Modeling Long-grain Rice Milling Quality and Yield During the Harvest Season

Abstract

Three mathematical models were developed to predict percent milled rice (PMR), percent head rice (PHR), and field yield (FY) of long-grain varieties as a function of rice moisture content (m.c.) at harvest. The concept of potential yield was used in the model development. The actual yield was equal to the potential yield minus the yield reduction caused by specific weather conditions. The PMR and PHR models were validated using experimental data collected for three long-grain rice varieties from 1987 to l990. The potential FY model was validated using the data reported by Morse et al. (1967) and Bal and Ojha (1975). Predicted PMRs compared well with the experimental data with the average prediction errors of less than 1.9 percentage points. The average differences between the predicted and measured PHRs were less than 2.4 percentage points when rice was harvested between 13 and 24% m.c. Large prediction errors (more than 5 percentage points) were obtained in limited cases where rice was harvested at m.c.s greater than 24% or less than 13%. The predicted FYs compared reasonably well with the experimental data by Morse et al. (1967) and Bal and Ojha (1975) with the average errors of 3.5 and 6.8%, respectively.