International Journal of Agricultural Sustainability
International Journal of Agricultural Sustainability 2 (2004) 33–42
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Gliricidia sepium Carbon Inputs and Soil Carbon Pools in a Costa Rican Alley Cropping System
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Maren Oelbermann1, R. Paul Voroney2 and Donald C. L. Kass3,4
1Department of Earth Sciences, University of Waterloo, Waterloo, ON, Canada; 2Department of Land Resource Science, University of Guelph, Guelph, ON, Canada; 3Area de Cuencas y Sistemas Agroforestales, CATIE, Turrialba, Costa Rica; 4Current Address: Northeast Regional Laboratory, Food and Drug Administration, Department of Health and Human Services, Jamaica, NY, USA
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Abstract
Alternative land management practices, including agroforestry, help to maintain levels of soil organic matter (SOM) and can facilitate soil carbon (C) sequestration for mitigating atmospheric CO2 emissions. This study quantified C inputs and determined the changes of the soil C pool in a 19-year-old Gliricidia sepium alley cropping system, studied at two fertiliser levels (tree prunings only [-N], and tree prunings plus chicken manure [+N]), and was compared to a sole crop system. Carbon input from tree prunings ranged from 455 to 457 g C m-2 y-1, whereas C inputs from crop residues were similar between alley- and sole crops ranging from 121 to 159 g C m-2 y-1. The soil organic C (SOC) pool in the alley crop was 16–23% higher than the sole crop. In the 19th year of alley farming, SOC was significantly higher (p < 0.05) in the alley crop (3.2%) compared to the sole crop (2.4%), and was also greater compared to that at the time of establishment of the agroforestry system (2.8%). Gross SOC turnover to a 20-cm depth ranged from 12 to 14 years in the +N and -N alley crops compared to 49 and 50 years in the +N and -N treatments for the sole crops. Residue stabilisation efficiency in the alley crops was 39% and 55% in +N and -N treatments respectively.
Keywords: agroforestry systems, carbon inputs, gross soil organic carbon turnover, mulch, soil carbon, residue stabilisation efficiency
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