EFFECT OF CROP RESIDUES AND LIMING ON SOIL PHYSICAL AND CHEMICAL PROPERTIES OF TROPICAL AND TEMPERATE SOILS (ORGANIC CARBON, WATER RETENTION, WATER-STABLE AGGREGATES, BRAZIL, INDIANA)

DIMAS VITAL SIQUEIRA RESCK, Purdue University

Abstract

Fertilization and liming, as well as the return of crop residues to the soil, are essential to prevent a rapid loss of organic carbon content from cultivated soils. Tropical and Temperate soils will likely respond differently to these amendments. An incubation study was designed to test the effects of corn, soybean, or no residue additions, with or without the addition of lime, on soil physical and chemical properties of two Oxisols (virgin and cultivated) from the Cerrados region of Brazil and a Mollisol and Inceptisol from Indiana. The soil properties measured at 0, 10, 20, 30, 60 and 90 days of incubation included organic carbon, pH, cation exchange capacity (CEC), water-stable aggregation, and water retention at -10, -33, and -100 kPa water potential. Carbon dioxide evolution was measured at short time intervals throughout the 90 days of incubation. The decrease in organic carbon content with time was in the order Inceptisol > Mollisol > Cultivated Oxisol > Virgin Oxisol. Microbial activity, as measured by CO(,2) evolution rates, was almost twice as great in the Temperate soils as in the Tropical soils. The addition of lime and crop residues tended to decrease water retention capacity of the virgin Oxisol, whereas the no residue treatment was not affected by lime. Lime did not affect water retention for any crops in the Cultivated Oxisol or in the Mollisol. Time of incubation had a positive effect on soil water-stable aggregation. Lime decreased water-stable aggregation in the Virgin Oxisol when no residue was added. Corn and soybean residues improved water-stable aggregation in all four soils. The general order among soils for water-stable aggregation was Virgin Oxisol > Cultivated Oxisol > Inceptisol > Mollisol. Lime increased the CEC of the Virgin Oxisol by 92%, whereas the CEC of the Cultivated Oxisol and the Temperate soils was not significantly affected by lime.

Degree

Ph.D.

Subject Area

Agronomy

COinS