Seed Production, Germination, Emergence and Growth of Tithonia diversifolia (Hemsl.) A. Gray as Influenced by Different Sowing Depthsand Soil Types

Seed production, germination, emergence and the influence of planting depths and soil types on growth of T. diversifolia were determined from the harvest made in 2013 fruiting season. Natural population of Tithonia diversifolia stands growing on a clay soil was used for the study. Number of capitulum heads per plant was in the range of 35-212 with each capitulum head carrying seeds in the range of 32-62. Depending on the size and number of capitulum heads number of seeds per plant ranged from 1120-13,144 with average of 897,342 seeds per square meter. The seeds were small and light in weight as indicated by 100-seed weight (0.51-0.72 g) with 93% viability. The seedlings that emerged from soil showed greater growth efficiency and vigour compared to seedlings obtained from seeds plated in petri-dishes. The young seedlings emerged at all depths studied with seeds sown on soil surface having 76.76 % germination while those at the depth of 3.5 cm showing 5%. Growth parameters such as root length, shoot length, leaf area, leaf number and dry matter accumulation increased significantly (p≤0.05) with decrease in sowing depth. The plant grew in all types of soils investigated with maximum growth in loamy followed by clayey and sandy soil. The foregoing results could be used to account for the aggressive nature of this plant.