Browsing by Author "Abekoe, M.K."
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Item Acidity and Aluminum Speciation in Biochar Amended Tropical Soils(Taylor & Francis Group, 2022) Eduah, J.O.; Nartey, E.K.; Abekoe, M.K.; Asomaning, S.K.; Essibu, J.K.; Henriksen, S.W.Soil acidification in the tropics has become a more pressing issue due to its associated aluminum (Al) phytotoxicity. The chemical reactive nature of biochar can alter Al speciation in soils. The study assessed the chemical properties and Al speciation in a Ultisol and an Oxisol amended with corn cob (CC) and rice husk (RH) biochars charred at 300, 450 and 650°C in an incubation study for 120 d. pH was determined periodically while organic carbon (OC), cation exchange capacity (CEC), exchangeable base cations, exchangeable acidity, and exchangeable Al3+ were measured at the end of the incubation period. Dissolved organic carbon (DOC) and pH were also determined in soil solution from each treatment. Throughout the incubation period CC and RH biochars significantly increased soil pH, with CC biochar showing a greater effect. Similar effects were also observed for OC, CEC, and exchangeable base cations (Ca2+, Mg2+ and K+). Soil exchangeable Al3+ and exchangeable acidity, soluble Al and Al3+ activity in soil solution decreased significantly upon biochar application; it was more significant at the 650°C. Biochars at 300–450°C exhibited a more notable increase in soil DOC. At pH ≤ 5.8, Al-DOC and free Al3+ dominated in soil solution while at pH > 5.8, Al species was mainly Al-OH ions (i.e. Al(OH)2+, Al(OH)2 +, Al(OH)3, and Al(OH)4−). Biochars at 300–450°C promoted the large formation of Al-DOC while Al-OH ions dominated in 650°C-biochar treatments. Biochar can be used to ameliorate Al phytotoxicity in tropical acid soils, particularly at 300–450°C.Item Assessing the effect of seedling age and time of urea supergranule application on rice growth, yield and nitrogen use efficiency(Open Access Volume 27, Issue 1, 2019, Pages 78-94, 2019-09-27) Abekoe, M.K.; Koudjega, K.; Ablede, K.A.; Lawson, I.Y.D.; Owusu-Bennoah, E.Nitrogen is the most limiting nutrient in tropical soils and nitrogen fertilizer application to rice is subject to losses. Good synchrony of nitrogen availability to crop’s need is a strategy to reduce losses and improve efficiency. A pot experiment was conducted to assess the effect of seedling age and time of urea supergranule application on rice growth, yield and nitrogen use efficiency. The experiment consisted of 10, 14, 21 and 28-day old seedlings and urea supergranule applied at 0, 7, 14 and 21 days after transplanting with a check treatment without nitrogen application. Results indicated significant effect of seedling age on growth, yield and nitrogen use efficiency. Highest grain yield, nitrogen uptake, agronomic use efficiency of nitrogen and nitrogen recovery efficiency were obtained with 10 and 14-day old seedlings, while the lowest values were observed for 28-day old seedlings. Urea supergranule applied at 7 or 14 days after transplanting gave the highest rice growth parameters while the lowest performances were obtained with urea supergranule applied at 0 and 21 days after transplanting. The interactive effect showed better growth, yield and nitrogen use efficiency of rice when urea supergranule was applied at 7 or 14 days after transplanting seedlings of 10 and 14-day old. The results suggested that even though application of urea supergranule at 7 and 14 days after transplanting increased rice yield over 0 and 21 days after transplanting, for the aged seedlings of 21 and 28-day old, the variation of urea supergranule application time could not compensate for the decrease of yield due to old seedlings transplanting.Item Determination of activity concentration levels of 238U, 232Th, and 40K in drinking water in a gold mine in Ghana(Health Physics, 2010-08) Awudu, A.R.; Darko, E.O.; Schandorf, C.; Hayford, E.K.; Abekoe, M.K.; Ofori-Danson, P.K.The study of the activity concentration levels of uranium, thorium and potassium in drinking water from different locations in a gold mine in the Ashanti Region of Ghana was conducted using gamma spectrometry. The mean outdoor absorbed gamma dose rates at 1 m from the water were 0.524 nGy h-1, 0.422 nGy h-1, and 0.252 nGy h-1 for groundwater, surface water, and treated water, respectively. The results obtained for the activity concentration levels of U and Th are found to be within the maximum acceptable concentration levels of 3.0 Bq L-1 and 0.6 Bq L-1, respectively, recommended by the World Health Organization. The overall mean outdoor gamma dose rate is 0.41 nGy h-1 and the corresponding outdoor annual effective dose obtained for adult members of the public for drinking water from the mines is 3.58 μSv y-1. This value is found to be within the 10.0 μSv per annum (0.01 mSv per annum) for public exposure control set by the World Health Organization. Therefore, the mining activities on drinking water studied did not show any significant radiological health implications on the public. Copyright © by the Health Physics Society.Item Downscaled climate change projections for Wa District in the Savanna zone of Ghana(Journal of Disaster Research, 2014-07) Tachie-Obeng, E.; Hewitson, B.; Gyasi, E.A.; Abekoe, M.K.; Owusu, G.The possibility of future climate change in Ghana has received much attention due to repeated droughts and floods over the last decades. The savanna zone which is described as the food basket of Ghana is highly susceptible to climate change impact. Scenarios from 20- year time slices of the near future - 2046-2065 - and the far future - 2081-2100 - climate change meant to help guide policy remain a challenge. Empirical downscaling performed at the local-scale of Wa District in the savanna zone of Ghana under the IPCC A2 SRES emissions scenario showed evidence of probable climate change with mean annual temperatures expected to increase over an estimated range of 1.5°C to 2.3°C in the near future, with number of cool nights becoming less frequent, especially during the Harmattan1 period. The dry season is expected to be warmer than the wet season, with high inter-annual variations projected in both maximum (Tmax) and minimum (Tmin) temperatures. Given an average of 1 day of Tmax > 40°C per month in the control period of 1961-2000, the number of hot days is expected to increase to 12 by 2046-2065. An increase in total rainfall is projected with possible shifts in distribution toward the end of the year, with a slight increase in rainfall during the dry season and an increase of rainfall at the onset and toward the end of the wet season. However, a decrease in June rainfall is projected in the wet season. The objective of this paper is to improve the understanding of future climate as a guide to local level medium-term development plans of effective adaptation options for Wa district in the savanna zone of Ghana.Item Dynamics of Soil Carbon Sequestration under Oil Palm Plantations of Different Ages(University of Ghana, 2013-07) Wisdom, B.S.; Owusu-Bennoah, E.; Abekoe, M.K.It has been estimated that globally a lot of forest is lost in the tropics annually to agriculture. The removal of the forest cover has been cited as one of the main contributors of greenhouse gases. Tree plantations are advocated as carbon (C) sink, however, little is known about rates of C turnover and sequestration into soil organic matter under tropical tree plantations particularly oil palm. One of the commonest management practices adopted by farmers on oil palm plantations involves the prunning of the palm branches and heaping them in between the palm trees in the rows. The spaces or the alleys between the palm trees contained no heaped branch residues. So far very few studies have been conducted to assess the contributions of pruned branches heaped at the different locations under the palm plantations to the fertility status of the soil. The objective of this research was to assess the dynamics of soil C sequestration under oil palm (Elaeis guineensis) plantations at different ages in a semi deciduous forest zone of Ghana. A diagnostic field study was carried out to identify oil palm plantations at different ages occurring within the Kwaebibirem District, Ghana. The oil palm plantations were categorised into five age groups (0-5, 5-10, 10-15, 15-20 and 20-25 years). A forest reserve which had not been cultivated for more than 50 years served as a control. All the cultivated farms and the control plot were located at the valley bottom slope on Oda soil series (Aeric Endoaquent). Soil samples were collected under the heaped branches and from the spaces between the palm trees at a depth of 0- 10 and 10-20 cm respectively. The control soil from uncultivated plot was also taken at the same depth. The soil samples were collected for bulk density (BD) and organic C determinations. Carbon stocks were calculated using measured C content and the corresponding soil bulk densities. The presence of the residue resulted in lower BD values under heaps than those under alleys with age irrespective of the depth. The OC in the soil decreased with cultivation but was drastic after 5 years of plantation establishment up to age 20 years in both layers under heaps with losses accounting for between 13-45% of the control. In the alleys the OC losses were greater with age in both depths with the lower layer having OC deficit of 57%. The conversion of the forest into the oil palm plantation led to a dramatic loss in soil C stocks of around 45% in the top 10cm irrespective of heap or alley location. In the 10-20cm layer loss was 50-60% with lower decline under residue heaps. Under heaps significant improvements in the C stocks in the top layer is discernible after 20 years but not in the alleys. The carbon saturation deficit followed a similar trend as the C stocks. The conclusion from this study is that oil palm plantations have the ability to sequester carbon over a period of time when palm fronds are added to the soil.Item Effect of Phosphorus Sources on Nodulation and Dry Matter Yield of Pigeonpea(University of Ghana, 2014-03) Yanquoi, H.; Abekoe, M.K.; University of Ghana, College of Basic and Applied Sciences, School of Agriculture, Department of Soil SciencePhosphorus (P) is an essential element which has been identified as a major plant nutrient that limits nitrogen (N2) fixation in legumes. Different sources of water soluble P have been used to increase growth, nodulation and N2 fixation in legumes , but there is inadequate information on the effect of phosphate rocks (PRs) on the growth, nodulation, and N2 fixation of pigeonpea. In this study, Togo rock phosphate (TRP), and water soluble triple superphosphate (TSP) were used to test the effect of P application on dry matter yield and nodulation of pigeonpea. The objectives of the study were to (i) compare Togo rock phosphate with Triple super phosphate with respect to: dry matter yield and nodulation of pigeonpea using two soil series (Toje and Bumbi), (ii) assess the rate of phosphorus application for maximum dry matter yield and nodulation in pigeonpea and (iii) compare the agronomic effectiveness of the two P sources in a green house experiment. The study was carried out in pots with phosphorus application rates of 0, 30, 60, 90, 120, and 150 kg P/ha and pigeonpea was used as a test crop. The plants were grown and harvested 6 weeks after planting. The shoots were analyzed for dry matter yield and phosphorus uptake and root nodule numbers were counted and weighed. The relative agronomic effectiveness (RAE) of the Togo rock phosphate was calculated using the dry matter yield and P uptake at 120 kg P/ha application rate. The results of the pot experiment showed that the dry matter yield (DMY) of the pigeonpea crop increased consistently from 0-P kg/ha to 120 kg P/ha and decreased at 150 kg P/ha in both soils. The DMY, nodule numbers and weight in the Toje soil series were significantly higher than in the Bumbi soil despite the relatively higher fertility status of the Bumbi soil series (p < 0.05). This suggests that soil fertility is not the only parameter to be considered for growth and development of crops. For soil productivity, both the chemical and the physical properties are equally important since they both contribute to the root development and exploration for nutrients and water in the soil. Dry matter yield, nodule numbers and weight of the pigeonpea obtained in the TSP treatments were significantly higher than those of the Togo rock phosphate treatments. The agronomic effectiveness of the TRP in the two soils showed that in the Toje soil series, the RAE was 27 % and in the Bumbi soil series, it was 18 % that of the TSP. This could be attributed to the fact that the Togo rock phosphate did not dissolve adequately well to supply the needed P to the pigeonpea during the six weeks growing period.Item Enhancing the agronomic effectiveness of natural phosphate rock with poultry manure: A way forward to sustainable crop production(Nutrient Cycling in Agroecosystems, 2007-08) Agyin-Birikorang, S.; Abekoe, M.K.; Oladeji, O.O.Phosphorus inputs are required in highly weathered tropical soils for sustainable crop production. However, high cost and limited access to mineral P fertilizers limit their use by resource-poor farmers in West Africa. Direct application of finely ground phosphate rock (PR) is a promising alternative but low solubility of PR hampers its use. Co-application of PR with manure could be a low cost means of improving the solubility of natural PR and improve their agronomic effectiveness. Our objective was to quantitatively estimate the enhancement effect of poultry manure on P availability from low reactive PR (Togo phosphate rock) applied to highly weathered soils. We utilized two highly weathered soils from Ghana and Brazil for this greenhouse study. Using 32P isotopic tracers, the agronomic effectiveness of poultry-manure-amended Togo rock phosphate (TPR) was compared with partially acidulated Togo rock phosphate (PAPR) and triple superphosphate (TSP). Four rates of poultry manure: 0, low (30 mg P kg-1 soil), high (60 mg P kg-1 soil) and very high (120 mg P kg-1 soil) were, respectively, added to a constant amendment (60 mg P kg-1 soil) of the P sources and applied to each pot of 4 kg soil. A Randomized Complete Block Design was used for the greenhouse experiment and Maize (Zea mays L.) was used as a test crop. The plants were grown for 42 days after which the above ground biomass was harvested for analysis. Without poultry manure addition, the agronomic effectiveness, represented by the relative agronomic effectiveness (RAE) and proportion of P derived from fertilizer (% Pdff) was in the order TSP > PAPR > TPR = control (P0). In the presence of low rate poultry manure addition, the agronomic effectiveness followed the order TSP > PAPR = PR > P0. However, at the high and very high rates of poultry manure addition, no significant differences in agronomic effectiveness were observed among the P sources, suggesting that at this rate of poultry manure addition, PR was equally as effective as TSP. The study showed that direct application of PR co-applied with poultry manure at a 1:1 P ratio will be a viable option for P replenishment. Thus a combination of PR and poultry manure could be a cost-effective means of ensuring sustainable agricultural production in P-deficient, highly weathered tropical soils. © 2007 Springer Science+Business Media B.V.Item Evaluating sustainable and profitable cropping sequences with cassava and four legume crops: Effects on soil fertility and maize yields in the forest/savannah transitional agro-ecological zone of Ghana(Field Crops Research (103): 87-97, 2007) Adjei-Nsiah, S.; Kuyper, T.W.; Leeuwis, C.; Abekoe, M.K.; Giller, K.E.Item Farmers’ agronomic and social evaluation of productivity, yield and N2-fixation in different cowpea varieties and their subsequent residual N effects on a succeeding maize crop(Nutrient Cycling in Agro-ecosystem (80): 189-109, 2008) Adjei-Nsiah, S.; Kuyper, T.W.; Leeuwis, C.; Abekoe, M.K.; Cobbinah, J.; Sakyi-Dawson, O.; Giller, K.E.Item Heat tolerance in field grown tomatoes (Lycopersicon esculentum Mill.) under semi-arid conditions of west Africa(Acta Horticulturae, 2013-01) Kugblenu, Y.O.; Danso, E.O.; Ofori, K.; Andersen, M.N.; Abenney-Mickson, S.; Sabi, E.B.; Plauborg, F.L.; Abekoe, M.K.; Jørgensen, S.T.; Jensen, C.R.; Ofosu-Anim, J.One major reason for extremely low production of tomato in Ghana is that the length of the growing season last only for a few months due to the high temperature influx during the remaining months. The temperatures recorded during these months are above the optimum for tomato flowering and fruiting and this consequently affects yield. To solve this problem a number management practices may be undertaken such has growing heat tolerant tomato varieties or providing shade to mitigate the devastating effect of high temperatures. Therefore the present study was conducted outside the normal growing season from June to October, which has a mean temperature of 23°C. Heat tolerant tomato cultivars were grown from April to July with a mean temperature of 25°C to evaluate their performance under these conditions and to assess the effect of shading on the production of one of the genotypes. Fruiting percentage was significantly lower in exotic hybrids compared to a local variety. Different genotypes showed no differences in the production of viable pollen. Shading decreased final shoot and root biomass by 67 and 47%, respectively, whiles fruit yield was not affected. Also among cultivars yields were similar.Item Impact of farm management practices and agricultural land use on soil organic carbon storage potential in the Savannah Ecological zone of Northern Ghana(Journal of Disaster Research, 2014-08) Boakye-Danquah, J.; Antwi, E.K.; Saito, O.; Abekoe, M.K.; Takeuchi, K.In recent times, there has been increasing interest in the importance of agricultural soils as global carbon sinks, and the opportunity of enhancing the resilience of degraded agroecosystems - particularly in savannah regions of the world. However, this opportunity is largely a function of land use and/or land management choices, which differ between and within regions. In the present study, we investigated the role of agriculture land use and farm management practices on soil organic carbon (SOC) storage in the savannah regions of northern Ghana. We evaluated selected land use types by using an integrated approach, involving on-farm interviews, community transect walks, land use monitoring, and soil sampling. Our results indicated that, at the landscape level, community land use and resource needs are important determinants of SOC storage in farmlands. We determined low SOC accumulation across the investigated landscape; however, the relatively high SOC stock in protected lands compared with croplands implies the potential for increasing SOC build-up by using recommended management practices. Low incomes, constraints to fertilizer use, low biomass availability, and reductions in fallow periods remain as barriers to SOC buildup. In this context, global soil carbon storage potential and smallholder food production systems will benefit from an ecosystembased adaptation strategy that prioritizes building a portfolio of carbon stores at the landscape level.Item The Interactive Effect of Residue Quality, Quantity, Soil Texture and N Management on Maize Crop Yield in Ghana(Improving the Profitability, Sustainability and Efficiency of Nutrients Through Site Specific Fertilizer Recommendations in West Africa Agro-Ecosystems, 2018-04) Yeboah, E.; Abekoe, M.K.; Dowuona, G.N.N.; Vanlauwe, B.; Sohi, S.P.; Six, J.W.Food insecurity and declining soil fertility across much of sub-Saharan Africa in recent decades have led to pursuit of alternative nutrient management strategies for both improving crop yields and the restoration of degraded soils. In this respect, a 3-year field based studies involving two sites (Ayuom and Kwadaso) of contrasting soils (Suko and Nzima series) in the semi-deciduous forest zone of Ghana was initiated in year 2003. The treatments involved 5 organic resources of different qualities (in terms of N, lignin and polyphenol) with and without inorganic N application. The organic resources were applied at two application rates; 1.2 t C ha−l year.−l and 4 t C ha−l year.−l in the major season and the residual effect evaluated in the ensuing minor season. Cumulative maize grain yield (3 years) at Ayuom on the Suko series for the major season showed that 1.2 t C ha−lL. leucocephala+120 kg N ha−l proved to be the most effective treatment with yield of almost 18,000 kg ha−l. At Kwadaso on the Nzima series however, 4 t C ha−l Cattle manure+120 kg N ha−l for the minor season was the most effective. At both sites, major season grain yields were generally higher than minor season. Furthermore, between cropping seasons, maize yields were superior on the Suko series than the Nzima series. To improve food security in the semi-deciduous forest zone of Ghana, soil nutrient management to restore soil fertility should take into consideration: soil type, cropping season, organic resource quality and quantity as well as their interaction with inorganic N.Item Long-term cropping effect on phosphorus fractions in an Ultisol of the humid forest zone in West Africa(Communications in Soil Science and Plant Analysis, 2003-03) Abekoe, M.K.; Sahrawat, K.The nature of phosphorus (P) pools in soils after application of P fertilizers should be considered when designing management practices to raise P fertility. Five rates of P: 0(P0), 45(P45), 90(P90), 135(P135) and 180(P180) kg ha-1 in the form of triple superphosphate (TSP) were applied once in 1993 on a Typic Paleudult at Man in Côte d'Iviore and the soil was cropped successively for five years (i.e., up to 1998) with four upland rice cultivators. At the end of the cropping season in 1998, soil samples were collected from the various P treated plots and the following P fractions were analyzed: resin-P, NaHCO3-Pi, NaOH-Pi, HCl-P residual P and organic P. The P fractions were compared with those of stored soil samples collected in the field before the initiation of the experiment in 1993. Five years of cropping the soil reduced labile Pi (resin-P + NaHCO3-Pi) from 10.8 mg P kg-1 in the uncultivated soil to 7.62mg P kg-1 in the control (P0) and to 9.71 mg kg-1 in the P45 treatment. Labile Pi in P90 was the same (10.7 mg P kg-1) as in the uncultivated soil but in the P135 and P180 soils, labile Pi increased by 1.3 and 2.7 mg P kg-1 above that of the uncultivated one. The NaOH-Pi and residual P fractions of lower availability increased with increasing rates of P application. The results suggested that on the Ultisol studied, P applied once to a field, cropped successively over a period of time was not an adequate management option. Frequent P application at low rates at each cropping season is suggested and merits investigation on the Ultisol studied.Item Mapping fertilizer recommendations for cocoa Production in Ghana using soil siagnostic and GIS tools(West African Journal of Applied Ecology, 2009-09) Snoeck, D.; Afrifa, A.A.; Ofori-Frimpong, K.; Boateng, E.; Abekoe, M.K.The intensely weathered nature of soils used for cocoa production in Ghana, and the long history of nutrient depletion due to the absence of fertilization in this farming system have resulted in increased incidence of soil nutrient deficiencies in cocoa farms. The paper discusses the use of a soil diagnostic model combined with geographic information systems (GIS) to convert the current blanket fertilizer recommendations (0 N - 165 P2O5 -200 K2O kg ha-1) into a more effective recommendation that accounts for local land resources and the actual nutrient requirements of cocoa trees. A digital map of cocoa nutrient requirements was created based on climatic and soil groups/associations data. The results showed that about 95% of the areas suitable for cocoa production are developed on only seven soil groups and four sub-groups (FAO classification). As inputs, 201 soil chemical analytic data were linked to land units to compute cocoa fertilizer formulae and doses. The number of fertilizer formulae was reduced to 32 using a fuzzy classification. Six fertilizer formulae would be sufficient to cover fertilizer recommendations for 52% of the cocoa growing areas, while 16 fertilizer formulae will cover 90% of the cocoa area. The current blanket fertilizer formula is only suitable for 6% of the cocoa growing areas in Ghana. In western Ghana, where rainfall is over 1800 mm, the climatic influence is predominant and high leaching of soils is probably responsible for greater needs for P, than for K, Ca, and Mg. In eastern Ghana, where soils have high exchangeable cation levels and base saturation, soil diagnostic method suggested application of N fertilizers. This integrated method could provide precision agriculture techniques for cocoa farmers in Ghana, and beyond, in order to sustain yields on cocoa farms.Item Mechanism of orthophosphate (PO4-P) adsorption onto different biochars(Environmental Technology & Innovation, 2019-12-04) Eduah, J.O.; Nartey, E.K.; Abekoe, M.K.; Henriksen, S.W.; Andersen, M.N.The adsorption mechanisms of phosphate (PO4-P) onto cocoa pod husk (CP), corn cob (CC), rice husk (RH) and palm kernel shell (PK) biochar pyrolyzed at 300 ◦C and 650 ◦C were investigated. A series of batch experiments were undertaken to assess the effects of contact time and pH. Results show that PO4-P adsorption equilibria for the biochar types was within 6–15 h, being rapid in the 300 ◦C-biochar types. The equilibrium pH for maximum PO4-P adsorption varied among biochar types, ranging from of 2.6 to 4.8 and increasing with decreasing PO4-P adsorption. Pseudo-secondorder and Elovich models explained the adsorption data well indicating a chemisorption process on heterogeneous biochar surface. PO4-P adsorption was controlled initially by intraparticle diffusion and subsequently by chemisorption. Per the properties of the biochars (FTIR and elemental composition) and pH (equilibrium pH and ΔpH), PO4–P was adsorbed through electrostatic attraction, surface precipitation and ligand exchange, and the relative importance of these processes differed among the biochar types. Biochar types (PK300, PK650, CP300, CP650, RH650 and CC650) that adsorbed PO4-P through surface precipitation and ligand exchange reactions can be used to remove PO4-P from wastewater since PO4-P is strongly adsorbed, controlling PO4-P enrichment of water bodies.Item Nonlinear sorption of phosphorus onto plant biomass-derived biochars at different pyrolysis temperatures(Environmental Technology & Innovation, 2020-04-18) Eduah, J.O.; Henriksen, S.W.; Nartey, E.K.; Abekoe, M.K.; Andersen, M.N.Aside the characterization of feedstocks and biochars (BCs), the nonlinear sorption of phosphorus (P) onto corn cob (CC), rice husk (RH), cocoa pod husk (CP) and palm kernel shell (PK) BCs charred at 300, 450 and 650 ◦ C were investigated using series of batch experiments. Conversion of feedstock to BC resulted in a higher pH, C content, ash, fixed C, surface area (SA) and lower volatile matter, moisture, H, N, O and S contents. Increasing pyrolysis temperature proportionally decreased the polarity (O/C, O+N/C, and O+ N+ S/C), volatile matter, moisture content, readily labile organic C and potentially unstable C vis-à-vis an increased in C content, fixed C, stable C and aromaticity (H/C). The nonlinearity index (n) as well as P sorption capacity (KF ) increased with temperature and were highly dependent on BC properties. Significant linear relationships were observed between P sorption parameters (n and KF ) and O content, polarity, aromaticity, fixed C, stable C, readily labile organic C and SA. The low polarity and high aromaticity and SA resulted in the high nonlinear sorption of P at 650 ◦ C. Findings of this study provides insight into P sorption behaviour, thereby serving as a theoretical basis for biochar application either agronomically or environmentally.Item Phosphate retention and extractability in soils of the humid zone in West Africa(Geoderma, 2001-07) Abekoe, M.K.; Sahrawat, K.L.Phosphate adsorption and desorption studies provide insight for developing P management strategies. Very few studies have concentrated on P desorption which provides information on the reversibility of adsorbed P. Phosphate adsorption and desorption studies were carried out on seven rice-growing soils from three countries in West Africa, with the objective of relating these processes to P management strategies for the soils. The standard P requirement (SPR) of soils, defined as the amount of P to be added to attain an equilibrium solution concentration of 0.2 mg P 1-1, varied from 42 to 175 mg P kg-1. Out of the seven soils, four required low amounts and the other three needed relatively higher P applications. The extractability of the adsorbed P in different extractants was: 0.01 M KCl 32-78%, Olsen P 21-112%, and Bray 1 P 15-40%. Differences in the amounts of P desorbed by the soils suggested that the critical P levels needed for P management must be different. Management options to increase P availability in the soils are suggested. © 2001 Elsevier Science B.V.Item Phosphorus retention and availability in three contrasting soils amended with rice husk and corn cob biochar at varying pyrolysis temperatures(Geoderma, 2019-05) Eduah, J.O.; Nartey, E.K.; Abekoe, M.K.; Breuning-Madsen, H.; Andersen, M.N.The reactive nature of phosphorus (P) leads to the formation of insoluble Fe, Al and Ca phosphates in highly weathered tropical soils, thus reducing P availability for plant uptake. Biochar with its heterogeneous surface properties as influenced by feedstock and pyrolysis temperature can affect P retention and availability in tropical soils. In the present study, incubation studies were conducted for 90 days to investigate the effect of corn cob and rice husk biochar on P sorption and desorption in two acid (Typic Plinthustult-A & Plinthic Acrudox-B) and one neutral soil (Quartzipsamment-C). The biochars were pyrolyzed at varying temperatures (300 °C, 450 °C and 650 °C) and applied at a rate of 1% (w/w) to the soils. Phosphorus sorption data were fitted to Langmuir and Freundlich models. Phosphorus desorption was done on the residual samples that received initial P concentrations of 21.5 mg L−1, 43.0 mg L−1 and 86.0 mg L−1 solution using 10 mM KCl. The P sorption capacity of the two acid soils i.e. A (395 mg kg−1) and B (296 mg kg−1) were more than two fold that of the neutral soil (C) (105 mg kg−1). Addition of the biochar types to soil A raised the equilibrium P concentration in solution at decreasing pyrolysis temperature. Similar trend was observed in soil B with the exception of corn cob and rice husk biochar at 650 °C which increased the soil's (B) P sorption capacity. In soil C, both biochar types increased P sorption capacity with increasing pyrolysis temperatures. Phosphorus desorbability increased with increasing initial P concentrations in the three soils. Generally, P desorbability increased in the acid soils but decreased in the neutral soil upon biochar amendment. Decreases in P adsorption and consequently increases in P desorption were more pronounced when the 300 °C biochar types were amended with the soils. The study thus showed that biochar pyrolyzed at 300–450 °C could be used to reduce P sorption and increase P bioavailability especially in acid soils. The addition of biochar to neutral or alkaline soils might increase P retention possibly in the short-term, reducing P bioavailability.Item Phosphorus sorption capacity in relation to soil properties in profiles of sandy soils of the Keta sandspit in Ghana(West African Journal of Applied Ecology, 2018-01) Asomaning, S.K.; Abekoe, M.K.; Dowuona, G.N.N.The sandy soils of Anloga in the Volta region form part of the Keta basin. The soils are infertile and of low productivity but are intensively cultivated for vegetables such as shallot (Allium cepa). Farmers have augmented the fertility of the soils by adding cow dung and poultry manure for the past seventy years. To study the P dynamics in the soils, three profiles were dug on cultivated (F) and two on uncultivated (U) fields to study P accumulation and sorption after decades of cultivation. The results showed that total P content was 533 mg P kg-¹ at the depth of 50 cm and below in the F-profiles compared to 416 mg P kg-¹ of similar depth of the uncultivated soils, suggesting some movement of P from the surface soil into the subsoil. The maximum P sorption capacity of the U soils was low (92 6 mg kg-¹) but higher than those of the F soils (58.8 mg P kg-¹). Multiple regression analyses showed that pH and Ca were the two major determinants of P sorption in the soils. The degree of P saturation (DPS) of the surface soils of the cultivated soils was higher than the average critical value of 25% DPS of an arable land but in the lower depths of the cultivated soils, the DPS decreased tremendously below the critical level of 25% which meant that these depths were not saturated well enough to enhance leaching of P to the underground waters.Item Poultry litter and cow dung biochar as P sources for cowpea cultivation in two Ghanaian soils(Frontiers in Agronomy, 2023) Nartey, E.K.; Sulemana, N.; Razak, A.; Adjadeh, T.A.; Akumah, A.M.; Amoatey, C.; Abekoe, M.K.Introduction: The main constraint to cowpea, Vigna unguiculata, production in West Africa is unavailability of applied phosphorus due to ligand exchange with clay minerals and precipitation reactions facilitated by low pH and low organic matter. Materials and methods: To overcome this challenge, cow dung biochar (CB) and poultry litter biochar (PB) were applied as P sources for cowpea cultivation in Plinthustult and Kandiustalf soil in Ghana. The biochar types and triple super phosphate (TSP) were applied to meet the standard phosphorus requirement (SPR) and ½ SPR of the soils. Basal K from KCl was added to the TSP treatment. In addition to a non-amended soil, the treatments were triplicated and arranged in a completely randomized design in a screen house for an efficacy trial using cowpea as the test crop. Moisture content was maintained at 80% field capacity. Results and discussion: Hundred cowpea seed weight was 20.3 g and 19.6 g for the TSP-amended Plinthustult at SPR and ½ SPR, respectively. This increased to 25.1 g and approximately 27 g at SPR and ½ SPR in the CB- and PB-amended Plinthustult, respectively. Hundred seed weight for TSP at both rates was similar in the two soils. The PB-amended Kandiustalf at SPR had seed with a weight of 27.02 g, 1.1 g heavier than the ½ SPR. The CB-amended Kandiustalf at both rates had 100 seeds weighing 25 g. Residual available P was 334.2 mg/kg and 213.2 mg/kg at SPR and ½ SPR, respectively, in the Plinthustult as opposed to a paltry 2.5 mg/kg at SPR in the TSP counterpart. The study recommends for the two biochar types to be applied at ½ SPR.