Prediction and Prevention of Iron‐related Rice Seedling Chlorosis on Everglades Histosols

Abstract

AbstractRice (Oryza sativa L.) drill‐seeded in certain Histosols in the Everglades Agricultural Area germinates well, but after a few weeks it becomes chlorotic and grows poorly. The condition is termed “rice‐seedling chlorosis.” After flooding, chlorotic seedlings generally assume normal color, except that some seedling mortality occurs, particularly in areas with excessively deep water. Studies were conducted to identify soil and cultivar susceptibility to seedling chlorosis, and then to develop methods for preventing its occurrence. Problem soils were identified on the basis of their total Fe content. Seedling chlorosis occurred in soils containing up to 3.4 g Fe kg−1. Susceptible soils produced a nearly white ash when heated in a muffle furnace for 2 h at 550 °C. Seedling chlorosis was alleviated in all cultivars examined by drilling water‐soluble Fe compounds with the seed at rates of 20 to 30 kg Fe ha−1. The effect of seedling chlorosis on yield varied with cultivar and, to some extent, with experimental conditions. The cv. Leah was very susceptible to chlorosis, and yield was increased by Fe treatment. By contrast, even though visual symptoms were apparent, yield of cv. Labelle evidently was not reduced by seedling chlorosis because Fe treatment did not increase yield. Yield of cv. Lebonnet increased with Fe treatment in two out of three trials. Although the studies did not permit determination of the cause of seedling chlorosis, it appeared that the chlorosis did not result from a simple Fe deficiency.