Effect of iron toxicity on rice growth in sulfato-ferruginous lowland of South Senegal

Abstract

Rice production in southern Senegal is mainly rain-fed and faces numerous constraints, including iron toxicity. The objective of this study was to determine the effect of iron toxicity on rice yield in Southern Senegal. The study was carried out in farmers’ fields in the area of Sindone where two sites were selected (Sites A and B). In each site, six farmers’ rice fields covering 2000 to 2500 m2 were selected: three fields with apparent iron oxide (rust) located in lowland and three fields without iron oxide located in highland. Within each of these fields, three plots with dimensions of 300 m2 were delimited and used for the experiment for a total of 18 plots (6*3). Soil cores were taken from all plots in the 0 – 10 cm horizon at 0, 30, 60 and 90 days after rice transplanting (DAT) to measure soil pH. The intensity of iron toxicity was evaluated on rice plants at different dates and rice yield was determined at harvest at 90 DAT. At 0 and 90 DAT, pH was more acidic compared to 30 and 60 DAT for all plots. Besides, in plots affected by iron oxide, pH at 0 and 90 DAT was statistically more acidic (p < 0.01) than pH in non-affected plots. In those plots, despite normal growth and tillering, it was only at 90 DAT that brown spots appeared at the tip of the oldest leaves. In plots affected by iron oxide, at 30 DAT, symptoms of iron toxicity appeared and intensified at 60 and 90 DAT; growth and tillering were reduced with many leaves becoming discolored at both sites. Rice yield decreased by at least 43% in plots affected by iron oxide for sites A and B. Amendments that will reduce soil acidity would be recommended, this will also improve rice nutrients and increase rice yield.