Differential Response of Cotton and Peanuts to Subsoil Acidity1

A series of experiments was conducted to compare the effects of subsoil acidity on cotton (Gossypium hirsutum L.) and peanuts (Arachis hypogaea L.). A strongly acid (pH 5.0) Norfolk sandy loam subsoil reduced cotton yield by one‐third in a field experiment but had no detrimental effect on peanut yield. Cotton roots were unable to penetrate the most acid subsoil in this experiment, whereas peanut roots appeared to be undaunted by the acidity. Growth‐chamber experiments with acid Norfolk and Greenville subsoil materials showed cotton root‐growth to be almost completely inhibited by soils that had no apparent detrimental effect on peanut roots Nutrient‐solution experiments showed that cotton roots created a more acid root environment than did peanuts; these experiments also showed that peanuts had a greater propensity for preferential absorption of lower valency ions to the exclusion of higher valency ions. Either or both of these phenomena could explain the greater tolerance of peanuts to low soil pH and its associated high soil solution aluminum.