Herbicide and winter flood treatments for controlling volunteer rice off-season

Abstract

Field experiments were conducted to study the efficacy of 12 herbicide treatments for volunteer rice control with, or without, winter-flooding in Stuttgart and Rohwer, Arkansas, USA over two years (2012–13 and 2013–14). Herbicides were applied either in the fall or at 35 d prior to planting rice in the spring. Commercially harvested Clearfield™ long-grain inbred rice 'CL152' was used as volunteer rice seed, broadcasted and lightly incorporated in October, 2012 and 2013. 'Jupiter' (medium-grain inbred, conventional rice) was planted in May as the rice crop. Winter-flood was initiated soon after the fall herbicide treatments were applied and terminated in February. Winter-flood reduced volunteer rice germination by 34% in 2013 and by 40% in 2014. Some fall herbicide treatments, without winter flood, generally caused more injury to the rice crop planted in the spring than the winter-flooded treatments. Fall application of pyroxasulfone (0.12 kg ha−1), flumioxazin (0.14 kg ha−1), and sulfentrazone (0.34 kg ha−1) as well as pre-plant application of pyroxasulfone (0.12 kg ha−1) and 2,4-D (2.24 kg ha−1), resulted in lower volunteer rice infestation, averaged over flood treatments. Pre-plant application of 2,4-D (2.24 kg ha−1), sulfentrazone in the fall (0.34 kg ha−1) and pyroxasulfone pre-plant (0.12 kg ha−1) injured the rice crop by 20%, 23%, and 47%, respectively. Fall application of pyroxasulfone (0.12 kg ha−1) followed by a lower rate of 2,4-D (1.12 kg ha−1) 35 d pre-plant caused minimal (6%) crop injury and did not reduce yield. This treatment provided better volunteer rice control (73%) than pyroxasulfone alone at 0.12 kg ha−1 applied in the fall (64%). To evaluate the overwintering potential of hybrid and non-hybrid volunteer seeds, these seed types were planted at three depths (0, 7.5, 15 cm) in flooded and non-flooded conditions in a buried-pot experiment at Stuttgart and Rohwer over 2 years. Winter-flood reduced rice germination by 50% in 2013–14 and 40% in 2014–15 (averaged over seed type and burial depth), after 160 d and 130 d of burial, respectively. After the winter, the viability of hybrid seed (germinable + dormant) was higher (13 and 53%) than that of non-hybrid seed (8 and 27%) in both years.