Abstract
A three year field experiment was conducted to evaluate the role of soil inversion, cover crops and spring tillage methods for Palmer amaranth between-row (BR) and within-row (WR) management in glufosinate-resistant cotton. Main plots were two soil inversion treatments: fall inversion tillage (IT) and non-inversion tillage (NIT). Subplots were three cover treatments: crimson clover, cereal rye or none (i.e., winter fallow); and the sub subplots were four secondary spring tillage methods: disking followed by (fb) cultivator (DCU), disking fb chisel plow (DCH), disking fb disking (DD) and no tillage (NT). Averaged over years and soil inversion, the crimson clover produced maximum cover biomass (4390 kg ha−1) fb cereal rye (3698 kg ha−1) and winter fallow (777 kg ha−1). Two weeks after planting (WAP) and before the postemergence (POST) application, Palmer amaranth WR and BR density were two- and four-times less, respectively, in IT than NIT. Further, Palmer amaranth WR and BR density were reduced two-fold following crimson clover and cereal rye than following winter fallow at 2 WAP. Without IT, early season Palmer amaranth densities were 40% less following DCU, DCH and DD, when compared with IT. Following IT, no spring tillage method improved Palmer amaranth control. The timely application of glufosinate + S-metolachlor POST tank mixture greatly improved Palmer amaranth control in both IT and NIT systems. The highest cotton yields were obtained with DD following cereal rye (2251 kg ha−1), DD following crimson clover (2213 kg ha−1) and DD following winter fallow (2153 kg ha−1). On average, IT cotton yields (2133 kg ha−1) were 21% higher than NIT (1766 kg ha−1). Therefore, from an integrated weed management standpoint, an occasional fall IT could greatly reduce Palmer amaranth emergence on farms highly infested with glyphosate-resistant Palmer amaranth. In addition, a cereal rye or crimson clover cover crop can effectively reduce early season Palmer amaranth emergence in both IT and NIT systems. For effective and season-long control of Palmer amaranth, one or more POST applications of glufosinate + residual herbicide as tank mixture may be needed in a glufosinate-based cotton production system.
Highlights
At 2 weeks after planting (WAP), the main effects of soil inversion, cover crop and spring tillage method were highly significant for both BR and WR density (p < 0.0001)
Our research evaluated soil inversion, cover crops and spring tillage methods as an integrated approach to managing Palmer amaranth in glufosinate-resistant cotton production
inversion tillage (IT) alone may result in about 60% reduction in early season Palmer amaranth density
Summary
Compared to other pigweed species, such as common waterhemp [Amaranthus rudis (L.) Sauer], redroot pigweed (Amaranthus retroflexus L.) and tumble pigweed (Amaranthus albus L.), Palmer amaranth produced the highest dry weight, leaf area and height [1]. Palmer amaranth grows relatively quickly and can attain a height of 2 m or more [1]. It is a dioecious plant with tremendous seed production potential and rapid seed germination [1,2,3]. Palmer amaranth can grow under low light conditions, such as dense crop canopies [8]. Palmer amaranth interference and subsequent yield losses have been documented in several crops, such as cotton, corn, cucurbits, grain sorghum, peanut, potato, soybean, sweet potato and several vegetable crops [9,10,11,12,13,14,15,16,17,18,19,20,21,22,23]
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