Reproduction and offspring competitiveness of Senna obtusifolia are influenced by nutrient availability.

• Senna obtusifolia (sicklepod) is a troublesome weed in many agronomic cropping systems in the southeastern USA with varying fertility regimes. This series of experiments was initiated to determine the impact of nutrient availability on reproductive output and maternal effects. • Experiments were conducted with plants growing in soil in growth chambers for 120 d. Offspring growth was evaluated in hydroponics. • Plants grown under higher nutrient conditions had greater reproductive biomass, number of seeds and total seed biomass. Individual seed mass distributions were slightly affected, with negative skewness decreased at higher nutrition. Seed germination rates were influenced primarily by seed size, as small seeds germinated faster than large seeds. The nitrogen content of seeds increased with increasing seed size and was higher in the high nutrition treatment. Seedlings arising from maternal plants grown under high nutrition grew more rapidly than did seedlings arising from maternal plants grown in a low nutrient regime. • The results suggest that S. obtusifolia reproduction and offspring competitiveness can be strongly influenced by the fertilization regimes used in different agronomic crops and rotations.