Cereal rye cover crop and herbicide application method affect cotton stand, Palmer amaranth (Amaranthus palmeri) control, and cotton yield

Abstract

Six on-farm studies determined the effects of a rolled rye cover crop, herbicide program, and planting technique on cotton stand, weed control, and cotton yield in Georgia. Treatments included: (1) rye drilled broadcast with 19-cm row spacing and a broadcast-herbicide program (2) rye drilled with a 25-cm rye-free zone in the cotton row and a broadcast-herbicide program (3) rye drilled with a 25-cm rye-free zone in the cotton row with PPI and PRE herbicides banded in the cotton planting row, and (4) no cover crop (i.e., weedy cover) with broadcast herbicides. At two locations, cotton stand was lowest with rye drilled broadcast; at these sites the rye-free zone maximized stand equal to the no-cover system. At a third location, cover crop systems resulted in greater stand, due to enhanced soil moisture preservation compared with the no-cover system. Treatments did not influence cotton stand at the other three locations and did not differ in the control of weeds other than Palmer amaranth at any location. Treatments controlled Palmer amaranth equally at three locations; however, differences were observed at the three locations having the greatest glyphosate-resistant plant densities. For these locations, when broadcasting herbicides, Palmer amaranth populations were reduced 82% to 86% in the broadcast rye and rye-free zone systems compared with the no-cover system at harvest. The system with banded herbicides was nearly 21 times less effective than the similar system broadcasting herbicides. At these locations, yields in the rye broadcast and rye-free zone systems with broadcast herbicides were increased 9% to 16% compared with systems with no cover or a rye-free zone with PPI and PRE herbicides banded. A rolled rye cover crop can lessen weed emergence and selection pressure while improving weed control and cotton yield, but herbicides should be broadcast in fields heavily infested with glyphosate-resistant Palmer amaranth.

Effects of cereal rye seeding rate on waterhemp (Amaranthus tuberculatus) emergence and soybean growth and yield

“…Cornelius and Bradley (2017) found that out of nine cover crop species or mixes tested, cereal rye was the only fall-seeded cover crop to suppress early-season waterhemp emergence in soybean in Missouri at a comparable level to a PRE residual herbicide program. Hand et al (2019) found that roller crimped cereal rye could suppress early-season Palmer amaranth emergence in cotton (Gossypium hirsutum L.) to similar levels as a thorough broadcast herbicide program in Georgia. More recently, Schramski et al (2020a) found that in Michigan, planting a cash crop directly into nonterminated (green) cereal rye and winter wheat [Triticum aestivum L.] reduced early-season glyphosateresistant horseweed [Conyza canadensis (L.) Cronq.]…”

“…Increased incidences of herbicide-resistant weed species and public concern over reducing anthropogenic inputs in agriculture have generated renewed interests in incorporation of cover crops in the United States row crop production systems (Hand et al 2019;Wittwer 2017). According to the 2017 National Agriculture Census data, cover crops were planted on 6.2 million hectares, with highest adoption occurring in the mid-Atlantic region (Zuluaf and Brown 2019).…”

“…Cereal rye has been shown to effectively suppress early-season weed emergence in cash crops, especially small-seeded broadleaf weeds such as waterhemp and Palmer amaranth, which depend on light for germination (Cornelius and Bradley 2017;Hand et al 2019;Teasdale 1996). Cornelius and Bradley (2017) found that out of nine cover crop species or mixes tested, cereal rye was the only fall-seeded cover crop to suppress early-season waterhemp emergence in soybean in Missouri at a comparable level to a PRE residual herbicide program.…”

“…These seeding rates vary across climate and state (USDA-NRCS 2012, 2018). In the previously-mentioned studies on weed control with cereal rye, Cornelius and Bradley (2017) seeded cereal rye at 123 kg ha −1 ; Hand et al (2019) seeded at 100 kg ha −1 ; and Schramski et al (2020a,b) seeded at 67 kg ha −1 . Approved USDA-NRCS seeding rates for drilled or broadcasting cereal rye in Missouri are 44.8 kg ha −1 and 56.0 kg ha −1 , respectively, whereas rates in Georgia are less specific, ranging from 62 to 126 kg ha −1 (USDA-NRCS 2015).…”

Establishing white clover (Trifolium repens) as a living mulch: weed control and herbicide tolerance

“…Cover crops improve soil stabilization (Hartwig and Ammon 2002;Sanders et al 2018), water infiltration (Hartwig and Ammon 2002), soil water holding capacity (Echtenkamp and Moomaw 1989), soil organic matter (Cherr et al 2006), and soil nitrogen when legumes are used (Andrews et al 2018;Cherr et al 2006;Sanders et al 2017), and lead to the diversification of soil microbial communities (Vukicevich et al 2016). In addition to these soil health benefits, cover crops also reduce weed emergence and growth, providing an additional benefit for managing herbicide-resistant weeds and mitigate further development of resistance (Bunchek et al 2020;Hand et al 2019;Teasdale et al 2007). Although annual cover crops are typically planted, other researchers have proposed intercropping or use of a living mulch (Affeldt et al 2004;Andrews et al 2018;Hiltbrunner et al 2007;Pedersen et al 2009;Sanders et al 2017Sanders et al , 2018.…”