Oregano green manure for weed suppression in sustainable cotton and corn fields

Published source details Vasilakoglou I., Dhima K., Anastassopoulos E., Lithourgidis A., Gougoulias N. & Chouliaras N. (2011) Oregano green manure for weed suppression in sustainable cotton and corn fields. Weed Biology and Management, 11, 38-48.
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This study is summarised as evidence for the following.

	Action	Category
	Incorporate plant remains into the soil that produce weed-controlling chemicals Action Link

Incorporate plant remains into the soil that produce weed-controlling chemicals

A randomised, replicated, controlled trial in 2005-2007 in northern Greece (Vasilakoglou et al. 2011) found that incorporating oregano Origanum vulgare into the soil reduced the abundance of three weed species in cotton Gossypium hirsutum and maize Zea mays. In cotton, green manure reduced numbers of the weed common purslane Portulaca oleracea by 30-55% (55-85 vs. 121 plants/m²), barnyard grass Echinochloa crus-galli by 48-52% (23-25 vs. 48) and bristly foxtail Setaria verticillata by 43-86% (1-4 vs. 7). Maize plots with green manure had 0-45% fewer common purslane (71-128 vs. 129), 38-46% fewer barnyard grass (7-8 vs. 13) and 60-80% fewer bristly foxtail (1-2 vs. 5). The cotton yield was significantly lower in green manure treatments than in a weed free control, but not different to (and in once case higher than) an unweeded control. Maize silage and grain yields were similar between treatments. There were four oregano green manure treatments (plants from four locations, selected for high concentrations of potential allelopathic chemicals) and two controls without green manure (one weeded) replicated four times in 9 x 5 m plots. Oregano was incorporated 8-10 cm deep before flowering. Cotton and corn were planted five days later.