Growth Model of Sowthistle (Ixeris dentata Nakai) Using Expolinear Function in a Closed-type Plant Production System

The objective of this study was to make growth and yield models of sowthistle (Ixeris dentata Nakai) by using an expolinear functional equation in a closed-type plant production system. The growth and yield of hydroponically-grown sowthistle were investigated under four different planting distances (15 x 10, 15 x 15, 15 x 20, and 15 x 25 cm). Shoot dry weights per plant was the highest at 15 x 25 cm, but was the lowest at 15 x 10 cm. Shoot dry weights per area was the highest at 15 x 15 cm, but was the lowest at 15 x 25 cm. The optimum planting density and planting distance for yield of sowthistle were 44 plants/m(2) and 15 x 15 cm, respectively. Shoot dry weights per plant and per area were showed as an expolinear type functional equation. A linear relationship between shoot dry and fresh weights was observed to be linear regardless of the planting distance. Crop growth rate, relative growth rate and lost time in an expolinear functional equation showed quadratic function form. Radiation use efficiency of sowthistle was 4.3-6.1 g.MJ(-1). The measured and estimated shoot dry weights showed a good agreement using days after transplanting as input data. It is concluded that the expolinear growth model can be a useful tool for quantifying the growth and yield of sowthistle in a closed-type plant production system.