The effect of drainage on physiological disorders of rice grown on the sub-coastal plains of the Adelaide River, N.T

Abstract

Rice grown on the heavy clay soils of the subcoastal plains of the Adelaide River, N.T., under continuous flooding suffers from leaf chlorosis, premature leaf senescence, root rot, lodging, and low yields. The effect of drainage on the observed symptoms, plant nitrogen, and carbohydrate fractions, iron, manganese, and phosphorus, and on soil Eh, pH, iron, manganese, and nitrogen was investigated for two varieties under two drainage regimes, and compared with continually flooded rice. Draining the rice twice between the start of flooding and ear initiation prevented severe soil reduction and the onset of the symptoms. Yellowing and premature leaf senescence, which started four weeks after flooding, were associated with ferrous iron toxicity in the plants, and it is highly probable that sulphide toxicity from about the time of ear initiation onwards also contributed to root rot, lodging and low yields.