Linking carbon inputs to sustainable agriculture in Canadian and Costa Rican agroforestry systems



Oelbermann, Maren

Journal Title

Journal ISSN

Volume Title


University of Guelph


Alternative land management practices, including agroforestry, can rejuvenate marginal soils and increase soil C sequestration to help mitigate atmospheric CO2 emissions. The objective of this study was to quantify C inputs in temperate and tropical alley cropping systems. In Costa Rica 18, 9 and 3-year old 'Erythrina poeppigiana' (Walp.) O. F. Cook and 'G. sepium' (Jacq.) Walp. were combined with maize and beans ('Phaseolus vulgaris' L.), and in Canada 12-year old hybrid poplar ('Populus deltoides' x 'nigra' DN 177) was alley cropped with maize ('Zea mays' L.) and soybeans [('Glycine max' L. (Merr.)]. The 18 and 9-year old tropical system, with either tree species, had an input of 2365 and 3960 kg C ha -1 y-1 from maize and bean residues, where maize roots contributed approximately 14% of total residue C input and bean roots contributed 12%. Comparatively crop C input in Canada was 2118 kg C ha-1 y-1 for maize and 826 kg C ha-1 y-1 for soybeans, where roots contributed 10 to 14% of the total C inputs. A higher C input from crop residues in the tropical biome results from two cropping seasons per year compared to a single crop in the temperate system. Carbon input from 18-year old tree prunings was 4003 kg C ha-1 y-1, and 1038 and 1038 kg C ha-1 y-1 for 9 and 3-year old trees. Annual C input from hybrid poplar prunings was 1407 kg C ha-1 y-1 with an additional contribution of 816 kg C ha-1 y-1 from autumnal litterfall within 3.5 m of the tree row. Soil organic C (SOC) ranged from 139, 101 to 96 Mg C ha-1 y-1 for 18, 9 and 3-year old tropical systems, whereas the temperate system SOC pool was 125 Mg C ha-1 y-1. The proportion of C derived from C4 plants to a 20 cm depth in tropical alley crops was 35% (18-yr) and 24% (9-yr), with similar values (23%) in the temperate system. These results suggest that the rate of SOC turnover in tropical soils (14 yrs) is greater than that of temperate soils (45 years).



Canada, Costa Rica, agroforestry systems, carbon inputs, sustainable agriculture