Acidifying Composts From Vegetable Crop Wastes To Prepare Growing Media

Compost Science & Utilization, (2008), Vol. 16, No. 1, 20-29

Acidifying Composts From Vegetable Crop Wastes To Prepare Growing Media For Containerized Crops

C. Carrión1, R. García de la Fuente (1), F. Fornes (1), R. Puchades (2) and M. Abad (1)

(1) Instituto Agroforestal Mediterráneo, Universidad Politécnica de Valencia, Valencia, Spain
(2). Instituto de Química Molecular Aplicada, Universidad Politécnica de Valencia, Valencia, Spain

The effects of adding five rates of powdered elemental sulfur (S0) or ferrous sulfate (FeSO4.7H2O) on the acidification process of three alkaline composts prepared with residual vegetable crop biomass (melon, C1; pepper, C2; and zucchini, C3) were investigated. Composts reacted differently to the application of the amendments, the acidification efficiency averaging 43%, 50% and 35% for C1, C2 and C3, respectively. S0 was more efficient than FeSO4.7H2O for lowering the pH, and a saturation-like effect within the range of amendment rates studied was found. The pH decrease reached in the composts varied between 0.24 and 3.03 units. The pH reduction brought about by the amendments was paralleled by an increase in compost salinity, especially with S0. pH declined slowly and gradually with S0, whereas FeSO4.7H2O caused a rapid drop in compost pH soon after its application, followed by a progressive increase and subsequent stabilization. The drop in compost pH following S0 amendment was related to the decrease in CaCO3 contents and to the rise in CaSO4 levels. In addition, a remarkable increase in autotrophic bacteria population and a slight increase in heterotrophic bacteria along with the acidification process were recorded. Amended composts showed a range of physico-chemical and chemical characteristics suitable for use as growing media ingredients for containerized crops.

Copyright 2007, The JG Press, Inc.