Laboratory assays on the effects of aerated compost tea and fertilization on biochemical properties and denitrification in a silt loam and bt clay loam soils

Abstract

Aerated compost tea (ACT) is gaining interest as a nutrient amendment for urban trees. This study examined the effects of ACT, synthetic fertilizer, and deionized water on 15 biochemical properties with two soil types. Significant effects for pH, Mg 2+, Na +, C, N, and C/N ratio were not observed among treatments. No differences between dilute ACT (ACTd) at 22.4 kL ha -1 and water were detected. Soil K+ was greater with ACT concentrate (ACTc) at 224 kL ha -1 compared to 30-10-7 fertilizer at 195 kg N ha-1 with A horizon soils. Soil K+, NH4+, and microbial respiration were greater with ACTc compared to water in A soils. Soil P (A soils only), NO 3- (Bt soils only), dissolved organic N, microbial biomass N, and N mineralization were greater with fertilizer compared to ACT. Increases in denitrification were seen with ACTc compared to fertilizer and water in the first 24 hours (+4 to +12 mg N 2O kg -1), but greater increases were observed with fertilizer at hours 48 and 96 (+65 to +127 mg N2O kg-1). Greatest improvements in soil fertility were observed with fertilization. Minor improvements in soil fertility were observed with ACTc, and denitrification losses were lower with ACTc compared to the fertilizer. © 2011 International Society of Arboriculture.