Use of urea to correct immature urban composts for agricultural purposes

Citation
F. Madrid et al., Use of urea to correct immature urban composts for agricultural purposes, COMM SOIL S, 31(15-16), 2000, pp. 2635-2649
Citations number
25
Categorie Soggetti
Environment/Ecology
Journal title
COMMUNICATIONS IN SOIL SCIENCE AND PLANT ANALYSIS
ISSN journal
00103624 → ACNP
Volume
31
Issue
15-16
Year of publication
2000
Pages
2635 - 2649
Database
ISI
SICI code
0010-3624(2000)31:15-16<2635:UOUTCI>2.0.ZU;2-B
Abstract
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.