Municipal solid waste composts are often inadequately stabilized for agricu
ltural purposes. In addition, compost quality may be even more reduced by l
oss of nitrogen (N) during the composting process. We have utilized a compo
st with a high content of soluble sugars (11 mg g(-1), DM, indicating immat
urity) and a low N concentration (0.95%, DM). The compost had a low level o
f heavy metals. Results obtained in a germination bioassay conducted with c
ress, ryegrass and sunflower in a compost-sand mixture reflected the immatu
rity of the compost. Such composts should be fortified with N (in a complet
e fertilizer, when possible), at the same time avoiding an intimate contact
with the soil (e.g., plowing down). When the compost (and raw wastes and w
astes at the 4th week of composting) was mixed with a soil ata heavy rate (
2.5 % w:w), ryegrass seedling emergence in pots was not affected, but the p
lantlets' fresh weight in the compost treatment was significantly lower tha
n that in the control (soil) and lower than that in the raw wastes, probabl
y due to the lower N concentration. As expected, plantlet fresh weight was
notably increased by the combination of compost and wastes with a complete
fertilizer. The application of compost in combination with a complete ferti
lizer or urea did not affect either dry matter production or nutrient uptak
e of ryegrass, despite the combination's being applied just at sowing (in p
ots). Results obtained in these experiments indicate that combining immatur
e composts with urea [supplemented with phosphorus (P) and potassium (K), w
hen possible] at a ratio of about 50:1 (about 200 kg urea per 10 t compost)
could be sufficient to prevent negative results in crop establishment. Suc
h practices could contribute to overcoming the limited fertilizing capacity
of the composts.