Row spacing is more important than seeding rate for increasing Rhodes grass (Chloris gayana) control and grain yield in soybean (Glycine max)

Abstract

In Australia, soybean (Glycine max (L.) Merr.) is planted at a low density in wide rows, and weeds substantially reduce yield because of opportunities for their growth in the wide rows. Field studies were conducted over 2 years at the University of Queensland farm, Gatton, Australia, to assess the effect of row spacing and seeding rate on the competitiveness of soybeans with a model weed, Rhodes grass (Chloris gayana Kunth). The experiment was conducted in a split-split plot design, replicated three times. Main plots comprised two seeding rates (40 and 80 kg ha–1), subplots two row spacings (25 and 75 cm), and sub-subplots four Rhodes grass infestation periods (weedy from planting to maturity, weedy from 3 weeks after planting (WAP) to maturity, weedy from 6 WAP to maturity, and weed-free from planting to maturity). The results showed that seed rate did not influence Rhodes grass biomass or soybean yield. Soybean yield was greater and Rhodes grass biomass was less in the 25-cm rows than the 75-cm rows. For the 25-cm rows, Rhodes grass biomass in the plots infested beyond 3 WAP was 81–89% less than in the season-long weedy plots, whereas for the wider row crop, this reduction was only 60–75%. For the 25-cm rows, soybean yield in the plots infested with Rhodes grass beyond 3 WAP was 30–36% less than under weed-free condition. However, for the 75-cm rows, this reduction was 56–65%. The results suggest that planting soybean in wider rows caused greater reduction in yield and required an earlier weed management program than planting in narrow rows. The study also suggested that narrowing row spacing was more important than increasing seeding rates for improving weed control and soybean grain yield.

Cultural weed management practices shorten the critical weed-free period for soybean grown in the Northern Great Plains

“…This range of GDDs corresponded to between one (Carman 2016) and three (Carman 2017) soybean developmental stages at both AYL levels. Studies in other regions have found similar results (Hock et al 2006;Nice et al 2001;Rasool et al 2017), as wide-row spacing extends the period of light penetration into the canopy (Puricelli et al 2003;Steckel and Sprague 2004). In this experiment, the canopy did not close completely in the widerow treatments at any of the site-years (data not shown).…”

Junglerice (Echinochloa colona) and feather fingergrass (Chloris virgata) seed production and retention at sorghum maturity

“…However, the extent of competition depends on weed density (Dunan et al 1995), weed type, and weed species (Marshall et al 2003). Weed emergence time (Dieleman et al 1996), growth habit, and duration of the competition (Rasool et al 2017;Swanton et al 2015) influenced the extent of weed-crop competition. Characteristics like tall height (100 to 200 cm tall) and long emergence time of feather fingergrass enable this weed to become competitive, causing substantial seed production (GRDC 2014;Ngo et al 2017).…”

System Intensification in Ridges and Furrow Planting to Enhance Nutrient Uptake Efficiency in Soybean

“…System intensification attempts to increase light penetration through improved crop canopy coverage while minimizing interspecific competition by limiting weed growth [6][7][8]. As a result, soybean planted at closer spacing performs better than crop sown at broader spacing [9,10].…”