es500338u_si_001.pdf (1.66 MB)
Sealing Rice Field Boundaries in Bangladesh: A Pilot Study Demonstrating Reductions in Water Use, Arsenic Loading to Field Soils, and Methane Emissions from Irrigation Water
journal contribution
posted on 2014-08-19, 00:00 authored by Rebecca B. Neumann, Lara E. Pracht, Matthew
L. Polizzotto, A. Borhan M. Badruzzaman, M. Ashraf AliIrrigation
of rice fields in Bangladesh with arsenic-contaminated
and methane-rich groundwater loads arsenic into field soils and releases
methane into the atmosphere. We tested the water-savings potential
of sealing field bunds (raised boundaries around field edges) as a
way to mitigate these negative outcomes. We found that, on average,
bund sealing reduced seasonal water use by 52 ± 17% and decreased
arsenic loading to field soils by 15 ± 4%; greater savings in
both water use and arsenic loading were achieved in fields with larger
perimeter-to-area ratios (i.e., smaller fields). Our study is the
first to quantify emission of methane from irrigation water in Bangladesh,
a currently unaccounted-for methane source. Irrigation water applied
to unsealed fields at our site emits 18 to 31 g of methane per square-meter
of field area per season, potentially doubling the atmospheric input
of methane from rice cultivation. Bund sealing reduced the emission
of methane from irrigation water by 4 to 19 g/m2. While
the studied outcomes of bund sealing are positive and compelling,
widespread implementation of the technique should consider other factors,
such as effect on yields, financial costs, and impact on the hydrologic
system. We provide an initial and preliminary assessment of these
implementation factors.