The environmental physiology of tomato (Lycopersicon esculentum Mill. cv. Heinz-6004) and black or eastern black nightshade (Solanum nigrum L. and Solanum ptycanthum Dun.) competition

The growth of the black and eastern black nightshade was analyzed and predictive models were developed. Black and eastern black nightshade were planted on June 3, June 23, and July 12 in 1988 and May 28, June 17, and July 10 in 1989. All plantings were harvested 20, 40, and 60 days after planting, and dry weights and leaf areas determined. Degree-day models accurately predicted the growth of both species for all planting dates. Eastern black nightshade produced significantly more biomass than black nightshade, although the weight of berries was equivalent for both species. Eastern black nightshade responded to self shading by increasing specific leaf area.Black and eastern black nightshade were established at densities of 0-4.8 per m$\sp2$ in irrigated Heinz 6004 processing tomatoes during the summers of 1989 and 1990. Increasing densities of either nightshade species decreased the number of tomatoes per vine, but eastern black nightshade had the greatest effect on yield (both the number of fruit per vine and the kg of tomatoes per ha). As the season progressed, eastern black nightshade overtopped tomato vines and allowed progressively less photosynthetically active radiation (PAR) to reach the top of the canopy. The PAR reaching the top of the canopy was positively correlated with yield, negatively correlated with eastern black nightshade density, and was unaffected by black nightshade. Black nightshade remained shorter than tomatoes throughout the growing season and did not affect yield. PAR in the middle and at the bottom of mixed nightshade-tomato canopies decreased with increasing densities of either nightshade species. Eastern black nightshade competed intraspecifically while black nightshade did not. Increasing density of black nightshade decreased berry dry weights, but increased the mass of stems and leaves.U of I OnlyETDs are only available to UIUC Users without author permissio