Implications of cover crop planting and termination timing on rainfed maize production in semi-arid cropping systems

Field Crops Research · 2021 · 51 citations

• Agronomy
• Environmental science
• Biology

Despite the potential to increase soil organic matter, cycle soil nutrients, and suppress weeds, there is a concern that cover crops (CCs) soil water use negatively impacts subsequent crops in water-limited environments. Cover crop management practices such as planting and termination timing may mitigate the detrimental impacts of CCs in semi-arid cropping systems. To determine the effects of CCs under water-limited environments, we evaluated the total CC biomass produced in the fall and spring, soil water content during the subsequent maize growing season, weed density and biomass, crop residue, and soil nutrients at the maize V6 development stage, and maize productivity. The experiment was conducted under a wheat-maize-fallow rotation at two sites (Grant and North Platte, NE) during 2016−2017 and 2017−2018. Treatments consisted of three planting timings after winter wheat harvest and three CC termination timings and fallow (no CCs) before maize establishment. Planting CCs shortly after winter wheat harvest increased CC biomass in the fall and early spring compared to late planting. Cover crops terminated early in the spring reduced weed biomass (−70 %), while CCs terminated late in the spring reduced both weed density (−56 %) and biomass (−82 %) compared to fallow. Due to above-normal precipitation during the experiment, soil water measured at 0−20 cm soil depth was impacted by CCs only at Grant 2016−2017. Cover crops terminated late in the spring increased crop residue biomass but decreased total nitrogen at 0−10 cm soil depth by 17 %, and decreased soil nitrate at the 10−20 cm soil depth up to 26 % compared to fallow. Cover crops planted late in the summer (August) and terminated late in the spring (May) had the most detrimental impact on maize grain yield. Late termination of CCs in the spring reduced corn grain yield by up to 20 % compared to fallow. Despite enhanced weed suppression and crop residue, CCs decreased soil nitrogen and maize grain yield, especially when terminated late in the spring. Producers in semi-arid regions of the Great Plains willing to incorporate CCs should use caution when selecting management strategies for their CCs to minimize maize grain yield and economic losses.

Seed-shattering phenology at soybean harvest of economically important weeds in multiple regions of the United States. Part 1: Broadleaf species

Weed Science · 2020 · 33 citations

• Biology
• Agronomy

Abstract Potential effectiveness of harvest weed seed control (HWSC) systems depends upon seed shatter of the target weed species at crop maturity, enabling its collection and processing at crop harvest. However, seed retention likely is influenced by agroecological and environmental factors. In 2016 and 2017, we assessed seed-shatter phenology in 13 economically important broadleaf weed species in soybean [ Glycine max (L.) Merr.] from crop physiological maturity to 4 wk after physiological maturity at multiple sites spread across 14 states in the southern, northern, and mid-Atlantic United States. Greater proportions of seeds were retained by weeds in southern latitudes and shatter rate increased at northern latitudes. Amaranthus spp. seed shatter was low (0% to 2%), whereas shatter varied widely in common ragweed ( Ambrosia artemisiifolia L.) (2% to 90%) over the weeks following soybean physiological maturity. Overall, the broadleaf species studied shattered less than 10% of their seeds by soybean harvest. Our results suggest that some of the broadleaf species with greater seed retention rates in the weeks following soybean physiological maturity may be good candidates for HWSC.