Competition for Nitrogen Between Thorn Apple and Tomato and Pepper

Abstract

ABSTRACT The effect of emergence time of the weed Datura stramonium (thorn apple) on tomato (Lycopersicon esculentum Mill.) and pepper (Capsicum annuum L.) was evaluated in a greenhouse experiment. The closer emergence of the weed was to that of the crops, the greater was the weed's growth, seed production, and nitrogen (N) uptake. As a result, growth, fruit yield, and N uptake of the crops was reduced. Shoot N content was reduced in tomato, as was fruit N content in pepper. There was competition by the weed with the crops for N, even when weed emergence was as late as the beginning of flowering. This competition, and the damage it caused, was always more severe with respect to pepper than tomato, irrespective of weed emergence time. The earlier the emergence of Datura stramonium, the fewer were the number of fruits produced by either crop. Average fresh fruit weight in tomato was also reduced. In pepper, the average fruit weight was reduced only when the weed emerged up to the four-leaf stage of the crop. The drop in pepper fruit yield caused by weed emergence up to the four-leaf stage of the crop could be due to competition for light by the weed, in addition to competition for N. Tomato competed better against the weed than did pepper.