| The activities of six enzymes involved in C, N, P, and S cycling were assayed in 10 surface soils each from Iowa and Costa Rica before and after waterlogging for times ranging from 0 to 6 days at 25;The effect of crop residue addition (alfalfa (Medicago sativa), corn (Zea mays L.), and soybean (Glycine max. L. Merr.)) on enzyme activities of two soils each from Iowa and Costa Rica was studied after preincubation at 25;The effect of crop rotations on enzyme activities was studied in soil samples obtained from three research sites in Iowa: at Kanawha, Sutherland, and Nashua. The sites have been under crop rotation experiments since 1954, 1957, and 1978, respectively. In general, the rotations corn-oats-meadow-meadow, corn-corn-oats-meadow, and corn-soybean-corn-soybean resulted in greater soil enzyme activities than those of continuous corn.;The effect of crop residue addition on enzyme activities was studied in two soils each from Iowa and Costa Rica treated with crop residues (alfalfa, corn, and soybean) and incubated at 25;Waterlogging of soils, crop rotations, and soil management practices markedly affected the reaction rates of enzymes and, possibly, nutrient cycling. |
