PJB-2019-320
DEVELOPMENT OF A PHENOLOGY PREDICTION TOOL FOR LOCAL SORGHUM FROM SAUDI ARABIA
Fethi Soltani
Abstract
Temperature is a key factor controlling the kinetics of biological processes such as growth and development of plants. The present study was carried out to develop a simple, thermal time-based mathematical model which can be used by growers and field technicians to predict growth and developmental stages of a local economic crop, sorghum (Sorghum bicolor (L.) Moench). The objective of this study was to develop equations to predict grain sorghum canopy structure characteristics (plant height and number of leaves). Data from pot-grown plants were used to develop equations that relate canopy structure parameters of grain sorghum to the total above ground dry weight. Growth data from an open-field of sorghum of the same land race were used to validate those equations. This dynamic model uses ordinary differential equations (ODE) to describe the growth of plants as a function of thermal time expressed as heat units accumulated from the time of seed sowing until harvest to avoid the usual variations in the time duration needed for the plant to complete its life cycle which varies with ambient temperature fluctuations. Heat unit accumulation was expressed as growth degree days (GDD) taking 10°C as the base temperature. The model was fitted to growth data of sorghum plants of the local landrace Ahmar (from Jazan region of Saudi Arabia) established in 60-cm deep pots filled with a sandy loam soil and irrigated and fertilized so to obtain optimum growth conditions. Heading occurred 62 days after planting (DAP), while physiological maturity was reached after 105 DAP. Evolution of plant height as a function of GDD was represented by a sigmoid model. The model was validated on growth data of field-grown plants of the same landrace. It appears that this local grain sorghum landrace has a short season given its short life cycle. However, this may vary slightly by location and year since the actual growth rate of the plant depends on several environmental factors such as soil fertility, ambient temperature, moisture availability, planting density and prevalence of pests.
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