Articles
COMPOSTING OF MEDITERRANEAN SEAGRASS AND SEAWEED RESIDUES WITH YARD WASTE FOR HORTICULTURAL PURPOSES
Article number
549_2
Pages
29 – 36
Language
English
Abstract
A mixture of Mediterranean seagrass (Posidonia oceanica) and seaweed residues with shredded municipal yard and landscape green wastes (sea residues: green waste, 1:1,v:v) was conventionally composted for 6 months using the open windrow composting system.
After this period, pile turning was stopped and the compost was allowed to mature for 2 months.
The mixture was sampled approximately every 8 weeks throughout the composting period and the changes in physical, chemical and biological properties of horticultural importance were evaluated.
Windrow temperature was also monitored over the entire composting period.
Windrow temperatures above 60 °C were limited to the first 70 days of composting and then declined gradually.
Particle size markedly decreased with time and this was reflected in the air-water relationships: higher water-holding capacity and lower aeration were observed.
The initial pH of the mixture was 7.6 and rose steadily until it exceeded 8.1. Electrical conductivity markedly increased from day 60, and the final value in the 1/10 (w/w) water extract was 7.4 dS/m.
Total N content increased slightly with time.
However, organic matter and organic C concentrations as well as C/N ratio rapidly decreased in the first 60 days of composting and stabilised thereafter.
Final organic matter content and C/N ratio in the mature compost were 48 % and 34, respectively.
NH4+-N concentration decreased and NO3–-N increased as composting proceeded.
K, Ca and Mg content remained relatively stable over time, while that of P increased slightly.
Macronutrient content of the end product was relatively low, except for Ca.
Heavy metal concentration was extremely low in the original feedstocks, and hence, in the mature compost.
A phytotoxic effect, measured with a cress and lettuce seed germination bioassay, was observed initially.
This negative effect declined in cress, but not in lettuce, as the mixture composted and matured.
After this period, pile turning was stopped and the compost was allowed to mature for 2 months.
The mixture was sampled approximately every 8 weeks throughout the composting period and the changes in physical, chemical and biological properties of horticultural importance were evaluated.
Windrow temperature was also monitored over the entire composting period.
Windrow temperatures above 60 °C were limited to the first 70 days of composting and then declined gradually.
Particle size markedly decreased with time and this was reflected in the air-water relationships: higher water-holding capacity and lower aeration were observed.
The initial pH of the mixture was 7.6 and rose steadily until it exceeded 8.1. Electrical conductivity markedly increased from day 60, and the final value in the 1/10 (w/w) water extract was 7.4 dS/m.
Total N content increased slightly with time.
However, organic matter and organic C concentrations as well as C/N ratio rapidly decreased in the first 60 days of composting and stabilised thereafter.
Final organic matter content and C/N ratio in the mature compost were 48 % and 34, respectively.
NH4+-N concentration decreased and NO3–-N increased as composting proceeded.
K, Ca and Mg content remained relatively stable over time, while that of P increased slightly.
Macronutrient content of the end product was relatively low, except for Ca.
Heavy metal concentration was extremely low in the original feedstocks, and hence, in the mature compost.
A phytotoxic effect, measured with a cress and lettuce seed germination bioassay, was observed initially.
This negative effect declined in cress, but not in lettuce, as the mixture composted and matured.
Authors
R. Orquín, M. Abad, P. Noguera, R. Puchades, A. Maquieira
Keywords
Posidonia oceanica, compost characterisation, maturity, organic waste reclamation, sustainable agriculture.
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