The objective of this work was to quantify changes on carbon and nutrient contents in soils under continuous manure additions. Eighteen cropped fields that had received annual additions of manure for at least two years and four fields under pasture with no history of manure addition were sampled to assess if this practice results in the accumulation or losses of added nutrients. Soils samples from the 0-20, 20-40 and 40-60 cm layers were taken from each field, and analyzed with regard to their physical (particle size and soil density) and chemical (pH, total C, N and P, extractable P by Mehlich-1 and water, and exchangeable cations) properties. Manure samples used in nine fields were also analyzed for chemical composition. Manure additions resulted in a build up of nutrient stocks near to 20 Mg ha-1 of C, 2 Mg ha-1 of N and Ca, and 0.5 to 1 Mg ha-1 of P, K and Mg (0-60 cm). Water-soluble P concentrations of 7 mg kg-1 in the 40-60 cm layer indicated losses of this nutrient, the less mobile in soils. Accumulation of exchangeable cations in the 0-60 cm layer, in comparison with control areas, indicates an even greater potential for losses of these nutrients.
subsistence agriculture; organic amendments; phosphorus lixiviation
