ACIDIFICATION OF COMPOSTS FROM AGRICULTURAL WASTES TO PREPARE NURSERY POTTING MIXTURES

The effects of powdered elemental sulfur (S⁰) and ferrous sulfate (FeSO₄.7H₂O) on the pH 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 36% for C1, C2 and C3, respectively.
S⁰ was more efficient than FeSO₄.7H₂O for lowering the pH, and a saturation-like effect was found within the range of amendment rates studied.
The pH decrease ranged from 0.24 to 3.03 units.
This pH reduction was paralleled by an increase in compost salinity, especially with S⁰. pH declined slowly and gradually with S⁰, whereas FeSO₄.7H₂O decreased pH soon after its application, followed by a progressive increase and subsequent stabilization.
When S⁰ was added to the compost, the sulfur-oxidizing bacteria population increased from 10⁷ to 10¹⁰ CFU/g during the first 50 days of incubation, followed by a significant decrease.
This initial increase in bacterial population paralleled the pH decrease observed.

International Symposium on Growing Media

C. Carrión, M. Abad, F. Fornes, V. Noguera, R. Puchades, A. Maquieira, S. Botella, R. García

vegetable crop wastes, acidification efficiency, elemental sulfur, ferrous sulfate, microbial ecology

https://doi.org/10.17660/ActaHortic.2008.779.41