Madhuram: A Simulation Model for Sweet Potato Growth

In this paper a process model for simulating the growth of sweet potato has been proposed. Vegetative developmental days (VDD) and reproductive developmental days (RDD) were calculated to predict crop phenology. Crop growth was divided into three phases, i.e., the first phase from planting to tuber initiation, the middle phase from tuber initiation to the beginning of tuber bulking and the final phase from the beginning of tuber bulking to harvest. Vine growth rates in terms of RDD were worked out for all the phases. Leaf production was assumed to be related to the length of life of individual leaves and the average leaf area was assumed to be inversely related to the number of leaves retained. A new algorithm for predicting branching events was developed. Solar radiation and photosynthesis were calculated using standard methods. Part of the photosynthates produced was used for providing energy for the maintenance and growth processes. The remaining was allocated to leaves, stem and tubers in proportion to their growth rate. The model predicted yields were in good agreement with the corresponding observed values in most of the cases. Prediction of number tubers was also reasonably accurate. However, prediction of number of leaves and branching deviated considerably from the observed value.