Archives

We develop a generalized sigmoidal model and we used it to describe the growth of a local tall landrace of sorghum from Jazan region of Saudi Arabia. This sorghum is grown year-around for fodder and in early fall for grain. The plants were grown in 80-L pots under near-ideal conditions. Heading occurred 62 days after planting (DAP), while physiological maturity was reached after 105 DAP. Evolution of plant growth as a function of time was best represented by the sigmoid model dot y = ky(1 - y/a) where a = 251.11006 is the maximum height that the plant can theoretically reach and k = 0.00234 represents the cultivar's typical growth rate. It appears that this local sorghum landrace is a short-season cultivar given its short life cycle. However, this may vary slightly by location and year since the actual plant growth rate depends on several environmental factors such as soil fertility, ambient temperature, moisture availability, planting density and prevalence of pests.
Key words: Sigmoidal model, Sorghum, Phenological Stages.