Department of Soil Science

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Accounting for Weather Variability in Farm Management Resource Allocation in Northern Ghana: An Integrated Modeling Approach
(Sustainability, 2023) Adelesi, O.O.; Kim, Y-UK.; Adiku, S.G.K.; et al.
Smallholder farmers in Northern Ghana face challenges due to weather variability and market volatility, hindering their ability to invest in sustainable intensification options. Modeling can help understand the relationships between productivity, environmental, and economical aspects, but few models have explored the effects of weather variability on crop management and resource allocation. This study introduces an integrated modeling approach to optimize resource allocation for smallholder mixed crop and livestock farming systems in Northern Ghana. The model combines a process-based crop model, farm simulation model, and annual optimization model. Crop model simulations are driven by a large ensemble of weather time series for two scenarios: good and bad weather. The model accounts for the effects of climate risks on farm management decisions, which can help in supporting investments in sustainable intensification practices, thereby bringing smallholder farmers out of poverty traps. The model was simulated for three different farm types represented in the region. The results suggest that farmers could increase their income by allocating more than 80% of their land to cash crops such as rice, groundnut, and soybeans. The optimized cropping patterns have an over 50% probability of increasing farm income, particularly under bad weather scenarios, compared with current cropping systems.
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.
Agro-Industrial Waste Biochar Abated Nitrogen Leaching from Tropical Sandy Soils and Boosted Dry Matter Accumulation in Maize
(Journal of Carbon Research, 2023) Egyir, M.; Lawson, I.Y.D.; Dodor, D.E.; Luyima, D.
This study was conducted to assess the effects of amending tropical sandy soils with biochar derived from agro-industrial wastes on the leaching and utilization of nitrogen (N) by maize. The experiment was conducted in pots in a greenhouse with two sandy soil types and two different biochars. The biochars used in this experiment were preselected in a preliminary column experiment that assessed the N retention capacities of the different biochars and those that exhibited the best retention capacities chosen for experimentation. The biochars evaluated included saw dust, rice husk and corncob pyrolyzed at 500 ◦C and the results from the column leaching experiment showed that sawdust biochar had superior retention capacities for both NO3 − and NH4 + , followed by rice husk biochar. The pot experiment utilized sawdust and rice husk biochars applied at rates of 0, 20 and 40 t/ha to the soil treated with different N sources including cow dung and ammonium sulfate and growing maize on the amendments for two seasons with each season lasting for five weeks. The soils were leached on the 14th and 28th days after planting to determine the amount of leachable N. Biochar amendments reduced the leaching of NO3 −N and NH4 +N with no significant differences observed between biochar types, but between soil types. The abatement of leaching by biochar amendments consequently enhanced N uptake by maize and dry matter production and thus, agro-industrial waste biochar amendment is recommended for reducing leaching in tropical sandy soils.
Agro-Industrial Waste Biochar Abated Nitrogen Leaching from Tropical Sandy Soils and Boosted Dry Matter Accumulation in Maize
(Journal of Carbon Research, 2023) Egyir, M.; Lawson, I.Y.D.; Dodor, D.E.; Luyima, D.
This study was conducted to assess the effects of amending tropical sandy soils with biochar derived from agro-industrial wastes on the leaching and utilization of nitrogen (N) by maize. The experiment was conducted in pots in a greenhouse with two sandy soil types and two different biochars. The biochars used in this experiment were preselected in a preliminary column experiment that assessed the N retention capacities of the different biochars and those that exhibited the best retention capacities chosen for experimentation. The biochars evaluated included saw dust, rice husk and corncob pyrolyzed at 500 ◦C and the results from the column leaching experiment showed that sawdust biochar had superior retention capacities for both NO3 − and NH4 + , followed by rice husk biochar. The pot experiment utilized sawdust and rice husk biochars applied at rates of 0, 20 and 40 t/ha to the soil treated with different N sources including cow dung and ammonium sulfate and growing maize on the amendments for two seasons with each season lasting for five weeks. The soils were leached on the 14th and 28th days after planting to determine the amount of leachable N. Biochar amendments reduced the leaching of NO3 −N and NH4 +N with no significant differences observed between biochar types, but between soil types. The abatement of leaching by biochar amendments consequently enhanced N uptake by maize and dry matter production and thus, agro-industrial waste biochar amendment is recommended for reducing leaching in tropical sandy soils.
Agro-industrial waste biochar abated nitrogen leaching from tropical sandy soils and boosted dry matter accumulation in maize
(Journal of Carbon Research, 2023) Egyir, M.; Lawson, I.Y.D.; Dodor, D.E.; Luyima, D.
This study was conducted to assess the effects of amending tropical sandy soils with biochar derived from agro-industrial wastes on the leaching and utilization of nitrogen (N) by maize. The experiment was conducted in pots in a greenhouse with two sandy soil types and two different biochars. The biochars used in this experiment were preselected in a preliminary column experiment that assessed the N retention capacities of the different biochars and those that exhibited the best retention capacities chosen for experimentation. The biochars evaluated included saw dust, rice husk and corncob pyrolyzed at 500 ◦C and the results from the column leaching experiment showed that sawdust biochar had superior retention capacities for both NO3 − and NH4 + , followed by rice husk biochar. The pot experiment utilized sawdust and rice husk biochars applied at rates of 0, 20 and 40 t/ha to the soil treated with different N sources including cow dung and ammonium sulfate and growing maize on the amendments for two seasons with each season lasting for five weeks. The soils were leached on the 14th and 28th days after planting to determine the amount of leachable N. Biochar amendments reduced the leaching of NO3 −N and NH4 +N with no significant differences observed between biochar types, but between soil types. The abatement of leaching by biochar amendments consequently enhanced N uptake by maize and dry matter production and thus, agro-industrial waste biochar amendment is recommended for reducing leaching in tropical sandy soils.
Ameliorating acid infertile rice soil with organic residue from nitrogen fixing trees
(Nutrient Cycling in Agroecosystems, 2000-06) Baggie, I.; Zapata, F.; Sanginga, N.; Danso, S.K.A.
Residues from two nitrogen fixing trees, Albizia zygia and Gliricidia sepium and one non nitrogen fixing tree Samania dinklagei and their combination with 50% of rice husk, were evaluated for their effect on growth and yield of rice (Oryza sativa) varieties (Rok 10 and Rok 23) grown in an Oxisol collected from a rice paddy in Inland valley swamps of Sierra Leone, West Africa. Ground and dried residues were mixed with soil and labelled with N15 ammonium sulfate (9.855% atom excess) at a rate of 10 mg N kg-1 soil. The 32P isotopic exchange method was used to determine the effect of organic residue incorporation on the bioavailable soil P status at five levels of P application. Albizia zygia and G. sepium had higher quality leaf litter (with relatively lower C/N, lignin/N and cellulose/N ratios) whereas Semania dinklagei and rice husk had high carbon. lignin and polyphenolic contents. Application of organic residue had positive effects on the soil available P status at varying degrees. Higher adsorption capacity, kinetic value and mean solution time of phosphates in solution were obtained with the A. zygia, and G. sepium residues. These values were lower with rice husk and S. dinklagei. Gliricidia sepium and A. zygia contributed more nitrogen derived from organic residue than rice husk and S. dinklagei but the mixture of A. zygia and G. sepium with rice husk enhanced N utilization.
Arbuscular Mycorrhizal Fungi Associated with Rice (Oryza sativa L.) in Ghana: E ect of Regional Locations and Soil Factors on Diversity and Community Assembly
(agronomy, 2020-04-12) Asuming-Brempong, S.; Sarkodee-Addo, E.; Yasuda, M.; Lee, C.G.; Kanasugi, M.; Fujii, Y.; Omari, R.A.; Abebrese, S.O.; Bam, R.; Dastogeer, K.M.G.; Okazaki, S.
Understanding the community composition and diversity of arbuscular mycorrhizal fungi (AMF) in an agricultural ecosystem is important for exploiting their potential in sustainable crop production. In this study, we described the genetic diversity and community structure of indigenous AMF in rain-fed rice cultivars across six di erent regions in Ghana. The morphological and molecular analyses revealed a total of 15 di erent AMF genera isolated from rice roots. Rhizophagus and Glomus were observed to be predominant in all regions except the Ashanti region, which was dominated by the genera Scutellospora and Acaulospora. A comparison of AMF diversity among the agroecological zones revealed that Guinea Savannah had the highest diversity. Permutational Multivariate Analysis of Variance (PERMANOVA) analysis indicated that the available phosphorus (AP) in the soil was the principal determining factor for shaping the AMF community structure (p < 0.05). We report, for the first time, AMF diversity and community structure in rice roots and how communities are a ected by the chemical properties of soil from di erent locations in Ghana.
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.
Author Correction: Effects of biochar, waste water irrigation and fertilization on soil properties in West African urban agriculture (Scientific Reports (2017) DOI: 10.1038/s41598-017-10718-y)
(Nature Publishing Group, 2018) Häring, V.; Manka'Abusi, D.; Akoto-Danso, E.K.; Werner, S.; Atiah, K.; Steiner, C.; Lompo, D.J.P.; Adiku, S.; Buerkert, A.; Marschner, B.
This Article contains errors in Figures 1, 4, 5, 7, 8 and 9, where the keys were omitted. The correct Figures 1, 4, 5, 7, 8 and 9 appear below as Figures 1, 2, 3, 4, 5 and 6 respectively. (Figure Presented). © 2018 The Author(s).
Biofertilizer Activity of Azospirillum sp. B510 on the Rice Productivity in Ghana
(Microorganisms, 2021) Sarkodee-Addo, E.; Tokiwa, C.; Bonney, P.; Aboagye, D.A.; Yeboah, A.; Abebrese, S.O.; Bam, R; Nartey, E.K.; Okazaki, S.; Yasuda, M.
Rice production in Ghana has become unsustainable due to the extremely nutrient-poor soils. It is caused by inadequate soil fertility management, including the inefficient application of fertilizers. A practical solution could be the biofertilizers, Azospirillum sp. B510. We performed field trials in Ghana and Japan to compare the effects of B510 colonization on selected Ghanaian rice varieties grown. The B510 inoculation significantly enhanced the rice cultivars’ growth and yield. The phenotypic characteristics observed in rice varieties Exbaika, Ex-Boako, AgraRice, and Amankwatia were mainly short length and high tillering capacity. These features are attributed to the host plant (cv. Nipponbare), from which the strain B510 was isolated. Furthermore, Azospirillum species has been identified as the dominant colonizing bacterium of rice rhizosphere across a diverse range of agroecologies in all major rice-growing regions in Ghana. Our results suggest that the utilization of B510 as a bio-fertilizer presents a promising way to improve rice growth, enhance soil fertility, and sustain rice productivity in Ghana.
Changes in the biodiversity of microbial populations in tropical soils under different fallow treatments
(Soil Biology and Biochemistry, 2008-11) Asuming-Brempong, S.; Gantner, S.; Adiku, S.G.K.; Archer, G.; Edusei, V.; Tiedje, J.M.
Favorable cropping systems that promote residue retention would normally lead to increased soil carbon storage. Experiments were conducted to test the hypothesis that soil carbon of different fallow management practices influences more the microbial biomass carbon and activity than the microbial community structure. Also, the distribution of the major microbial grouping in soil is influenced by how much carbon is sequestered in soil. Soils were sampled from the Kpeve Agricultural Experimental Station (KAES) in the Volta Region in Ghana. The treatments involved T1 - maize followed by fallow elephant grass that is burnt before planting, T3 - maize followed by pigeon pea fallow, T4 - maize followed by bare fallow, T7 - fertilized maize followed by elephant grass fallow, FR - forest reserve (unmanaged native vegetation). As the soil sequestered carbon, there was a corresponding increase in the microbial biomass carbon. The treatment effects were significantly different (p < 0.007). Correlation between biomass carbon and soil organic carbon was significant (r = 0.63*). Treatments with the least amount of carbon sequestered showed the least microbial activity. Significant relationship existed between dehydrogenase activity and the soil organic carbon (r = 0.683*). The phospholipid fatty acid (PLFA) analysis was used to assess the effect of different soil management practices on biodiversity of soil organisms. Differences in carbon sequestered in the treatments affected the percentage PLFA compositions of the various treatments, thus affecting the distribution. The amount of carbon sequestered in soil significantly influenced the proteobacteria (p < 0.001) and actinomycetes populations (p < 0.028). Thus, soils with high carbon storage showed high proteobacteria population and vice versa but the actinomycete population showed no particular trend with soil carbon. Diversity of the microbial community as assessed by the Shannon-Weiner Diversity Index showed no significant differences in treatments even though T4 had the highest diversity and FR the least diversity. The terminal Restriction Fragment Length Polymorphism on the soil DNA samples showed that the bacterial species' richness was greatest in T1 and T4. The most dominant bacterial groups were found in T1 and FR. Evenness was greatest in T7. We conclude from this study that the different fallow management practices influence the microbial biomass carbon and microbial activity. Secondly, the distribution of the major microbial grouping in soil is influenced by carbon stored in soil. © 2008 Elsevier Ltd.
Characterisation and rare-metal potential of the Winneba-Mankoadze pegmatites, Southern Ghana: Evidence of two pegmatite fields
(Journal of African Earth Sciences, 2023) Adams, S.J.; Lichtervelde, M.V.; Amponsah, P.O.; et al.
In southern Ghana, the region along the coast between Accra and Cape Coast hosts a large number of pegmatites mineralized in lithium, niobium-tantalum and tin. The pegmatites occur in many distinct groups, each extending over several kilometers. They intrude metasedimentary units of the Birimian Supergroup, and are associated with early to late orogenic granite intrusions which are metaluminous, sterile, and too old to be potential parental granites for the pegmatites. In this study, we characterized the Winneba-Mankoadze group of geographically coeval pegmatites, using field description, petrography, rare-metal mineralogy and accessory mineral geochemistry on micas, garnet and Nb–Ta–Sn minerals, in order to determine its rare-metal potential and to investigate its origin. The results indicate that the pegmatites are part of the albite-spodumene type of the Lithium–Cesium–Tantalum (LCT) family. The rare metal mineral assemblages are particularly complex and display relevant oxide species such as columbite- and wodginite-group minerals, tapiolite, microlite, cassiterite and rutile, which are evidences of an extremely evolved magmatic system. Based on mineral assemblages, whole rock geochemistry, and mineral geochemistry on garnet, micas and the CGM, two pegmatite fields are distin guished in the Winneba-Mankoadze group, and an anatectic origin is proposed. For the first time in West Africa, we fully describe a highly fractionated LCT-family pegmatite field comparable to the most evolved pegmatite bodies in the world.
Characterization and diversity of rhizobia nodulating selected tree legumes in Ghana
(Symbiosis, 2016-02) Boakye, E.Y.; Lawson, I.Y.D.; Danso, S.K.A.; Offei, S.K.
The study was conducted to assess the characteristics and diversity of the rhizobia that nodulate some prominent tree legumes in three soils of Ghana. Five introduced and/or indigenous tree legumes were initially assessed for nodulation in three Ghanaian soils. After 12 weeks of growth in nursery pots the 200 rhizobial strains isolated from their nodules were characterized culturally, metabolically and phenotypically. Sixty of these isolates were selected randomly and their genotypic characteristics determined using PCR-RFLP of 16S rRNA and intergenic spacer (ITS) genes. Each tree legume was nodulated by isolates classified as fast or very fast-growers or by isolates classified as slow- or very slow-growers with 54 % of all the 200 isolates belonging to fast- or very fast-growers. Morphologically, eighty five percent of the colonies formed on yeast extract mannitol agar were wet and gummy while 70 % were acid tolerant, i.e. they were able to grow at a pH of 3.5. Combined restriction of the 16S rRNA genes of the 60 rhizobial isolates with five restriction enzymes clearly distinguished seven different clusters at 80 % similarity level. The majority of A. lebbeck isolates were distinct from those of the Acacias and L. leucocephala. The M. thonningii isolates were related to L. leucocephala isolates. Simple PCR of the ITS DNA provided several distinct band sizes indicating great variation among the isolates and restriction of the ITS with three different enzymes did not yield many further differences. Molecular techniques revealed a great diversity among the rhizobia that nodulate tree legumes in the tropics and this may explain why many introduced and/or indigenous trees are able to form nodules with indigenous rhizobia in this region. © 2016, The Author(s).
Characterization of charcoal and firewood ash for use in African peri‑urban agriculture
(Chemical and Biological Technologies in Agriculture, 2020-03-05) Neina, D.; Faust, S.; Joergensen, R.G.
Background: Ample quantities of ashes generated from domestic biomass energy combustion in Ghanaian kitchens are currently disposed of despite their potential agricultural value. This study aimed to investigate the potential agricultural value of charcoal and firewood ashes in terms of differences in the chemical and mineralogical compositions, and to identify the suitability of aqua regia, H2SO4, vinegar and distilled water to extract plant nutrients (Ca, Mg, K, Na, and P). The chemical compositions were determined by atomic absorption spectrometry after extractions with aqua regia, H2SO4, vinegar and distilled water while mineralogy was determined by X-ray powder diffraction. Results: The charcoal ash had 0.2 units, 13 ds m−1, and 7% higher (P < 0.05) pH, EC, and CCE, respectively, than the firewood ash, whereas the latter had 6, 17, 43, and 139 μg g−1 higher (P < 0.05) As, Cu, Mg, and Zn contents, respectively, and more minerals with 86% being Mg-rich. Calcite and calcium oxide were the dominant minerals occurring in both ashes followed by calcium manganate ( CaMnO3). Aqua regia and vinegar were suitable for Ca, acidic solutions for Mg, H2SO4 and aqua regia for P with Na and K being virtually soluble in all solutions. Lead, Mn, Ni, and Zn had values in the order of hundreds. Conclusions: Although the ashes differ, they both contain trace elements whose bioavailability may differ and may not necessarily lead to plant uptake after field application. This offers an opportunity for further research into the threshold trace element contents of wood ash and their relationship with plant uptake in different soil pH and soil types.
Characterizing market crop waste as feedstock for composting to reduce environmental pollution in developing countries
(Islamic Azad University, 2023) Nartey, E.K.; Akumah, A.M.; Ofosu-Budu, G.K.; et al.
Abstract Purpose Market crop waste (MCW) contributes significantly to the quantity of municipal solid waste generated in sub-Saharan Africa. These wastes, however, contain high levels of plant nutrients which can be harnessed through composting to improve soil organic matter and nutrient status of impoverished tropical soils. Method In this work, annual MCWs from two urban markets in Accra, Ghana were characterized by quantifying their seasonal availabilities, primary nutrients, heavy metals concentrations and level of microbial contamination to ascertain their suitability or otherwise for composting. Results Waste generated in the rainy seasons was higher than in the dry seasons. Primary nutrients sequestered in the MCW collected were 211.1 kg N, 1.84 kg P and 89.66 kg K for both markets. Feedstock quality analysis showed heavy metal levels in the MCW were far below the contaminant levels. Moisture content of vegetable and fruit waste was 74.34 - 90.46% and far above the desired level of aerobic composting. Pathogen levels of 5.92 CFU/g E. coli and 5.41 CFU/g Salmonella in cocoyam leaves; 6.27 CFU/g total coliform and 4.74 CFU/g Enterococcus in cabbage were detected and found to be above the maximum contaminant level as per USEPA standard. Conclusion Use of cassava, plantain peduncle and corn husk as bulking agents with vegetable and fruit waste as N, P and K sources should serve as feedstock for good quality compost production.
Characterizing Repeats in Two Whole-Genome Amplification Methods in the Reniform Nematode Genome
(Hindawi, 2021) Nyaku, S.T.; Sripathi, V.R.; Lawrence, K.; Sharma, G.
One of the major problems in the U.S. and global cotton production is the damage caused by the reniform nematode, Rotylenchulus reniformis. Amplification of DNA from single nematodes for further molecular analysis can be challenging sometimes. In this research, two whole-genome amplification (WGA) methods were evaluated for their efficiencies in DNA amplification from a single reniform nematode. The WGA was carried out using both REPLI-g Mini and Midi kits, and the GenomePlex single cell whole-genome amplification kit. Sequence analysis produced 4 Mb and 12 Mb of genomic sequences for the reniform nematode using REPLI-g and SIGMA libraries. These sequences were assembled into 28,784 and 24,508 contigs, respectively, for REPLI-g and SIGMA libraries. The highest repeats in both libraries were of low complexity, and the lowest for the REPLI-g library were for satellites and for the SIGMA library, RTE/BOV-B. The same kind of repeats were observed for both libraries; however, the SIGMA library had four other repeat elements (Penelope (long interspersed nucleotide element (LINE)), RTE/BOV-B (LINE), PiggyBac, and Mirage/P-element/Transib), which were not seen in the REPLI-g library. DNA transposons were also found in both libraries. Both reniform nematode 18S rRNA variants (RN_VAR1 and RN_VAR2) could easily be identified in both libraries. This research has therefore demonstrated the ability of using both WGA methods, in amplification of gDNA isolated from single reniform nematodes.
Co-Composted Chicken Litter Biochar Increases Soil Nutrient Availability and Yield of Oryza sativa L.
(Land, 2023) Ali, M; Ahmed, O.H.; Jalloh, M.B.; Primus, W.C.; et al.
Intensified cultivation of rice has accelerated weathering of most tropical acid soils leading to significant loss of base cations. In most developing countries, rice yield is low and this results in its production being costly because productivity versus labor is low. The objectives of this study were to (i) enhance soil chemical properties, nutrient uptake, and grain yield of rice grown on a mineral tropical acid soil using agro-wastes; (ii) determine the agro-waste (chicken manure, cow dung, forest litter, and Leucaena) that has the potential to significantly increase rice yield; and (iii) determine the residual effects of the organic soil amendments produced from the agro-wastes on soil and rice productivity. The treatments used in this three-cycle field study were (i) soil without amendments (S0); (ii) prevailing recommended rates for fertilizers (NPK-Mg); (iii) biochar–forest litter compost (OSA1); (iv) biochar–chicken litter compost (OSA2); (v) biochar–cow dung compost (OSA3); (vi) biochar–Leucaena compost (OSA4); and (vii) biochar–Leucaena–chicken litter compost (OSA5). Standard procedures were used to determine the plants’ rice growth, grain yield, plant nutrient concentrations and uptake, and selected soil chemical properties. The use of organic soil amendments (OSA1 to OSA5) significantly improved the soil chemical properties, rice plant growth, nutrient uptake, and grain yield compared with the prevailing method of cultivating rice (NPK-Mg). The application of organic soil amendments reduced the use of inorganic N, P, K, MgO, and trace elements fertilizers up to 25%, 100%, 64%, 100%, and 100%, respectively. The organic soil amendments with Leucaena significantly increased rice grain yield of OSA5 at 11.17, 13.11, and 10.06 t ha−1 in the first, second, and third cropping cycles, respectively. The residual effect of the organic soil amendments also improved rice plant growth, nutrient uptake, and rice grain yield although these were slightly reduced as compared to those of the two previous cropping cycles, the afore-stated treatments were superior to the prevailing method of cultivating rice (NPK-Mg). Transforming agro-wastes into organic soil amendments can improve tropical mineral acid soils and rice productivity
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.
Comparison of greenhouse and 32P isotopic laboratory methods for evaluating the agronomic effectiveness of natural and modified rock phosphates in some acid soils of Ghana
(Nutrient Cycling in Agroecosystems, 2002-05) Owusu-Bennoah, E.; Zapata, F.; Fardeau, J.C.
Phosphorus deficiency is one of the major constraints for normal plant growth and crop yields in the acid soils of Ghana and therefore addition of P inputs is required for sustainable crop production. This is often difficult, if not impossible for small-scale farmers due to the high cost of mineral P fertilizers and limited access to fertilizer supplies. Direct application of finely ground phosphate rocks (PRs) and their modified forms have been recommended as alternatives for P fertilization. The direct application of the natural and modified PRs to these acid soils implies the need to predict their agronomic effectiveness of the PRs in the simplest and most cost-effective manner. In this study the classical greenhouse pot experiment was compared to the 32P isotopic kinetics laboratory method for evaluating the agronomic effectiveness of natural and modified Togo PR in six highly weathered Oxisols from southwest Ghana. In the 32P isotopic kinetics laboratory experiment the six soil samples were each fertilised at the rate of 50 mg P kg-1 soil in the form of triple superphosphate (TSP), Togo PAPR-50%, and Togo PR, respectively. Controls without P amendment were also included. Isotopic exchange kinetics experiments were carried out on two sets of samples, immediately after P fertilizer additions (without incubation) and after 6 weeks of incubation under wet conditions and at a room temperature of 25 °C. In the greenhouse pot experiment, P fertilizers in the form of Togo PR, Togo PAPR, Mali PR and TSP were each applied to the six soils at rates equivalent to 0, 30, 60, and 120 kg P ha-1, respectively. The P fertilizers were mixed with the soils and maize (Zea mays L.) variety Obatanpa was grown for 42 days before harvest. The isotopic kinetics data of the control samples indicated that 5 of the studied soils had very low P fertility status as reflected by their low P concentrations in solution (CP<0.02 mg P 1-1) and low exchangeable P (E1min < 5 mg P kg-1). The capacity factor and the fixation index of the soils were variable. Application of water-soluble P as TSP increased both the CP and E1 values of all the soils above the critical levels. Togo PR was least effective among the fertilizers tested for all soil soils, except in Boi soil. Acidulation of Togo PR (Togo PAPR-50%) was an effective means to increase its agronomic effectiveness. Direct application of natural Togo PR would be only feasible in the Boi soil series as reflected by its high Pdff% value in soil solution. Incubation with the P fertilizers caused an increase in the soil pH and a decline in the effectiveness of the applied P fertilizers, irrespective of the soil and the fertilizer utilized. Based upon the results of the greenhouse pot experiment, the relative crop response index (RCRI) in terms of increasing dry matter yield and P uptake followed the order of TSP > PAPR = Mali PR >Togo PR = Control. Both the laboratory index, Pdff% in soil solution derived from the isotopic method and the RCRI values obtained from the pot experiment produced similar results in ranking the P fertilizers tested according to their agronomic effectiveness. The isotopic kinetic method may be considered as an alternative to both greenhouse and field methods in the evaluation of agronomic effectiveness of P fertilizers in tropical acid soils when it offers comparative advantages in assessing the soil P status and its changes. But trained staff and adequate laboratory facilities are needed to perform this technique. Also the method can be used as a reference for comparison purposes as in this case. Further research is needed to assess the overall agronomic effectiveness (immediate and residual effects) of PR sources in predominant cropping systems of this region of Ghana.
Conceptual methodologies in agro-environmental systems
(Soil and Tillage Research, 2001-03) Rose, C.W.; Adiku, S.
When continuous measurement of relevant above- and below-ground environmental factors is made, and the dynamics of crop growth and phenology is followed, it is shown that small-plot agronomic experimentation can provide information vital to the development and testing of simulation models. Such models for crops of maize (Zea mays) and the legume cowpea (Vigna unguiculata), grown as sole crops and in an intercrop system, were used to simulate yield at two separate sites in the main savanna farming zones in Ghana, West Africa. Simulation was carried out for these three cropping systems using 20 years of historical rainfall data for the two sites, investigating the effect on yield of management options which included time of planting, rate of nitrogen fertilizer application, and crop planting density. The yield results of this series of simulations were then subject to two different types of analysis in order to assist the evaluation of agricultural options for the nation. The first analysis was an economic evaluation based on gross margins, but using the stochastic-dominance technique to rank the profitability of the alternative cropping and management systems. The second, more general methodology employed was multi-criteria analysis (MCA). This analysis covered economic returns and their variability, the amount and quality of residue returned to the soil, and the aerial cover provided by the crop. Other factors which could affect the sustainability of production in the long term, but which could only be evaluated qualitatively, were also included in the analysis, as allowed in MCA methodology. The MCA was then carried out for three scenarios in which different weightings were given to economic outcomes and to factors which are believed to encourage ecological sustainability. These scenarios allow recognition of different priorities which might be given by traditional subsistence farmers as compared to commercial producers. Outcomes of this broad analysis of development alternatives provided scientific support for the traditional Ghanaian practice of grain/legume intercropping which is also widespread in the tropics. The suite of methodologies illustrated by the case study appears to be suitable for the evaluation of alternative farming systems at the scale of a small nation such as Ghana. © 2001 Elsevier Science B.V.

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