ISHS Acta Horticulturae 150: International Symposium on Substrates in Horticulture other than Soils In Situ
NITROGEN CONTENT AND N-MINERALIZATION OF SEWAGE SLUDGES AS SUBSTRATES COMPONENT |
| Authors: | M.A. Garau, M.T. Felipó, J. Cardús |
| Abstract:
Municipal sewage sludge from two different wastewater-treatment plants had been analysed in order to know their nitrogen content. The total-N is higher in aerobic than in anaerobic samples and the inorganic-N is always less than 6% of total-N. The N-release of sewage sludge depends on its minéralization, so to ensure sufficient nitrogen for adequate plant growth is necessary to know the mineralizable nitrogen. The N-mineralization rate of two mentioned sewage sludges in a sandy loam soil has been measured in aerobic conditions by incubating different soil-sewage sludge mixtures at 30°C in leaching tubes and periodically extracting the mineralized nitrogen with destilled water. The water content was adjusted to 1/10 atm. by suction. The amount of mineralized-N (Nm) increase linealy with the incubation period and sewage sludge rate incorporated. From the cumulative N-mineralized along 16 succesive weeks, the mineralization potential was estimated, based on the assumption that N-mineralization follows first-order kinetics. The N-mineralization potential value (No) was used to calculate the rate constant (K) and half-time for N-mineralization (t½). The No values of the two soil sludge systems depends on the rate and the kind of sewage sludge.
The average of K is 0.020 ± 0.00003 day-1 ( | |
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= 0.05). The t½ in different soil-sewage mixtures is about five weeks.
