title: Impacts of management alternatives on rice yield and nitrogen losses to the environment: A case study in rural Sri Lanka.
abstract: Maintaining crop yields is vital as populations increase, but environmental degradation resulting from cultivation must be prevented. In particular, freshwater resources are at risk of nitrate leaching from superfluous fertilization. This research explores the tradeoffs between maximizing yield and limiting environmental impacts of rice production in Sri Lanka. The DeNitrification-DeComposition (DNDC) model was used to examine how various combinations of fertilization and irrigation management affect yield, nitrous oxide (N2O) emissions, and nitrogen (N) leaching in paddy systems under climate and soil conditions in the dry zone of Sri Lanka from 1991 to 2010. Simulated fertilizer application rates ranged from zero to 2700 kgN/ha and simulated irrigation schemes were continuously flooded, marginally flooded, and rain-fed. Increasing fertilizer levels from zero to 300 kgN/ha per year increased yield but application of fertilizer beyond that amount ceased to affect yield for any of the three irrigation schemes. The combination of management options for obtaining the maximum grain yield, near 9000 kgC/ha, with the greatest amount of N uptake and relatively low nitrate leaching was using 225 kgN/ha under a continuously flooded regime. This research explores how cultivation in rice-growing regions in south Asia affects the environment and the N cycle, and demonstrates how informed management of these systems can reduce external inputs of N fertilizer without impacting yield.
authors.affiliation: Vanderbilt Institute for Energy and Environment, Department of Earth and Environmental Sciences, PMB 407702, 2301 Vanderbilt Place, Nashville, TN 37240-7702, USA. Electronic address: Elizabeth.stone@vanderbilt.edu.
authors.forename: Elizabeth C
authors.initials: EC
authors.lastname: Stone
authors.affiliation: Vanderbilt Institute for Energy and Environment, Department of Earth and Environmental Sciences, PMB 407702, 2301 Vanderbilt Place, Nashville, TN 37240-7702, USA.
authors.forename: George M
authors.initials: GM
authors.lastname: Hornberger