Salinity Effects on Rice after the Boot Stage1

Abstract

AbstractEffect of salinity on rice (Oryza sativa L.) after the boot stage has been controversial in the literature. Some authors maintain that rice is sensitive to salt at flowering, whereas others have found no evidence to support these views. The present greenhouse study evaluates the interaction after the boot stage of salinity, soil texture, and rate of drainage on rice development. Breeding line IV 213 was transplanted into 11‐liter pots filled with either silty clay or silt loam soil and irrigated with Colorado river water, S1 (EC = 1.4 mmho/cm), until after the boot stage. Then pots were irrigated until harvest with S1, S2 (EC = 4.0 mmho/cm), and S3 (EC = 8.0 mmho/cm) under the following three drainage rates from the bottom of the pots: 0, D0; 100, D1; and 200 ml/day, D2. The pots soils were always submerged and treatment water was added to replenish water lost by ET and internal draining.Soil and plant analyses showed that: Average salinities in the root zone were 2 to 4 times the salinities of the respective irrigation waters. In general, salinities increased with plant development and with decreasing rate of drainage. Salt components added to Colorado river water increased in both straw and grain without effect on yield. Mature grain yield of S1 and S2 did not differ significantly; average grain yield of S3 was 84% of S1 More reduction in yield would be expected if rice was sensitive to salt after the boot stage. Average grain yield on silty clay soil was 16% higher than on silt loam soil. Neither straw yield nor ratio of aborted to mature grain differed significantly among the various treatments. Also rate of drainage had no appreciable effect on concentration of soluble Fe, Mn, or dissolved O2 in the soil solution. The unexpected effect of rate of drainage was probably due to frequent replenishment with fresh irrigation water.