Sterility in Rice Cultivars as Influenced by MSMA Rate and Water Management¹

Abstract

In recent years an expansion of rice (Oryza sativa L.) acreage in Arkansas has resulted in rice being produced on soils with a history of cotton production. Most of these cotton soils have had repeated applications of monosodium methanearsonate (MSMA) as a herbicide. There is some evidence that arsenical residues in the soil can lead to sterility in rice. In an effort to answer this question, we conducted a field experiment on a Crowley silt loam soil (Typic Albaqualf) in 1975 to evaluate the influence of MSMA on plant growth and yield of rice. Treatments included two water management regimes (continuous flood vs. one drain and dry), three levels of MSMA [0, 1.1, and 11.2 kg/ha of arsenic (As)] and 15 rice cultivars and experimental strains differing in susceptibility to straighthead disease (abnormally developed or sterile flowers resulting in reduced grain yields). Soil samples taken 65 days after arsenic application showed that As remained in the rice root zone. Vegetative growth prior to panicle initiation was not affected by any of the treatments; however, visual observations made near maturity showed that where MSMA had induced sterility, the plants were dark green suggestive of straighthead. Reproductive growth as shown by panicle weights and sterility ratings was affected most by high MSMA rates and continuous flooding. Under continuous flood, panicle weights were reduced and sterility ratings increased as MSMA rate increased. This effect was more pronounced in cultivars most susceptible to straighthead and was minimized by draining the flood and drying the soil. This data suggests that the MSMA residues induced straighthead. A significant and similar relationship was found between panicle weights and sterility ratings at maturity for both water management regimes.

Growing Rice Aerobically Markedly Decreases Arsenic Accumulation

“…Chemical transformation in soil is, therefore, the dominant reason for a greatly enhanced As assimilation in paddy rice compared with other cereals such as wheat and barley (19). In support of this conclusion, earlier studies showed that As-induced "straighthead" symptoms in rice were found to occur only under flooded conditions, and not in rice grown under aerobic conditions (25,26).…”

Market Basket Survey Shows Elevated Levels of As in South Central U.S. Processed Rice Compared to California: Consequences for Human Dietary Exposure

“…Old cotton soils are now being used to produce rice due to an expansion in rice acreage (11). Arsenical pesticide usage in the U.S. is high in traditional cotton (Gossypium spp.)…”

The influence of chemical form and concentration of arsenic on rice growth and tissue arsenic concentration

“…Arsenic accumulation in soils reduces soil productivity (Liebig, 1966) and is toxic to plants (Baker et al, 1976;Deuel and Swoboda, 1972;Schweizer, 1967). In the southern United States, for example, As toxicity has been associated with straighthead, a physiological disease of flooded rice (Gilmour and Wells, 1980;Marin, 1989;Wells and Gilmour, 1977). Straighthead results in blank florets, distorted palea and lemma and, in extreme cases, failure of panicles to form (Johnston et al, 1959).…”