The removal of large masses of Egeria densa out of the lakes of Paulo Afonso hydroelectric plant complex has been problematic. Their use as organic fertilizer was compared to that of cattle manure, in an irrigated corn field. Doses of 20 and 40 t ha-1 of dry matter were compared to a control, without fertilizer. Simultaneously, decomposition of the material in the soil was monitored. The E. densa mass decomposed rapidly, with less than a third remaining after one month and less than 1% after two months. Incorporations with both E. densa and manure added large quantities of nutrients to the soil and resulted in larger grain (3.5 to 8.5 t ha-1) and straw (4.3 to 8.8 t ha-1) productions than those of the control (0.3 and 1.2 t ha-1). Productions with E. densa (grain, 7.7 t ha-1), on average, were higher than those with manure (4.2 t ha-1), without significant difference between doses, probably because the mass of E. densa releases nutrients faster than that of manure. The content of heavy metals and other elements in the mass of E. densa were within the range approved for organic fertilizers and did not affect the corn plants. Using the masses of E. densa as organic fertilizer appears to be a recommendable practice.
weed; aquatic plant; organic fertilizer; nutrients; corn
