Rice Grain Yield As Affected by Seeding Date.

Seeding date is an important consideration for southern USA rice production. The objective of this research was to quantify planting date influence and compare the optimum planting window in recent years to those reported a decade ago. Experiments were conducted in Crowley, LA, and in Stoneville, MS. Planting dates ranged from mid-February to early July in LA, and from late March to early June in MS. The experiment was analyzed as a randomized complete block. Each year and state combination contained at minimum five planting dates.  Planting date substantially impacted relative grain yields in Louisiana.  Maximum (95% RY or greater) yields were achieved in LA over varying planting windows from 2009 – 2011.  Rice planted before 21 Mar achieved ≥ 95% RY in 2009, 93% in 2010, and only 82% in 2011.  Relative rice grain yield declined linearly over time for Louisiana experiments. Planting date affected RY in Mississippi also.  In 2009, ≥ 95% RY could be achieved at any planting date prior to early June and in all three years  ≥ 95% RY was achieved when rice was planted by April 5. Similar to Louisiana, RY typically decreased in a linear manner in Mississippi.  In LA, 95% RY could be achieved if planting occurred by April 9 a decade ago; however, these current data suggest that rice had to have been planted by March 20^th to achieve 95% or greater RY.  In Arkansas, the optimum planting date for 100% RY was April 12 a decade ago and in the similar latitude of Mississippi, except for 2009, rice had to be planted by April 5 to achieve 95% RY whereas 100% RY was achieved by planting March 24.  If climate change is indeed occurring, it is imperative to continue to investigate the optimum planting window to maximize grain yield potential.