G Pellejero - CURZA, Universidad Nacional del Comahue, Esandi y Ayacucho S/N, ۸۵۰۰ Viedma, Rı´o Negro, Argentina
A Miglierina - Dpto. Agronomı´a, Universidad Nacional del Sur, Av. Alem ۱۲۵۳, ۸۰۰۰ Bahı´a Blanca, Buenos Aires, Argentina
G Aschkar - CURZA, Universidad Nacional del Comahue, Esandi y Ayacucho S/N, ۸۵۰۰ Viedma, Rı´o Negro, Argentina
M Turcato - CURZA, Universidad Nacional del Comahue, Esandi y Ayacucho S/N, ۸۵۰۰ Viedma, Rı´o Negro, Argentina
R Jime´nez-Ballesta - Dt۸ Geologı´a y Geoquimica, Universidad Auto´noma de Madrid (UAM), Ciudad Universitaria de Cantoblanco,۲۸۰۴۹ Madrid, Spain

Purpose Farming production in the lower part of Rı´oNegro Valley (Argentina) has increased considerably duringrecent years, causing soil degradation and, specifically,decreasing the organic matter contents. This fact requiresrecovery measures, as organic amendments for soils, toimprove its quality. The marked objectives for the presentresearch is to evaluate compost as organic fertilizer, basedon a mix of onion waste and bovine manure.Methods The experiment was carried out in a completelyrandomized design, involving five treatments and onecontrol, with ten copies of each one. Tests were performedin a greenhouse, using flowerpots and experimental plots,in a typical soil of the region (Aridisol), pH 8.3 and 2.2%of organic matter, mixed with different compost dosages(20, 40, 60 and 80 Mg ha-1) and the chemical treatment,Urea (0.26 Mg ha-1). A horticultural farming of 1 lettucewas sowed (Lactuca sativa). A conventional handling wascarried out for the whole cultivation period, and at the endwas harvested. Ten plants per plot were taken and weredetermined total fresh weight, aerial part fresh weight, rootpart fresh eight. In the dry controls total dry weight, aerialdry weight and root dry weight was determined.Results Results show, with an error (p.05), significantdifferences in the fresh weight per plant calculated,between treatments and control; a noticeably greater effectcan be observed in the treatments with 6 and 8 kg m-2compost amending and urea treatment. There is no evidenceof the existence of significant differences (p.05)between treatments and control, according to the valuesobtained for root size as well as aerial dry weight and rootdry matter.Conclusions It can be concluded that the addition oforganic fertilizer to soils, has positive effect on the Freshweight of the plant, recommending the use of doses of6 kg m-2 while the dose of 8 kg m-2 could replace the useof chemical fertilizers such as Urea.

Organic amendments Compost application Cultivation Horticultural production