Prof Kolawole Salako (Abeokuta - NG)

Deputy Vice-Chancellor (Development) and Professor of Soil Physics, University of Agriculture, Abeokuta

Gunnar Kirchhof

Recent Publications

Sotona, T. Salako, FK. Adesodun, JK. 2014. Soil physical properties of selected soil series in relation to compaction and erosion on farmers' fields at Abeokuta, southwestern Nigeria. ARCHIVES OF AGRONOMY AND SOIL SCIENCE. 60, 841-857.

This study evaluated physical properties of selected soil series and their implications on the soil compaction and erosion in Abeokuta, southwestern Nigeria. Daily rainfall data (1999-2007) were collected to estimate the rainfall erosivity. Seven soil series (Iwo, Iseyin, Ekiti, Jago, Okemesi, Apomu, and Egbeda) were sampled from 0-15, 15-30, and 30-50cm depths for particle size distribution, organic carbon, pH, upper plastic limit, and compactibility (Proctor test). Microtopographical changes along and across toposequences of two farmers' fields cleared mechanically and manually, respectively, were monitored using the erosion pin method. Mean annual erosivity (EI30) was high (7646 MJ mm ha(-1) hr(-1)). Particle size, organic carbon, and pH were similar (p0.05), while upper plastic moisture was2% among different soil series. Soil-moisture density curves indicated a maximum bulk density of 1.77-1.99gcm(-3) for a moisture range of 7.6-14%; while the soils were prone to compaction at low moisture content. Microtopographic changes were found between -2 and 0cm and -8 and -2cm on mechanically and manually cleared farmland, respectively. Spatial dependence showed that the soil erosion could be predicted within 5-8m distance. To avoid erosion and compaction, soil water content should be less than 7.6% before the introduction of mechanical tillage.

Busari, MA. Salako, FK. Tuniz, C. Zuppi, GM. Stenni, B. Adetunji, MT. Arowolo, TA. 2013. Estimation of soil water evaporative loss after tillage operation using the stable isotope technique. INTERNATIONAL AGROPHYSICS. 27, 257-264.

Application of stable isotopes in soil studies has improved quantitative evaluation of evaporation and other hydrological processes in soil. This study was carried out to determine the effect of tillage on evaporative loss of water from the soil. Zero tillage and conventional tillage were compared. Suction tubes were installed for soil water collection at the depths 0.15, 0.50, and 1.0 m by pumping soil water with a peristaltic pump. Soil water evaporation was estimated using stable isotopes of water. The mean isotopic composition of the soil water at 0.15 m soil depth were -1.15 parts per thousand (delta O-18) and -0.75 parts per thousand (delta D) and were highly enriched compared with the isotopic compositions of the site precipitation. Soil water stable isotopes (delta O-18 and delta D) were more enriched near the surface under zero tillage while they were less negative down the profile under zero tillage. This suggests an occurrence of more evaporation and infiltration under conventional then zero tillage, respectively, because evaporative fractionation contributes to escape of lighter isotopes from liquid into the vapour phase leading to enrichment in heavy isotopes in the liquid phase. The annual evaporation estimated using the vapour diffusion equation ranges from 46-70 and 54-84 mm year(-1) under zero and conventional tillage, respectively, indicating more evaporation under conventional tillage compared with zero tillage. Therefore, to reduce soil water loss, adoption of conservation tillage practices such as zero tillage is encouraged.

Salako, F. K. (2010). Development of isoerodent maps for Nigeria from daily rainfall amount. Geoderma 156(3-4): 372-378.

In this study, rainfall erosivity factor, R. of the Revised Universal Soil Loss Equation (RUSLE) was estimated from daily rainfall amounts of the coastal, humid forest, savanna, semi-arid and arid zones of Nigeria using data from 17 locations, which spanned 10-33 years. Two power law equations were applied to compute the products of kinetic energy, e, and (i) maximum 30-minute intensity, I(30) (EI(30)), and (ii) maximum 15-minute intensity, I(15) (EI(15)). The indices were used to develop monthly and annual isoerodent maps. Mean monthly EI(30) ranged from 600 to 3200 MJ mm ha(-1) h(-1) whereas the annual values ranged from 3000 to 27,000 MJ mm ha(-1) h(-1) from the arid to the coastal zones. The EI(15) index was 1.7 times greater than the EI(30). Trends of rainfall erosivity in the derived, southern Guinea and northern Guinea savannas or wet savannas were erratic and less predictable from the trends of rainfall amount, unlike in the coastal, humid forest, semi-arid and arid zones. Extrapolation of data for soil conservation planning did not appear feasible in the wet savannas. Monthly values of erosivity presented are recommended for conservation plans during the cropping seasons in the various agroecological zones. The EI(15) index is recommended for both monthly (seasonal) and annual soil loss computations because short-term intensities reveal rainfall erosivity better in the tropics.

Salako, FK. 2010. Development of isoerodent maps for Nigeria from daily rainfall amount. Geoderma. 156, 372-378.

In this study, rainfall erosivity factor, R. of the Revised Universal Soil Loss Equation (RUSLE) was estimated from daily rainfall amounts of the coastal, humid forest, savanna, semi-arid and arid zones of Nigeria using data from 17 locations, which spanned 10-33 years. Two power law equations were applied to compute the products of kinetic energy, e, and (i) maximum 30-minute intensity, I(30) (EI(30)), and (ii) maximum 15-minute intensity, I(15) (EI(15)). The indices were used to develop monthly and annual isoerodent maps. Mean monthly EI(30) ranged from 600 to 3200 MJ mm ha(-1) h(-1) whereas the annual values ranged from 3000 to 27,000 MJ mm ha(-1) h(-1) from the arid to the coastal zones. The EI(15) index was 1.7 times greater than the EI(30). Trends of rainfall erosivity in the derived, southern Guinea and northern Guinea savannas or wet savannas were erratic and less predictable from the trends of rainfall amount, unlike in the coastal, humid forest, semi-arid and arid zones. Extrapolation of data for soil conservation planning did not appear feasible in the wet savannas. Monthly values of erosivity presented are recommended for conservation plans during the cropping seasons in the various agroecological zones. The EI(15) index is recommended for both monthly (seasonal) and annual soil loss computations because short-term intensities reveal rainfall erosivity better in the tropics. (C) 2010 Elsevier B.V. All rights reserved.

Busari, M. A., F. K. Salako, M. T. Adetunji and N. J. Bello (2009). Effect of selected soil amendments on physical properties of an Alfisol in Abeokuta southwestern Nigeria. Nigerian Journal of Soil Science 19(1): 93-99.

This study was carried out in 2004 and 2005 at Ajegunle Farm Settlement Scheme's site, near Abeokuta, southwestern Nigeria. A factorial experiment in randomized complete block design with 3 replicates was set up. The factors were poultry manure (0, 5 and 10 t ha -1), lime as CaCO 3 (0 and 250 kg ha -1) and NPK 15-15-15 (0 and 100 kg ha -1). Maize (TZSR-Y) was planted. Soil physical properties measured included dry bulk density, saturated hydraulic conductivity ( Ks), unsaturated water flow and clay dispersion ratio (CDR). The range of surface soil bulk density, from 1.27-1.42 g cm -3, observed for poultry manure application was significantly lower than the range of 1.39-1.48 g cm -3, when manure was not applied. The highest Ks value of 1.70 cm min -1 from plot applied with 10 t ha -1 poultry manure (PM) was significantly higher than 0.41-0.49 cm min -1 from all inorganically treated plots and the control. At the end of the second cropping season, application of poultry manure especially at 10 t ha -1 reduced the CDR from 17.1% to a range of 15.7%-9.3%, thereby increasing the soil aggregate stability. Application of 10 t ha -1 Poultry manure significantly improved the infiltration rate of the field. Integrated use of lime or 10 t ha -1 Poultry manure with NPK as well as application of 10 t ha -1 poultry manure only, improved the ability of soil to transmit water (sorptivity) under unsaturated condition. Combined application of poultry manure with inorganic amendments is therefore important in the improvement of physical properties of the soil.

Nosiru, N. A., F. K. Salako, O. Martins and N. J. Bello (2009). Potential soil erosion, river sedimentation and pollution risks from selected watersheds at Abeokuta, southwestern Nigeria. Nigerian Journal of Soil Science 19(1): 129-136.

Potential soil erosion, sedimentation and water pollution risks were assessed on the landscape of the University of Agriculture, Abeokuta, southwestern Nigeria. Potential soil loss was estimated using the Universal Soil Loss Equation (USLE) while sedimentation and pollution risks were assessed from sediment and water samples taken every 2 weeks from August-December, 2004 from five rivers. For the USLE, rainfall erosivity factor, R, was estimated using the modified Fournier index; soil erodibility was estimated using Wischmeier and Smith nomograph after analyzing surface (0-20 cm depth) soil samples from the watersheds. The topographic factor, LS, was estimated from topographic maps. Annual rainfall erosivity factor, R, was 9829 MJ mm ha -1 h -1, suggesting that Fournier index agreed with other annual R values calculated with intensity-based models for the agroecological zone. Potential soil losses ranged from 1.5-49 Mg ha -1 a -1 whereas the mean suspended sediment loads in river waters ranged from 442-1098 mg cm -3. Sediment enrichment ratio was between 0.48 and 0.64. Water quality for drinking was good based on pH, Cl -, Na + and Fe 2+ but Zn 2+ levels might not be acceptable. Also, based on these chemical properties, electrical conductivity and sodium adsorption ratio, the river waters were rated good for irrigation of crops. Watersheds in the built-up areas had the higher soil erosion and water pollution risks that those under forest. The need to adopt soil conservation measures on all watersheds was highlighted.

Salako, F. K. (2009). Isolines of rainfall kinetic energy and intensity in Nigeria. Nigerian Journal of Soil Science 19(2): 153-158.

Based on the power law equations developed by Salako (2006; 2007; 2008), daily rainfall data (generally 1988-2005) were collected from 17 weather stations in Nigeria (representing all agroecological zones in the country) to compute kinetic' energy of rainfall and IS-minute intensity, 1/5. The Wischmeicr and Smith (1978) kinetic index. EWS was similar to Brown and Foster (1987) index, E-BF. Isolines of rainfall kinetic energy and intensity were drawn with SURFER Version 8. Kinetic energy and rainfall intensity increased, generally, from the coastal region of the southeast in the northwestward direction. There were, however, abrupt changes in both characteristics between latitude 7 and 1ION, mainly in the derived, southern Guinea (SGS) and northern Guinea (NGS) savannas. Sholi-term rainfall intensities could be similar among regions in spite of significant differences in cumulative rainfall amount or kinetic energy. Kinetic energy measured at a monthly scale showed less spatial variation than that on daily scale, suggesting that long timescale could obscure useful details. Rainfall erosivity trends across the country suggest a possible influence of the migration of the Intertropical Convergence Zone (ITCZ). The maps presented can be used to decide spacing for locations of monitoring centers for soil and water management in the country.

Busari, M. A., F. K. Salako and M. A. Adetunji (2008). Soil chemical properties and maize yield after application of organic and inorganic amendments to an acidic soil in southwestern Nigeria. Spanish Journal of Agricultural Research 6(4): 691-699.

A factorial experiment with a randomised complete block design (three replicates) was performed to determine the effects of poultry manure (PM), lime (L) and NPK 15-15-15 fertilizer on soil chemical properties, and to determine the effects of their combinations on soil productivity and maize yield. The factors were PM (0, 5 and 10 Mg ha(-1)), L as CaCO(3) (0 and 250 kg ha-1) and NPK 15-15-15 (0 and 100 kg ha-1). The soil had a loamy sand texture. The application of L and PM increased the surface soil pH in a similar fashion. In both years of the experiment, the effective cation exchange capacity (ECEC) of the soil after the combined application of 10 Mg ha-1 PM, L and NPK was significantly higher than after the individual application of L or NPK or their combination (5.75-7.65 cmol kg(-1) compared to 3.36-4.57 cmol kg(-1)). The application of 10 Mg ha(-1) PM with L and/or NPK reduced the possibility of Mn toxicity, with soil levels ranging from 108 to 136 mg kg(-1). The combined use of the three amendments gave the highest leaf nutrient concentrations. The highest maize grain yield (4.62 Mg ha-1) was obtained with L + 10 Mg ha-1 PM; with no amendment the grain yield was 1.9 Mg ha-1. The application of PM enhanced the effects of L and NPK in improving soil productivity. However, separate applications of 5 and 10 Mg ha-l PM similarly affected soil productivity; the sandy nature of the soil at depths of 0-20 cm seems to have prevented differences between the two rates from becoming manifested.

Busari, M. A., F. K. Salako, Adetunji, M. A. (2008). Soil chemical properties and maize yield after application of organic and inorganic amendments to an acidic soil in southwestern Nigeria. Spanish Journal of Agricultural Research 6(4): 691-699.

A factorial experiment with a randomised complete block design (three replicates) was performed to determine the effects of poultry manure (PM), lime (L) and NPK 15-15-15 fertilizer on soil chemical properties, and to determine the effects of their combinations on soil productivity and maize yield. The factors were PM (0, 5 and 10 Mg ha(-1)), L as CaCO3 (0 and 250 kg ha-1) and NPK 15-15-15 (0 and 100 kg ha-1). The soil had a loamy sand texture. The application of L and PM increased the surface soil pH in a similar fashion. In both years of the experiment, the effective cation exchange capacity (ECEC) of the soil after the combined application of 10 Mg ha-1 PM, L and NPK was significantly higher than after the individual application of L or NPK or their combination (5.75-7.65 cmol kg(-1) compared to 3.36-4.57 cmol kg(-1)). The application of 10 Mg ha(-1) PM with L and/or NPK reduced the possibility of Mn toxicity, with soil levels ranging from 108 to 136 mg kg(-1). The combined use of the three amendments gave the highest leaf nutrient concentrations. The highest maize grain yield (4.62 Mg ha-1) was obtained with L + 10 Mg ha-1 PM; with no amendment the grain yield was 1.9 Mg ha-1. The application of PM enhanced the effects of L and NPK in improving soil productivity. However, separate applications of 5 and 10 Mg ha-l PM similarly affected soil productivity; the sandy nature of the soil at depths of 0-20 cm seems to have prevented differences between the two rates from becoming manifested.

Salako, F. K. (2008). Estimation of evapotranspiration with FAO-56 Penman-Monteith equation for three agroecological zones of Nigeria. ASSET - Series A: Agriculture & Environment 8(1/2): 134-149.

The Food and Agriculture Organisation (FAO) irrigation and drainage Paper 56 recommends the use of Penman-Monteith ( PM) method for calculating reference evapotranspiration ( ET 0 ). This method has been widely accepted. Alternative methods recommended where data requirements for the PM cannot be met are Hargreaves ( HG) and pan methods. Therefore, this study was carried out to evaluate ET0 with the PM method and develop its relationship with HG and pan methods for Onne (humid), Ibadan (sub-humid) and Kano (semi-arid), Nigeria using 1990-2005 daily climatic data. The data were resolved to daily means of each week of the year, and monthly and annual totals. Deviations of the data from long-term means were determined and the ET0 methods were compared using root mean square error ( RMSE) and mean bias error ( MBE). Autocorrelation coefficients and regression analysis were also carried out. The daily means for each week with PM ET0 ranged from 2.39-3.82 mm in Onne, 2.45-4.48 mm in Ibadan and 3.62-7.92 mm in Kano. Mean annual PM ET0 was 1130 mm vs. 2450 mm of rainfall in Onne; 1249 mm in Ibadan vs. 1286 mm of rainfall and 2007 mm in Kano vs. 786 mm of rainfall. The HG method over-predicted PM ET0 in Onne and Ibadan and under-predicted it in Kano. The pan method under-predicted it in Onne and Ibadan. Nonetheless, the HG method was a better estimator of PM ET0 in Kano than Onne and Ibadan, although daily means in the dry season were more variable. Daily means of PM ET0 were significantly related to means HG ET0 ( P

Salako, F. K. (2008). Rainfall variability and kinetic energy in Southern Nigeria. Climatic Change 86(1-2): 151-164.

A decreasing trend of rainfall has been observed in West Africa, where rainfall erosivity is also considered to be high. Therefore, this study was carried out to evaluate the variability of rainfall and its erosivity in two contrasting zones in southern Nigeria between 1977 and 1999 to understand the implications of climate variability on rainfall erosivity. The study sites were Ibadan, a sub-humid zone, and Port-Harcourt, a humid zone. Time of occurrence of rainfall, rainfall amount (A), intensity (I-15 and I-30), kinetic energy (E) and rainfall erosivity factor (R), were evaluated. Kinetic energy was estimated with Brown Foster (BF) equation, making the rainfall erosivity (product of kinetic energy and intensity) to be designated as EI30-BF and EI15-BF. The frequency of rainfall during daylight (06:00-18:00 h) was 48% for Ibadan and 69% for Port-Harcourt. There were time-specific differences in daily rainfall occurrence between the zones, suggesting a strong influence of local effects on rainfall generation, such as, relief in Ibadan and proximity to the sea in Port-Harcourt. Annual E was 213 MJ ha(-1)for Ibadan and 361 MJ ha(-1) for Port-Harcourt. Ibadan had a significantly higher daily E than Port-Harcourt because of higher intensity while Port-Harcourt had significantly higher annual E than Ibadan because of higher annual rainfall amount. Annual erosivity at Ibadan using the EI30-BF was 9,742 MJ mm ha(-1) h(-1) whereas it was 15,752 MJ mm ha(-1) h(-1) at Port-Harcourt. Using the EI15-BF, Ibadan had an annual value of 14,806 MJ mm ha(-1) h(-1) while Port-Harcourt had 20,583 MJ mm ha(-1) h(-1). Thus, annual rainfall erosivity was significantly higher in the humid than the sub-humid zone because of higher amount of rainfall but the reverse was the case with daily erosivity because of higher intensities in the sub-humid zone. Rainfall intensity was, therefore, a key measure of erosivity. There was a strong positive relationship between rainfall erosivity and rainfall amount. Between 1977 and 1988, 50-88% of the 12 years had rainfall erosivity which exceeded the long-term average but rainfall erosivity was less than the long-term average between 1989 and 1999. This suggested a decreasing trend in erosivity due to the decreasing trend in rainfall amount in West Africa. However, the trend did not imply lesser soil erosion and environmental degradation risks.

Kirchhof, Odunze, Salako, SOIL MANAGEMENT PRACTISES IN THE NORTHERN GUINEA SAVANNA OF NIGERIA, IN: Soil fertility in sweet potato-based cropping systems in the highlands of Papua New Guinea, 2009, ACIAR Technical Reports 71, Editor G. Kirchhof, p43-48. (http://www.aciar.gov.au/publication/TR71)

A survey of soil management practices was conducted in the northern Guinea savanna of Nigeria. Fifteen villages were randomly selected from a geographical grid covering an area of 100 × 200 km located in the benchmark area of the Ecoregional Program for the Humid and Sub-humid Tropics of Sub-Saharan Africa. In each village the chief and several farmers were interviewed to assess their soil management methods and attitude towards the need to conserve soil. A total of 181 farmers were interviewed in late 1996. The most common crop rotation systems were food legumes with non-legume crops (40%), followed by monocropping (28%). Fifty-three per cent of the farmers who included food legumes in their rotations did so for soil fertility considerations, while 49% of the farmers who practised monocropping did so to maximise their output. These practices indicate that farmers were well aware of the importance of legumes for maintaining soil fertility. Only 2% of the farmers practised mulching with crop residue. The most common use of crop residue was for fodder, the remainder largely being used as building material or else burnt. As a consequence, soil surfaces were generally bare at the onset of the rainy season and hence prone to soil erosion. Ridging was the most important land preparation technique (88%), with farmers perceiving benefit in terms of improved crop emergence (56%) and water conservation (11%). Other benefits included weed control. Ridging was generally practised along contours, with most farmers citing soil conservation benefits, e.g. water conservation, and erosion control as the reasons for using contour ridging. Those farmers who purposely ridged up and down the slope did so for drainage purposes. All farmers used the same method to build ridges—the ridge from the previous year was cut in the middle and the two halves of neighbouring ridges were combined to form a new ridge in the furrow from the previous year. According to the farmers, this method controlled weeds and improved emergence. None of the farmers practised rebuilding old ridges, similar to permanent ridges. Such a practice might be acceptable to farmers in that it may be less labour intensive to rebuild partially collapsed ridges compared to reridging completely. Soil physical benefits from semi-permanent ridging would include increased soil structural stability, reduced soil compaction and increased root proliferation into the subsoil. Negative side effects might include reduced crop emergence and increased weed infestation. The most commonly used tools for soil preparation were hand hoes (80%), followed by draft animals (16%) and tractors (3%).

Salako, F. K., Tian, G., Kirchhof G. 2008. Soil chemical properties and crop yields on an eroded Alfisol managed with herbaceous legumes under yam-maize rotation. Nigerian Journal of Soil Science 18:1-9

This study was carried out in Ibadan, southwestern Nigeria between 1997 and 1999 to determine changes in soil chemical properties and yields on a previously eroded Alfisol. A factorial experiment in which legumes (Vigna unguiculata (cowpea), Mucuna pruriens and Pueraria phaseoloides) and residue management (burned and mulched residues) were factors was set up in two replicates of runoff plots. Yam was planted in 1997 and 1999 whereas maize + legume intercrops were planted in 1997. Soil properties measured were particle size distribution, pH, organic C, total N, Ca, Mg, Mn, exchangeable acidity and effective cation exchange capacity. There was increased acidity at the site. Soil chemical properties were significantly improved by burning of cowpea and Pueraria residues and mulching with Mucuna. Yam tuber yields of 14-18 t ha-1 in 1997 was

Total of more than 60 publications, including 36 in international peer reviewed Journals.

Education/Qualifications

1997

Ph. D. (Soil Science) Department of Agronomy, University Of Ibadan, Nigeria.

1986

M.Sc. (Soil Physics and Conservation). Department of Soil Science, University of Nigeria, Nsukka, Nigeria

1983

B. Agric (Soil Science). Department of Soil Science, University of Nigeria, Nsukka, Nigeria

Work History and Experience

since 2000

University of Agriculture, Abeokuta, Department of Soil Science and Land, Nigeria

Reader in Soil Science:

Lecturing

Soil research and development

1989 - 2000

International Institute of Tropical Agriculture, IITA Ibandan, Nigeria.

Research Associate:

Consultancy

Food and Agriculture Organization (FAO), Rome

Memberships

Languages

English (official), Yoruba (native)