Weed management in strip-tillage cotton



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The number of strip-tilled cotton acres on the Texas Northern High Plains has increased to compensate for high energy costs as well to conserve water and manage soil erosion. Strip-tillage is a tillage system in which strips (generally 25 to 30 centimeters wide and 76 centimeters from center to center) are tilled prior to planting rather than broadcast tillage. The strips serve as the seedbed. It is likely that the number of strip-tilled cotton acres will continue to increase as producers attempt to reduce inputs to improve profitability for a given crop. In order for a strip-tillage cropping system to be effective, weed control must be achieved. The development of herbicide-resistant cotton varieties has facilitated the shift from conventional-tillage to strip-tillage systems and has also led to the reliance on herbicides as a primary means of weed control. The lack of broadcast tillage presents some unique problems with the use of preplant incorporated (PPI) herbicides (primarily dinitroanilines). In addition to herbicides applied PPI, herbicides are also applied after planting prior to crop emergence (preemergence, PRE), and after crop emergence (postemergence, POST) in order to lessen or eliminate weed competition with the crop.

The objective of this study is to evaluate various weed management systems in strip-tillage cotton using PPI herbicides applied broadcast and incorporated into the tilled strip to control weeds prior to planting, and using PRE and POST herbicide applications following planting. Studies were conducted in Farwell, Texas in 2006 and 2007 on Acuff and Bippus soils under center-pivot irrigation. FiberMax 960BR was planted in 2006 and FiberMax 9058F was planted in 2007. The study was arranged in a randomized complete block design with four replications. Individual plots measured 4.5 by 9 meters. Treatments consisted of all combinations of pendimethalin PPI at 1.12 kilograms active ingredient per hectare (kg ai/ha), trifluralin PPI at 0.84 kg ai/ha, prometryn PRE at 1.34 kg ai/ha, and POST treatments of either glyphosate at 0.84 kg acid equivalent/ha or a tank-mix of pyrithiobac at 0.071 kg ai/ha plus S-metolachlor at 1.42 kg ai/ha. All treatments were applied with either a CO2 backpack sprayer or a tractor-mounted compressed air sprayer, both of which were calibrated to deliver 93.5 L/ha. Visual assessments of Palmer amaranth [Amaranthus palmeri (S.) Watts.] and devil’s-claw [Probiscidea louisianica (Mill) Thuellung] control were made throughout the growing season on a scale from 0 to 100%. Two rows by 2 meters were hand-harvested from each plot at crop maturity. Data were analyzed as a factorial. All standard error of the difference values (SED’s) are from LSmeans statements using the pdiff option in Proc MIXED in SAS. Significant interactions as well as main effects were separated using LSD at the P=0.05 level of significance.



Weeds in cotton, Weed management, Weed, Strip-tillage