The adequate disposal of chicken manure constitutes one of the premier environmental concerns of the poultry industry. Excessive nutrient (nitrogen (N) and phosphorus (P)) losses from manure amended soils have been blamed for the contamination of numerous rivers and lakes. In recent years additions of aluminum sulfate (alum) to poultry houses are being promoted as a means to reduce N losses through volatilization and phosphorus losses in the field. The potential deleterious impact that aluminum may have on crops, particularly on acid soils calls for the search of alternative amendments that could exert a similar impact on nutrient loss reduction but would also enhance the nutritional value of chicken manure. Herein we report results of a study that evaluated the effect of magnesium and aluminum sulfate, as well as mixtures of the two sources, on nutrient content and availability of chicken manure. Additions of alum caused a significant reduction of phosphorus availability (Olsen, water extractable). The effect was short-lived (than 7 days) at the lowest alum dosage (10% w/w wet basis) but persisted for more than 3 months at the highest rate (20%). Additions of magnesium sulfate - alum mixtures at certain rates exerted a similar effect on phosphorus availability than the highest alum treatment, and thus may constitute an excellent alternative for poultry manure management.