Response of Wheat Cultivars to Liming in Some High Al Oxisols of Rio Grande do Sul, Brazil1

Abstract

AbstractThe objective of this field study was to determine the yield response of wheat (Triticum aestivum L.) to the direct and residual effects of liming in relation to variety, soil acidity, Al toxicity, P availability, and disease incidence in five Oxisols of Rio Grande do Sul, Brazil under successive wheat‐soybean (Glycine max L. Merrill) cropping.This work was carried out under field conditions using various limestone treatments arranged in a randomized block design and replicated four times. Plots were 6 m long ✕ 2.4 m wide with 12 rows planted 20 cm apart at the rate of 90 kg/ha. The soils used in this investigation were in the suborder Udox.While Brazilian wheat varieties developed under acid soil conditions tended not to respond to liming due to their tolerance to exchangeable Al and possibly Mn, wheat varieties from other countries, developed under less acid soil conditions, did respond significantly to liming because of their susceptibility to soil Al and possibly Mn. Some Brazilian wheat varieties did respond to liming under high soil acidity and exchangeable Al levels. Liming to bring soil pH between 4.8 and 5.7 and reduce toxic Al levels below 1.5 meq/100 g was a more valid criterion than raising soil pH to neutrality in order to maximize yields. Liming to pH 5.7 or higher increased the incidence of Ophiobolus graminis and a soil‐borne mosaic.