*5.2.5 Plant density and row spacing*

Manipulation of crop row spacing and planting density can restrict weed seed germination and enhance the crop competitive ability against weeds [71]. Narrow row spacing and high plant densities are important techniques in enhancing cucumber competitiveness and suppressing weed growth [16, 72, 73]. These techniques are very cost-effective and environmental friendly. When the optimum plant population density is used through appropriate row spacing, cucumber crop is able to develop canopy cover and hence competitive advantage over emerging weed seedlings [73]. Narrow row spacing is known to suppress weed growth by closing crop canopy earlier than wide spacing. Early canopy cover by closely spaced cucumber has been shown to smother weeds, hence reducing weed-crop competition [16, 74]. Cucumber planted at narrow plant spacing of 1 m × 0.3 m resulted in earlier canopy closure and better weed suppression than those planted at 1 m × 0.6 m and 1 m × 0.9 m [73]. In another study, spacing of 75 cm × 25 cm resulted in weed density and biomass suppression compared to spacing of 75 cm × 50 cm and 75 cm × 75 cm in cucumber [73]. Herbicides work well with narrow spacing as it impacts the weeds by decreasing their vigor due to high competition with the cucumber plants in narrow row planting compared to the wide row planting [73, 74].
