A PLANT TEST FOR DETERMINATION OF PHOSPHORUS VALUE OF URBAN WASTES

The kinetics of phosphorus release from 5 sewage sludges and 1 garbage compost was studied by a biological short and middle term test : several doses of phosphorus were supplied as urban waste, or as monocalcium phosphate in pots filled with sand and planted with ray-grass in a growth chamber.
Cultivations were continued through several cuttings until depletion of phosphorus sources.

The relative efficiencies of urban wastes phosphorus were calculated by the ratio between slopes of regression lines of cumulative phosphorus uptake to phosphorus supply, as sludge or compost on one hand, or as monocalcium phosphate on the other hand.

These relative efficiencies as a function of time were described by the following equations that account for more than 98.5 per cent of variation E = K t^c were E = efficiency (p. 100), t = time of root-phosphorus source contact in days, between some limits, k and c = special coefficients for each organic waste.

Urban wastes have to be regarded as slow releasing phosphorus fertilizers.
Sludge composted with sawdust give the higest intensity of phosphorus alimentation, garbage compost the lowest.

Symposium on Substrates in Horticulture other than Soils In Situ

B. Pommel

https://doi.org/10.17660/ActaHortic.1982.126.28