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Saint Joseph, LA, United States

Kumar V.,Montana State University | Kumar V.,Louisiana State University | Udeigwe T.K.,Texas Tech University | Udeigwe T.K.,Louisiana State University | And 4 more authors.
Agricultural Water Management | Year: 2015

Regional variations in environmental conditions, cultivars, and management practices necessitate locally derived tools for crop water use estimation and irrigation scheduling. A study was conducted in northeast Louisiana (mid-south US) aimed at estimating daily crop evapotranspiration (ETc) and reference evapotranspiration (ETo) and thus, developing local crop coefficient (Kc) curves for irrigated upland cotton. ETc was determined using paired weighing lysimeters installed near the middle of a 1-ha cotton field and planted with cotton as in the rest of the surrounding field, while ETo was calculated using the Standardized Reference Evapotranspiration Equation (SREE) developed by the American Society of Civil Engineers (ASCE), using estimates of weather variables from a nearby standard reference weather station. Stage-specific Kc values averaged over 2 years were 0.42, 1.25 and 0.70 for initial, midseason, and end season stages of cotton, respectively. The initial-stage Kc value was approximately 26% lower than the Food and Agricultural Organization (FAO)-adjusted initial Kc value. The mid- and end-season Kc values obtained in the study were approximately 6% and 11% greater, respectively, than the FAO-adjusted Kc values for the corresponding stages. The observed differences among the local stage-specific Kc values (especially at initial growth stage of cotton) and the FAO-adjusted initial Kc values could be attributed to regional variations in environmental conditions, cultivars, and management practices. The ETc and Kc values obtained from this study provide research-based information for future studies and the development of Kc-based irrigation tools in this region. © 2015 Elsevier B.V.


Miller D.K.,nter Northeast Research Station | Downer R.G.,Grand Valley State University | Stephenson D.O.,nter Dean Lee Research Station
Journal of Cotton Science | Year: 2010

Past research has shown that a postemergence (POST) mixture of a residual herbicide, such as Smetolachlor, with glyphosate can result in improved weed control and maximize cotton yield. Published research is limited on the tolerance of a POST mixture of an aqueous capsule suspension (ACS) formulation of pendimethalin with glyphosate applied at different growth stages to cotton. Research of this issue is important as producers continue to search for cost savings in cotton production, and the inclusion of residual herbicides such as pendimethalin in the planting regimen is needed to abate the expansion of glyphosate-resistant (GR) weeds. This research was conducted in 2006 and 2007 to evaluate the effects of POST combinations of glyphosate with an ACS formulation of pendimethalin on second-generation GR cotton growth, development, and yield. Treatments evaluated in the study included a factorial arrangement of herbicides [glyphosate (®Roundup Weathermax) at 1540 g ha-1 alone or in combination with ACS pendimethalin (®Prowl H2O) at 1064 or 2128 g ha-1 or S-metolachlor (Dual Magnum) at 1064 or 2128 g ha-1] and cotton growth stage (4- to 5- or 6- to 8-leaf). Ammonium sulfate at 2524 g ha-1 was included with each treatment. Results indicated that visual crop response in the form of veinal yellowing and slight leaf malformation can be observed following a POST tank-mixture of pendimethalin with glyphosate. Response is limited to contacted leaves. Visual crop response following mixture of glyphosate with pendimethalin was minimal 21 d after both application timings and was not manifested in reductions in plant height or seedcotton yield compared to glyphosate applied alone. © The Cotton Foundation 2010.


Miller D.K.,nter Northeast Research Station | Downer R.G.,Grand Valley State University | Stephenson D.O.,nter Dean Lee Research Station
Journal of Cotton Science | Year: 2010

Research has documented the effects of tankmixing glyphosate with numerous insecticides on cotton growth and yield; however, no information is available concerning the addition of a residual herbicide such as an aqueous capsule suspension (ACS) formulation of pendimethalin to glyphosate plus an insecticide. Mixtures such as this are important as producers continue to search for costs savings in cotton production and the inclusion of residual herbicides in the planting regimen is needed to mitigate the development and spread of glyphosate-resistant (GR) weeds. Therefore, this research during 2006 and 2007 determined the effects of postemergence (POST) combinations of glyphosate applied alone or plus the ACS formulation of pendimethalin with eight different insecticides on second-generation GR cotton. Glyphosate (®Roundup Weathermax) was applied at 1058 g ha2O alone or tank-mixed with pendimethalin (®Prowl H2O) at 1064 g ha2O. The insecticides acephate (®Orthene 90 SP) at 560 g ha2O, betacyfluthrin (®Baythroid XL) at 37 g ha2O, dicrotophos (®Bidrin 8 E) at 448 g ai ha2O, dimethoate (®Dimethoate 4E) at 280 g ha2O, imidacloprid (®Trimax) at 53 g ai/ha2O, lambda-cyhalothrin (®Karate Z) at 37 g ha2O, oxamyl (®Vydate C-LV) at 448 g ha2O, thiamethoxam (®Centric 40 WG) at 53 g ha2O, or zeta-cypermethrin (®Mustang Max) at 25 g ai/ha were also tank-mixed with glyphosate and pendimethalin. Results indicate that visual crop response in the form of minor malformation and veinal yellowing of contacted leaves can be observed following a POST co-application application of pendimethalin with glyphosate (3 to 16%). Addition of insecticides to the glyphosate plus pendimethalin mixture did not affect visual injury. Plant growth and seedcotton yield were not impacted by treatments. © The Cotton Foundation 2010.

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