View Abstract

LAND USE CHANGE ALTERS NUTRIENT EXPORT AND UPTAKE IN STREAMS ALONG BRAZIL’S AGRICULTURAL FRONTIER

Globally, deforestation and agricultural intensification are rapidly changing watersheds, and threaten tropical freshwater conservation. Brazilian farmers have recently come under pressure to reduce deforestation, and have intensified to soybean-maize double cropping. This requires the addition of N and P fertilizers to watersheds. However, little information on the implications for stream nutrient dynamics and the efficacy of riparian forest buffers in preventing nutrient breakthrough is available in this region of recent agricultural expansion. Using stream and groundwater monitoring and pulse additions of NO3, NH4, and PO4 to nine watersheds draining forest, soybeans, and soybean-maize agriculture in the Xingu Basin in Brazil, we asked 1) Has the annual export of inorganic N or P increased in watersheds draining soybean or soybean-maize agriculture? 2) Do riparian forests removing excess nutrient inputs?, and 3) How far will fertilizer N and P travel downstream? 3) While the annual export of N and P increased 4-fold in cropped watersheds, this resulted mainly from a 4-fold increase in stream discharge. However, pulse nutrient additions demonstrated that N has the potential to travel long distances downstream. Downstream implications are currently unknown but important to consider given the reliance of downstream indigenous communities on streams for their livelihoods.

Authors

Jankowski, K. J., USGS, USA, kathijo@uw.edu

Deegan, L. A., Woods Hole Research Center, USA, ldeegan@whrc.org

Neill, C., Woods Hole Research Center, USA, cneill@whrc.org

Macedo, M. N., Woods Hole Research Center, USA, mmacedo@whrc.org

Coe, M. T., Coe, USA, mtcoe@whrc.org

Brando, P. M., Woods Hole Research Center, USA, pbrando@whrc.org

Maracahipes, L., Instituto de Pesquisa Ambiental da Amazonia, Brazil, leonardo.maracahipes@ipam.org.br

Details

Oral presentation

Session #:015
Date: 03/02/2017
Time: 14:45
Location: 302 A/B

Presentation is given by student: No