Plant height as a factor in competition between black nightshade and two horticultural crops (tomato and pepper)

SummaryIn a glasshouse experiment the differential competitive relationship between black nightshade, tomato and pepper was investigated at four times of weed emergence. Thus, the weed emerged at the six, four and two-leaf stages of both crops and simultaneously with them. Black nightshade competed for light and nutrients with tomato only when the weed height exceeded that of the crop from the beginning of tomato flowering onward, as it was the simultaneous emergence that reduced tomato fruit yield (36.5%), number of fruits and N, P and K uptake. Competition between the weed and pepper for light and nutrients was more severe, even when weed emergence was delayed until the six-leaf stage of the crop which reduced fruit yield, number of fruits and N, P and K uptake. The earlier the weed emerged relative to the pepper, the less the crop height and yield. Pepper yield was reduced by 29, 44 and 62% when the weed emerged at the six, four and two-leaf stages respectively. Black nightshade that emerged simultaneo...