Shade tree incorporation is beneficial in coffee cropping systems under sub-optimal conditions. This study was performed in lowland Costa Rica, at a 12-year-old experimental coffee farm. The main objective was to compare the effect of a nitrogen fixing shade tree, Erythrina poeppigiana, on nutrient availability in the rhizosphere of coffee under conventional fertilization. Accumulation of nutrients (mineral N, available P, and exchangeable base cations) in rhizosphere relative to bulk soil was greater under shade than full sun. Low nitrate availability in rhizosphere soil of full sun coffee was explained by root-induced acidification relative to bulk soil, as abundance of ammonia-oxidizing bacteria (AOB), which mediate nitrification, were positively correlated with pH. Organic fertilization enhanced AOB abundance and altered soil bacterial community structure relative to conventional fertilization. This study indicates clear effects of shade-tree presence on nutrient availability at the micro-scale, management of which is critical for stability of coffee agroforestry systems.
| Identifer | oai:union.ndltd.org:TORONTO/oai:tspace.library.utoronto.ca:1807/35655 |
| Date | 15 July 2013 |
| Creators | Munroe, Jake Warner |
| Contributors | Isaac, Marney E. |
| Source Sets | University of Toronto |
| Language | en_ca |
| Detected Language | English |
| Type | Thesis |
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