ANIMAL-BASED AGRICULTURE, PHOSPHORUS MANAGEMENT AND WATER QUALITY IN BRAZIL: OPTIONS FOR THE FUTURE

Authors: SHIGAKI, FRANCIROSE - UNIV OF SAO PAULO; Sharpley, Andrew; PROCHNOW, LUIS - UNIV OF SAO PAULO

Submitted to: Scientia Agricola
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/18/2006
Publication Date: 5/2/2006
Citation: Shigaki, F., Sharpley, A.N., Prochnow, L.I. 2006. Animal-based agriculture, phosphorus management and water quality in Brazil: Options for the future. Scientia Agricola. 63(2):194-209.

Interpretive Summary: Major changes in crop and animal production systems have taken place over the last 10 to 20 years on a global scale. Both crop and animal production has become more intensive and specialized to meet population demands for low-cost yet high quality grain and protein sources. These systems now exist in spatially separate areas because of cheap and effective transport networks that operate across regions and even countries. This has led to the one-way transfer of phosphorus (P) from areas where rock P deposits are mined to areas of grain production to animal rearing facilities, where there is a consequent accumulation of P in manures. Brazil is no exception, with the major proportion (75%) of the country’s swine and poultry production now occurring in the South and Southeast regions. We estimate that these animals produce 2.5 million tonnes of P in manure each year, nationally. Although there have been many studies on the effects of land applying manure and P on soil fertility and crop production, some of which we have presented, little information exists on resulting water quality impacts. We have demonstrated that this information is clearly needed to develop conservation practices that will minimize the potential for P runoff under Brazilian farming conditions. Although lessons can be learned from other regions of the world, conservation practices must be tailored to local land and economic constraints.

Technical Abstract: Eutrophication has become a major threat to water quality in the U.S., Europe, and Australasia. In most cases, freshwater eutrophication is accelerated by increased inputs of phosphorus (P), of which agricultural runoff is now a major contributor, due to an intensification of crop and animal production systems since the early 1990s’. As little information is available on the impacts of Brazilian agriculture in water quality, recent changes in crop and animal production systems in Brazil were evaluated in the context of probable implications to the fate of P in agriculture. Between 1993 and 2003, there was a 33% increase in the number of animals (i.e., beef, dairy cows, swine, and poultry), with most in the South Region (i.e., Paraná, Rio Grande do Sul, and Santa Catarina), where 43 and 49% of Brazil’s swine and poultry production is now located. An estimated 2.5 million tonnes of P in swine and poultry manure were produced in 2003. Most was produced in the South and Southeast regions of Brazil (62%), which represent only 18% of Brazil’s land area. In the context of crop P requirements, there was 2.6 times more P produced in manure (1.08 million tones) than applied as fertilizer (0.42 million tonnes) in the South region in 2003. If it is assumed that fertilizer P use represents P added to meet crop needs and also accounts for P sorbed by soil in unavailable forms each year and if swine and poultry manure were to replace fertilizer, then there would be an annual P surplus of 0.66 million tonnes in the South region alone. These approximations and estimates clearly highlight that, as in other parts of the world, there is a potential for surplus P to quickly accumulate in certain regions of Brazil. Unless measures are developed and implemented to utilize manure P, repeated annual surpluses will create an increasingly difficult problem to solve.