A Comparative Study of Bermudagrass Grown on Soils Amended with Aerobic or Anaerobically Digested Sludge

Abstract

AbstractA greenhouse pot experiment was conducted in which bermudagrass [Cynodon dactylum (L.) Pers.] was grown on Holtville silty clay and San Emigdio fine sandy loam soils, which were amended with aerobically (AEDS) and anaerobically (ANDS) digesed sludges to supply N at 600, 900, and 1200 kg ha−1. Ammonium sulfate [(NH4)2SO4] was applied to other pots at rates to supply N at 300 and 600 kg ha−1. A second 600 kg N treatment as (NH4)2SO4 was applied in three split applications. All (NH4)2SO4 treatments received 60 kg of P as monocalcium phosphate (MCP). Cumulative yields of bermudagrass grown on aerobic sludge treatments were greater than those yields on anaerobic sludge treatments for both soils. Patterns of plant yields indicate that a large initial release of plant‐available N occurred in aerobic sludge treatments relative to anaerobic treatments. Though not statistically significant, more N was accumulated by plants grown on aerobic than on anaerobic sludge‐amended soils. On both soils, aerobic sludge‐P was more plant‐available than anaerobic sludge‐P. Calculated recoveries of sludge‐applied N and P showed little variation due to soil type at equal rates of sludge application. For both soils, 1 Mg of aerobic sludge or anaerobic sludge produced bermudagrass yields equivalent to those resulting from the application of 24–37 kg (NH4)2SO4‐N and 7–10 kg (NH4)2SO4‐N, respectively. Tissue concentrations of Cd were below 9 × 10−4 mmol kg−1 for all treatments, and were not considered to be excessive.