Weed control in rice is challenging, particularly in light of increased
resistance to herbicides in weed populations and diminishing availability of
irrigation water. Certain indica rice cultivars can produce high yields and
suppress weeds in conventional flood-irrigated, drill-seeded systems in the
southern United States under reduced herbicide inputs, but their response to
reduced irrigation inputs in these systems in not known. Rice productivity
and weed control by weed-suppressive cultivars and conventional
nonsuppressive cultivars were evaluated in a nonflooded furrow-irrigated
(FU) system and a conventionally flooded (FL) system under three levels of
weed management (herbicide inputs) in a 3-yr field study. Rice yields across
all weed management levels yielded ∼ 76% less in the FU system than in the
FL system. The allelopathic indica cultivar, ‘PI 312777’, and commercial
hybrid rice ‘CLXL729’ generally produced the highest grain yields and
greatest suppression of barnyardgrass in both irrigation systems. ‘Bengal’
and ‘Wells’ were the top-yielding conventional cultivars whereas ‘Lemont’
and ‘CL171AR’ yielded the least. Weed suppression by PI 312777 and CLXL729
under “medium” weed management was equivalent to that of Lemont and CL171AR
at the “high” management level, suggesting that the weed-suppressive
cultivars may be able to compensate for suboptimal herbicide inputs or
incomplete weed control.