Temporal Stability of Rice Grain and Whole Kernel Milling Yield is Affected by Cultivar and Date of Planting.

     Rice (Oryza sativa L.) grain yield stability is of utmost importance to rice producers, who are financially obligated in advance of the harvest, and to global rice consumers, who are subject to market volatility when rice production and supply are uncertain.  The objectives of this research were to evaluate rice cultivar stability and dates of planting and to characterize different planting dates for their consistency in grain yield and whole kernel milling potential.  Eight rice cultivars and seven planting dates were evaluated from 2003 to 2005 for a total of 19 year x planting date environments.  The coefficient of variation of cultivars and planting dates were compared to determine cultivar stability and consistency among cultivars for different planting dates.  Planting date was the most significant component of the total variation in grain yield due to environment while year, as a source of variation, was more significant for whole kernel milling yield.  ‘Jupiter,’ a medium-grain type, was the highest yielding cultivar in the study but was also one of the least stable as evidenced by a relatively large coefficient of variation.  ‘Cypress’ and ‘CL161’ were among the most stable cultivars and exhibited high grain and whole kernel milling yields suggesting that they would be ideal cultivar selections for planting at less than optimum times or when abnormal conditions occur for rice planted during the recommended timeframe.  Based on high grain and whole kernel milling yields and consistent performance across years and cultivars, the optimum date for planting rice at the Rice Research Station near Crowley, LA was 15 April.