Soil Type and Wetness Affect Tint of Peanut (Arachis hypogaea L.) Pod Shell

Abstract Peanut (Arachis hypogaea L.) is a globally important legume crop that is utilized fresh, roasted, or pressed for oil products. A substantial market exists for in-shell peanuts, and shell color is an important factor affecting price — consumers favor bright yellow. Field observations have indicated that the type of soil in which the peanut pods develop can affect shell color and tint. Field and greenhouse experiments in which plants were grown in sandy soil while pods were allowed to develop in various tested soils verified this primary observation: sandy soils resulted in bright-yellow shells, dark soils (such as peat) resulted in a darker shell color, while loess soils resulted in intermediate shell colors. Incubation of peanut pods in saturated soil solutions or filtered soil extracts inferred the existence of two opposing processes that may affect shell color: adherence of water-soluble soil components to the shell surface, and the washing-off of shell material from this surface. Overhead irri...