Many people ask why continue mundane planting date research donâ€™t we have enough. Truth is, when talking about items such as planting date, and soil testing data that will be modeled, there is never enough data. The more data you have, the better the recommendation we as agronomists can give a producer. From 2006 until his recent departure Dr. Tim Walker has conducted planting date research on rice in Mississippi. Over that 8 year span he generated a wealth of data that we modeled to determine optimum planting dates for rice grown in the Delta. The figure presented illustrates those 8 years of data.
What does the planting date data tell us? Over the last eight years the optimal time to plant rice or the sweet spot for Clearfield and/or conventional varieties has been sometime between March 20 and April 30 without a measured reduction in yield potential. This model takes into account the years were we observed a great amount of heat stress at flowering and years like last year where we had very cool average summer temperatures. The good news is the observed decline in relative yield is not that steep with slightly over a quarter percent yield loss per day after April 30. Therefore based on eight years of data in Mississippi if our planting dates are pushed two weeks past April 30 due to weather issues, our yield loss from planting late would be less than 5%. Flashback to 2013, (Blue diamonds on figure) Mississippi experienced a very similar planting season as we are currently facing in 2014. The Planting dates where the greatest yield potential was achieved (>95%) occurred on April 29 and May 16. Therefore if the start of 2014 reflects 2013 and if the rest of the year follows, we should have a few more weeks to get the rice crop in the ground with minimal risk of starting off with a yield penalty. This data represents only Clearfield and/or conventional varieties.
Mississippi does have limited observations on Hybrid rice planting dates that suggest the critical planting window for hybrids is slightly longer than that of Pure lines. So keep in mind a quote from Dr. Walker in the January Issue of Rice Farming â€œHybrids offer the biggest advantage over pure lines when produced under stressful environments. Therefore, for growers who mix pure lines and hybrids, I recommend starting with pure lines and finishing with hybrids.â€