The use of NT production practices for jack-o-lantern pumpkin is becoming more widely used in the eastern and midwestern United States (Morse et al., 2001; Rapp et al., 2004; Walters et al., 2008) although most are still produced using conventional tillage (CT). Pumpkin growers have an interest in NT production practices for many different reasons besides just decreasing the overall cost of production. NT practices provide an effective, cost-efficient means of reducing soil erosion, increasing soil organic matter, as well as improving water conservation and nutrient-holding capacities of soils (Blevins et al., 1983; Johnson and Hoyt, 1999). Furthermore, pumpkin fruit produced in NT tend to be cleaner with little to no soil on the fruit skin surface, resulting from pumpkins residing on cover crop or other crop residues, and these pumpkins often garner a premium price compared with those fruit grown in CT that often have soil attached to the fruit (Walters et al., 2008).
The wide-scale implementation of NT practices for pumpkin production has been limited primarily due to the lack of available herbicides to control problematic broadleaf weeds (Galloway and Weston, 1996; Rapp et al., 2004; Walters and Young, 2010; Walters et al., 2008). Chemical weed control is essential to obtain the highest possible pumpkin yields in NT production systems, and tank mixtures of various herbicides are generally necessary to maximize weed control (Brown and Masiunas, 2002; Kammler et al., 2008). Although weeds are a major problem in NT pumpkin production systems, there are limited numbers of registered herbicides available for weed control. The majority of herbicides registered for pumpkins are for preemergence applications and provide limited control of broadleaf weeds and nutsedge (Brown and Masiunas, 2002; Grey et al., 2000); since moisture is required for activation of these herbicides, most are ineffective when limited amounts of rainfall occur within 10 d of application. Although several PRE herbicides including clomazone + ethalfluralin, halosulfuron-methyl, and s-metolachlor will provide better weed control in NT compared with many older cucurbit herbicides, the use of effective postemergence herbicides for control of both grass and broadleaf weeds is important to achieve success in NT vegetable production systems. Grass weeds can be effectively controlled in most vegetable crops with POST applications of clethodim or sethoxydim; however, there is a lack of effective herbicides that can be applied POST for broadleaf weed control in vegetable crops. The only POST herbicide labeled for broadleaf weed control that can be applied over-the-top of pumpkin foliage is halosulfuron-methyl. Halosulfuron-methyl can also be applied PRE in pumpkin for control of several different broadleaf weeds.
The use of other chemical weed management practices for NT pumpkins, such as stale seedbed herbicide treatments or POST-directed herbicide applications to row middles with nonselective herbicides before pumpkin plants vining, may provide viable weed control options. Johnson and Mullinix (1998) indicated that stale seedbed weed management is critical to maximize yields of crops that have limited herbicide options. Maynard (2008) indicated that weeds in NT pumpkins were adequately controlled by using the tank-mixed PRE herbicides (clomazone + ethalfluralin) followed by using a POST-directed shielded application of a nonselective, nonresidual herbicide (glyphosate) to row middles before pumpkin plant vining. Considering the lack of weed management options for NT vegetable crops such as pumpkins, these methods of chemical weed control may provide the additional weed control needed to maximize yields in this type of system. There are limited reports on the influence of NT and crop residue mulching practices in pumpkins, particularly when used in combination with chemical weed control (Walters and Young, 2010). Therefore, a study was conducted to evaluate the effectiveness of using registered herbicides at various timings for weed control in NT pumpkin production following winter wheat harvest.
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