-weeding and a hand hoeing plot with four replications. Identification of dominant weeds and their density calculations were conducted at three stages including before spraying as well as 15 and 30 days after spraying. Samplings were carried out at these three stages using the data from two 50x50 cm quadrates fixed in each plot between two adjacent ridges. Cotton yield was measured through sampling 20 cotton plants (2.5 m2) from the two central lines after omitting 0.5 m from each side of the planting line as the margin effect. Analysis of variance was done using SAS v8 and comparison of the means was conducted using FLAD at 5% level.
Results and discussion
In this experiment, field weeds included broad-and narrow-leaved weed species including Chenopodium album, Alhaji alhaji, Amaranthus spp., Cynodon dactylon, Sophora secundiflora, Setaria spp., Echinochloa crus-gali, Acroptilon repens L. The results showed that weeds density and composition were considerably affected by tillage methods. The no- and minimum tillage systems increased narrow leaf weeds density by 22.72 and 14.47% compared with conventional tillage, respectively, while these systems decreased the broad leaf weeds density by 65.47 and 48.21%, respectively. Perennial weeds especially Cynodon dactylon were dominant species under the no tillage treatment, but annual weeds like Setaria spp., Echinochloa crus-gali, Amaranthus spp. and Chenopodium album were more dominant under conventional tillage. Both annual and perennial weeds were observed under reduced tillage treatments (chisel and disk). The greatest weed density reduction (narrow and broad- leaved) was observed where 20 g.ha-1 of Envoke with Citogate was sprayed under conventional tillage and conservation tillage was next in the rank. The greatest cotton yield was observed under minimum tillage and hand weeding treatments.
References
Burke, I.C., and Wilcut, J.W. 2004. Weedmanagement in cotton with CGA 362622, Fluometuron, and pyrithiobac. Weed Technology 18: 268-276.
Jacobs, C.O., and Harrel, W.R. 1983. Agricultural power and machinery. Mc Grow Hill Book Companies. New York.
Musavi, M. 2009. The Principlesand Methods of Weed Control. Marzdanesh Publications, Tehran. Iran. (In Persian)
Richardson, R.J., Wilson, H.P., and Hines, T.E. 2007. Pre emergence herbicides followed By Trifluxysulfuron poste mergence in cotton. Weed Technology 21: 1-6.
Vencill, W.K., and Banks, P.A. 1994. Effects of tillage systems and weed management on weed population in grain sorghum. Weed Science 42: 541-547.
