Browsing by Author "Abekoe, M."

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The combined effect of termite bioturbation and water erosion on soil nutrient stocks along a tropical forest catena in Ghana
(Catena, 2019-03) Kristensen, J.A.; Boëtius, S.H.; Abekoe, M.; Awadzi, T.W.; Breuning-Madsen, H.
In the tropical moist semi-deciduous forests of West Africa, soil catenas with extremely gravel-rich soil horizons at the summits and upper slopes and largely gravel-free profiles at the lower slope are common. Previous investigations have suggested that these gravel layers are the result of macro-invertebrates mining of fine-grained soil material from the subsoil leaving behind the gravel, to build galleries at the surface subsequently exposing it to water erosion transport downslope. We examined the indirect effect of this process on the distribution along a soil catena of crucial base cations (Ca2+, Mg2+, K+) and plant available phosphorous (P), which is often growth-limiting in these tropical ecosystems. We found that the export of fine-grained soil material at the top of the catena reduces the soil stocks (to 1 m) of these elements by up to 60%, while the soil fertility downslope did not change significantly. This important long-term (100–1000 yr scale) reduction in soil fertility at the top of slopes resulting from bioturbation and water erosion is overlooked in contemporary literature, which primarily focus on the beneficial impact termites and ants have on ecosystem functioning in more level savannah landscapes. As the type of catena studied is widespread across tropical environments, this effect is likely ecologically substantial. Future research should aim at understanding such long-term consequences of bioturbation on landscape ecology as well as soil heterogeneity and fertility, so we do not overlook potential negative ecosystem effects.
Effect of different fertilization and irrigation methods on nitrogen uptake, intercepted radiation and yield of okra (Abelmoschus esculentum L.) grown in the Keta Sand Spit of Southeast Ghana
(Agricultural Water Management, 2015-01) Oppong Danso, E.; Abenney-Mickson, S.; Sabi, E.B.; Plauborg, F.; Abekoe, M.; Kugblenu, Y.O.; Jensen, C.R.; Andersen, M.N.
Three seasons' experiments were conducted in the Keta Sand Spit to test if current use of sprinkler irrigation and animal manure can be substituted by water saving drip fertigation with reduced P supply to okra. The treatments compared were: (i) irrigation by sprinkler, fertilized with manure spread, (ii) irrigation by sprinkler, fertilized with localized manure, (iii) irrigation by drip, fertilized with localized manure, (iv) irrigation by drip, fertigated with N-K chemical fertilizers (twice during the crop season in the first experiment, weekly in the second and third experiment). Nitrogen uptake, crop interception of solar radiation, yield and water productivity were compared among treatments. The crop did not respond well when fertigation was done only twice, probably due to N-leaching. However, in the second and third experiments, when fertigation was done weekly for eight weeks, the yield of drip fertigated okra was as high as or better than sprinkler irrigated okra with manure spread on the soil, sprinkler and drip with localized manure. In the second experiment, though nitrogen applied was the same (89kgNha-1), for all treatments, the highest N uptake, intercepted radiation and water productivity were obtained under drip fertigated treatment and these parameters were significantly (P≤0.05) higher than the other treatments. Under sprinkler irrigation, yield was higher with localized manure compared to manure evenly spread on the soil, even though the difference was not significant during the last season. The economic optimal crop N-uptake was estimated to be 125kgha-1 independent of season and adequate N-supply seemed especially important for ensuring sufficient light interception during the fruiting stage of okra. Drip irrigation treatments saved almost 30% of water compared to sprinkler irrigation. Therefore, drip irrigation with frequent fertigation allow reduced P-load and more efficient use of nitrogen, water and radiation than with sprinkler irrigation. © 2014 Elsevier B.V.
Land tenure and differential soil fertility management practices among native and migrant farmers in Wenchi, Ghana: Implications for interdisciplinary action research
(NJAS - Wageningen Journal of Life Sciences, 2004-09) Adjei-Nsiah, S.; Leeuwis, C.; Giller, K.E.; Sakyi-Dawson, O.; Cobbina, J.; Kuyper, T.W.; Abekoe, M.; Van Der Werf, W.
In the past, farmers in the forest-savannah transitional agro-ecological zone of Ghana relied on the bush fallow system for maintaining the productivity of their farmland. However, in recent years population growth-induced pressure on land has increased and farmers have developed various other strategies for improving the productivity of their farmlands. Such strategies have been identified in the context of an interdisciplinary action research project and include rotations with cassava (Manihot esculents), pigeon pea (Cajanus cajan) and cowpea (Vigna unguiculata). Using a social science model for understanding technical farming practices, this article explains the differential adoption of these locally developed soil fertility management strategies. It transpires that native and migrant communities are captured in a social dilemma situation, which has negative consequences for soil fertility in that promising innovations are not utilized optimally. Based on this research experience, this article concludes with a discussion of the implications for co-operation between natural and social scientists in the context of interactive action research. It is argued, amongst other things, that the essence of such co-operation lies in the critical questioning and influencing of each other's key assumptions and disciplinary research agendas.