Intensive cultivation in organic peanut is partially effective, but in-row weed control remains problematic. In an attempt to improve in-row weed control, irrigated trials were conducted from 2011 to 2013 near Ty Ty, GA to determine the feasibility of early-season cultivation perpendicular to row direction using a tine weeder when integrated with other weed-control practices. Combinations of perpendicular cultivation (cultivation perpendicular to row direction), parallel cultivation (cultivation in the same direction of the rows), and banded applications of herbicides derived from natural sources were compared. Perpendicular cultivation improved overall weed control and peanut yield (two years of three), but this benefit was independent of weed control from any form of parallel cultivation. Additionally, tractor tire tracks from perpendicular cultivation across the rows repeatedly crushed peanut seedlings. Parallel cultivation with the tine weeder was generally more effective than parallel cultivation with sweeps, particularly for southern crabgrass and Texas millet. Herbicides derived from natural products were inconsistent in controlling dicot weeds, ineffective in controlling annual grasses, and did not protect peanut yield from weed interference.

Cultivation is a proven means of weed control in organic peanut. However, weeds present in-row often escape control. Research trials were conducted in Ty Ty, GA to modify cultural practices to help suppress weed emergence in-row. Modified cultural practices were three row pattern/seeding rate combinations; twin rows (four rows on a seedbed) seeded at the recommended (1X) seeding rate that produced 13 seed m−1 in each row, twin rows seeded at the 2X seeding rate that produced 23 seed m−1 in each row, and wide rows (two rows on seedbed) seeded at the recommended seeding rate that produced 23 seed m−1. Four cultivation regimes were evaluated; cultivation with a tine weeder at weekly intervals for 6 wk, cultivation with a tine weeder at weekly intervals for 8 wk, scouring with a brush hoe at vegetative emergence followed by the tine weeder for 6 wk, and a noncultivated control. There were no interactions between row pattern/seeding rates and cultivation regimes for any parameter measured. There was inconsistent response of weed control and peanut yield to row pattern/seeding rates. Weed control and peanut yields were similar with tine weeding for 6 wk, 8 wk, or with the brush hoe followed by the tine weeder. Weed management in organic peanut was not improved by altering peanut cultural practices that facilitate quicker canopy closure, and the use of narrow row patterns should not be based on attempts to improve weed control in organic peanut. Narrow row patterns provide other benefits to organic peanut production and those attributes should influence decisions on the choice of row pattern, not weed control.

Field studies were conducted in 2002 and 2003 to determine the effects of herbicides applied below suggested use rates on weed management, yield, and estimated net return of peanut in both narrow and wide row-spacing regimes. In the single row-spacing regime study, diclosulam at 6 g/ha (1/4×) (1/4 labeled use rate) plus flumioxazin at 26 g/ha (1/4×) applied PRE followed by (fb) imazapic POST at 17, (1/4×), 35, (1/2×), or 70, (1×) g/ha was the lowest herbicide input that provided at least 80% control of sicklepod, yellow nutsedge, Florida beggarweed, and hairy indigo at 21 d after treatment (DAT). By 42 DAT, weed control was ≥ 80%, similar to herbicide treatments applied at labeled rates. In the twin row-spacing regime study at Jay, FL, and Citra, FL, in 2003, yellow nutsedge control was lowest (83 to 85%) from diclosulam applied at 1/4× in combination with flumioxazin at 1/4× PRE and flumioxazin at 1/4× or 52 g/ha (1/2×) PRE alone. All other herbicide treatments provided > 90% control. Diclosulam at 13 g/ha (1/2×) fb imazapic at 1/2× and flumioxazin at 1/4× fb imazapic at 1/2× was the lowest rate combination that provided > 80% control of sicklepod. Florida beggarweed control was > 90% with all rate combinations except diclosulam PRE alone, diclosulam at 1/4× PRE fb imazapic at 1/4× POST, and imazapic at 1/4× alone POST. Net return in the single-row spacing regime was highest for flumioxazin at 105 g/ha (1×) PRE alone, diclosulam at 1/4× applied with flumioxazin at 1/4× PRE alone or fb imazapic at 1× ($1,114, $1,094, and $990/ha, respectively). The twin row-spacing regime net return was highest with diclosulam PRE alone at 1/4, 1/2, or 26 g/ha (1×) ($2,063, $1,846, $1,734/ha, respectively). Diclosulam applied with flumioxazin at 1/2× fb imazapic at 1/2× was the lowest herbicide tank-mix input providing high net return at $1,162/ha.