Relationship between drainage composition and clay minerals evolution under heavily irrigated sugarcane cultivation in southwest Iran

Abstract

The present study was conducted to determine the concentration and total amount of some compounds excreted in the drainage water of two different records of soils cultivated with sugarcane and to compare the mineral evolution of these soils with that of uncultivated soils. Cultivation changed the soil class Typic Aquisalids in uncultivated soils to Fluventic Haplustepts in cultivated soils. Unlike other elements, Ca and Mg showed a storage trend in some months. Mn and Fe depletion was largely a function of reduction conditions due to intensive irrigation, leading to high depletion in the irrigation period (80–85% of the total amount discharged). Although Si removal was a function of the irrigation period, its amount was much higher than that of Fe and Mn. However, as the irrigation record increased, more Si was removed during the irrigation period. Except for Mg, Si, Fe, and K, removal through drainage water did not depend on the length of the cultivation period. It was argued that these compounds were released due to the evolution or dissolution of clay minerals. During the irrigation period, K was removed much more than all other elements because of wetting, drying, and increasing NH4 by applying fertilizers. Si > Mg > Ca > K > Fe > Mn and K≫Si ∼ Ca ∼ Mg > Fe > Mn were the trends observed in concentration and total excreted amount in drainage water, respectively. Furthermore, minerals such as palygorskite, illite, and chlorite were abundant in uncultivated lands, but decreased or almost disappeared in cultivated lands, leading to the formation of expandable minerals such as smectite and vermiculite.