Submitted to: Proceedings of the International Cocoa Producer's Conference
Publication Type: Proceedings
Publication Acceptance Date: 5/25/2009
Publication Date: 11/16/2010
Citation: Arevalo-Gardini, E., Baligar, V.C., Manuel, C.S., Alegree, J.C. 2010. Soil Biological Parameters Influenced By Cocoa Management Systems. Proceedings of the International Cocoa Producer's Conference. 303-309. Interpretive Summary:
Technical Abstract: Cropping systems have a profound influence on the soil micro-fauna and they are responsible for nutrient cycling, and add stability to the soil. At Tarapoto, Peru, two field experiments were established on acidic medium fertility Alfisol to assess the influence of management systems on cacao rhizosphere biological parameters (fungus, nematodes and bacteria). In the first experiment, 60 cacao genotypes were established in a traditional cacao planting system (TMS) and in a new agroforestry based cacao planting system (AFS). In the second experiment cacao was grown with five cover crops (Calopogonium, Centrocema, Calisia, Arachis, Canavalia) and designated as CCMS. The soil samples of cacao rhizosphere were collected to 0 – 20 cm of depth during the start (2004) and at the end of 2007. Mycological analysis by serial dilution and invert plate technique were done to obtain different fungus genera. Barnett, Barron, Ellis and Watanabe keys were used for identification. Serial dilution and growth in Nutritive Agar techniques were used to differentiate aerobic and anaerobic bacteria. Extraction by sieving and decantation of the modified Cobb method were used for parasitic and non-parasitic nematode identification. The Shannon index was used to register all the biological parameters of species richness. In AFS the fungus richness had 20 genera, with a population of 4.78E+05 cfu gs-1 and a Shannon index of 2.64. In this population, 20% were pathogen and pathogen-saprophytic; 40% had the potential biocontrol and 40% were saprophytic. Whereas in TS, the fungus richness was 22 genera with a population of 5.98E+05 cfu gs-1 and a Shannon index of 2.74. In this system 28% were pathogen and pathogen-saprophytic, the potential biocontrol was 39% and 33% were saprophytic. In CCMS the fungus richness was 9 genera with population of 4.28x104 cfu gs-1 and the Shannon index was 2.13. The frequency of pathogen-saprophytic was 23%; the potential biocontrol was 33%, the saprophytic were 44%, and no pathogenic genera were recorded. In AFS the nematode richness was 18 genera with 868 indiv.100ccs-1 and a Shannon index of 2.12. From this population 51% were parasitic and 49% were non parasitic. In TMS the richness was 13 genera, 1170 indiv.100ccs-1 and with a Shannon index of 1.49; and 72% pertained to no parasitic nematodes. In CCMS the richness was 15 genera, with a population of 2113 indiv.100ccs-1 and Shannon index of 1.74. In this system, 58% accounted for non-parasitic nematodes. The population of bacteria was larger in CCMS, with a population of 1.36E+08 cfu gs-1 followed by AFS with 8.60E+07 cfu.gs-1, and TMS of 7.67E+07 cfu gs-1 population. In all these systems the population of anaerobic bacteria was higher than that of aerobic. The results obtained show that the nature of management has profound effects on rhizosphere biology. A high Shannon index observed in AFS is evidence that this system has positive effects on population dynamics and species richness. And, also, during the initial years of establishment; TMS have favorable effects on the diversity of the soil´s biological parameters.