COMPOST SCIENCE AND UTILIZATION, vol. 6 (pp. 74-81) JG PRESS, INC

Large quantities of green seaweed, linked probably to eutrophication, are cast ashore every summer on the Puerto Madryn beaches (Patagonia, Argentina, 42 S, 65 W). This algal biomass interferes with recreational uses of the beach, and therefore must be periodically collected and disposed. Part of this algal biomass was composted with the objective to produce an amendment to improve physical and nutritional characteristics of some local soils used in intensive agriculture, and at the same time to find a way to reduce environmental pollution. The compost was then biologically evaluated by determining the growth rate of tomato plants cultivated on various substrata (washed sand, sandy loam soil, and sandy loam soil plus inorganic fertilizers) to which different doses of compost were added. Results showed that in all cases, the addition of compost increased water holding capacity and plant growth. The increase of tomato plants was proportional to the compost doses. Also, plants grown on substrata containing at least 10 % compost had significant benefits compared to control plants, improving growth and water stress resistance. Although the quality of this compost was limited by excessive amounts of sand and low nitrogen content, it proved to be a good amendment that improved both physical and nutritional characteristics of local sandy loam soils used in intensive agriculture. According to these results, composting is a useful technique to solve environmental pollution problemas and to produce a valuable organic fertilizer for soils.