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GLEAMS evaluation in potato fields for agricultural nutrient management in central Bolivian highlands

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  21st Century Watershed Technology: Improving Water Quality and Environment Conference Proceedings, 21-24 February 2010, Universidad EARTH, Costa Rica  701P0210cd.(doi:10.13031/2013.29452)
Authors:   Sarah Walker, Conrad D Heatwole, Jaime Cossio
Keywords:   Nutrient management, GLEAMS model, mineralization, Andes, Bolivia, potato

An increase in population in rural agricultural communities and higher demand for food throughout Bolivia create the need for increased agricultural production. The objective of this study was to assess the suitability of the GLEAMS model as a tool for evaluating fertilization and cropping system practices for potatoes in the Andes of central Bolivia. Model evaluation was based on comparison with field data from three experimental plots, with measurement of soil total Kjeldahl N, crop production, crop N uptake, and crop P uptake. The general trend of model prediction followed expected patterns of nutrient dynamics, however the predicted crop dry matter production and N uptake were lower than observed values. The root mean square standard deviation ratio (RSR) and percent bias (PBIAS), respectively, for soil total Kjeldahl N concentration were 7 and -2%. The PBIAS for total crop dry matter production was 39%. The PBIAS for total crop N uptake was 54% and for total crop P uptake was -2%. Evaluation of the various N pathways pointed to low mineralization rates as the key component causing the poor predictions. Since agricultural production in this region of central Bolivia is highly dependent on organic N from soil and applied animal manure, the mineralization processes in GLEAMS must be further evaluated and improved before the model should be applied in this region.

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