Growth Dynamics of Senna obtusifolia (L.) Irwin and Barneby as Affected By Nitrogen Fertilizer in Soils of Contrasting Fertility in the Nigerian Dry Forest Ecology
*R. O. Awodoyin, Sola Ogunyemi and A. O. Togun
Department of Crop Protection and Environmental Biology, University of Ibadan, Ibadan, Nigeria.
*Corresponding author e-mail: frawodoyin@yahoo.com
Accepted in January 2004.
Abstract
The effect of nitrogen fertilizer applied at the rate of 0 (N0), 50 (N1) and 100 (N2) kgN/ha on growth and dry matter accumulation in sicklepod [Senna obtusifolia (L.) Irwin and Barneby] was studied in pot culture in sandy loam soil (S1; pH 3.9) and silty loam soil (S2; pH 7.2) to understand its growth behaviour in soils of contrasting fertility levels. The studies were completely randomized design. The growth parameters were evaluated at 14-day intervals from 28 to 98 days after sowing (DAS). The potting soil, nitrogen fertilizer and harvest period had significant effects (P £ 0.05) on plant height, leaf area, total plant dry weight and leaf dry weight. 犀利士
The soil x harvest period interaction was significant (P £ 0.05) for all growth parameters, while soil x N interaction was significant for only leaf area and leaf dry weight. The leaf weight ratio (LWR) decreased from 0.62 in S1 and S2 plants at 28 DAS to 0.31 in S1 plants and 0.37 in S2 plants at 98 DAS. The relative growth rate (RGR) and dry matter production (DMP) were high and more or less stable up to 70 DAS when they abruptly decreased. LWR, DMP and RGR varied significantly with the harvest period of sicklepod. The soil had significant effect on LWR and DMP but had no significant effect on RGR. Nitrogen fertilizer significantly affected DMP, but not LWR and RGR. For all growth parameters, nitrogen influence on plant was in the order of N2 > N1 > N0 in the marginal (S1) soil. However, in the relatively fertile (S2) soil the order was N2 > N1 > N0 at the early growth stage and N1 > N2 > N0 at the late growth stage. Factor interactions were not significant on LWR, DMP and RGR. The results suggested that sicklepod has rapid growth and yield performance in both marginal and fertile soils, a quality that may adapt it for use as green manure and fallow plant to restore the productivity of exhausted agricultural fields. The rapidity of establishment is also implicated in its competitive and invasive effects.