Nigerian Journal of Soil Science

Effect of Tillage on Soil Properties and Yield of Sorghum (Sorghum Bicolor (L.) Moench) in Southwest Nigeria

T Agbede

Field experiments were carried out at two locations in late-season 2004, early-season 2005 and lateseason 2006 on an Alfisol of southwest Nigeria to assess the effect of five tillage methods on soil properties and yield of sorghum. The tillage treatments were zero tillage, manual clearing, ploughing, ploughing plus harrowing and ploughing plus harrowing twice. The surface soils (0-15 cm) were chemically analysed before and after second and third experiments and selected soil physical properties were determined. Zero tillage and manual clearing reduced soil temperature and conserved more soil water better than mechanized tillage systems. Soil pH, organic matter, N, P, K, Ca and Mg were significantly influenced (p=0.05) by tillage with zero tillage being the most effective treatment in conserving fertility of the surface soil (0-15 cm). Soil fertility, as indicated by soil pH, organic matter, N, P, K, Ca and Mg declined significantly (p=0.05) over time in all tillage systems, but this decline was more pronounced in the ploughing plus harrowing twice. Zero tillage followed by manual clearing resulted in higher grain yield of sorghum compared with mechanized tillage systems. Average over the years, zero tillage, manual
clearing, ploughing and ploughing plus harrowing out-yielded ploughing plus harrowing twice by 33.7, 30.5, 18.9 and 17.9%, respectively in grain yield. Soil bulk density ranging from 1.28-1.58 Mg m-3 correlated positively with yield. Sorghum can be grown successfully on zero tillage and manually cleared Alfisol of the humid tropics.

Soil Properties and Yam Performance in Differently Tilled Soils in Auchi Area, Edo State of Nigeria

S Ojeniyi

The aim of study is to investigate soil properties and tillage requirement for yam on silty loam soils of derived savanna zone of Edo State, Nigeria and determine soil properties influencing yam performance Zero tillage (ZT), manual clearing (MC), mound (MD) and ridge (RG) were compared. The ZT gave highest values of soil organic matter, N, P, exchangeable K, Ca and Mg, at Auchi and Iyekhe, while MC had least values The ZT and MC had higher soil bulk density, moisture content, lower total porosity and temperature compared with MD and RG The MD and RG gave highest leaf N, P, K, Ca and Mg concentrations, sprouting percentage, number of leaves, leaf area, tuber weight and length. Differences in bulk density caused by tillage and non-tillage induced variation in yam growth, yield and nutrient status. The latter parameters were higher on MD and RG with lower bulk density values Mean tuber weights for ZT, MC, MD and RG were 23. 20, 112 and 12 3kg respectively Zero tillage and manual clearing cannot be substituted for mound and ridge in the study area.

Effect of Tillage and Mulch Combination on Soil Physical Properties and Sorghum Performance on Alfisol of Southwest Nigeria

S Ojeniyi

The effect of tillage method and mulching on selected soil physical properties and performance of sorghum (Sorghum bicolor) was studied in rainforest zone of South West Nigeria. Treatments were 4 x 2 factorial combination of tillage methods (zero tillage, manual clearing, heap, ridge), 12t/ha dry plant residue mulch, and no mulch. Mulch significantly reduced soil bulk density, temperature, increased moisture content and grain yield especially on heap and ridge compared with no tillage methpds. Ridge and heap increased shoot and root dry matter. Highest yield was recorded for ridge plus mulch, and heap plus mulch. Mulching of heap or ridge increased grain yield by 50%.

Keywords: Sorghum, growth, yield, soil, tillage, mu/ch.

Effect of Season and N Source on Brachiaria humidicola and Panicum maximum Growth Performance and Biological Nitrification Inhibition in Rhizoshepe soil

R Ipinmoroti

Two weeks old B. humidicola (CIAT 679) and P. maximum (CIAT 16028) seedlings were transplanted into 200 g portions of two Japanese soil types, viz, Andisol and Terrace yellow in cellophane pots with basal perforation covered with filter paper. The experiment included three N sources (100 ppm N03- as KN03, 100 ppm NH/ as [NH4hS04 and minus N), two plant types and control (B. humidicola, P. maximum and no plant) and the two soil types in a 3 x 3 x 2 factorial in a completely randomized design with 4 replicates in the greenhouse. The experiment was conducted in summer (June - August, 2007) and repeated in winter (November, 2007 - January, 2008). The plant shoots were harvested after three months of growth, weighed fresh, oven-dried, analyzed chemically and nutrient uptake determined. The roots in the potted soils were removed and 5 g equivalent dry weight of each were added to 0.6-mL mixing solution (120 mg N kg-1 soil) in 6 replicates, incubated at 30DC and N02-, NO-3 and NH4 - N contents determined at 1, 3, 7, 14, 28 and 56 days incubation. Data were analyzed by ANOVA at P~5%. The results showed that N supplied either as N03- or NH4 significantly (p~0.05) increased fresh (58.4 - 98.5%) and dry matter yields (62.6 - 100%) of the plants over the control in summer, with a similar trend in winter. Plant yields and nutrient uptake were significantly higher in summer than in winter. Nitrification was significantly reduced in B. humidicola rhizosphere soils than in P. maximum in summer but as high as or higher than P. maximum in winter due to slow growth and low activity status of exudates released. Nitrification was .greater in Andisol than Terrace yellow soil. It was concluded that season and inherent soil properties significantly influenced the growth performance of B. humidicola, nutrient uptake, root exudates release and their functioning in nitrification in soils.

Additional keywords: Animal nutrition, crop yield, forage quality, N loss, pasture grass, soil fertility.

An Appraisal of Fertilizer Subsidy in Developing Countries

V Asekunowo

Most developing countries’ fertilizer subsidy scheme is largely bureaucratically administered. Leakages occur causing unintended beneficiaries to benefit from the scheme while the intended beneficiaries are excluded. A cross-country survey of literature was carried out on fertilizer subsidy management in some selected developing countries. The survey largely revealed that fertilizer supply (availability) and demand improved in some developing countries that have made serious efforts at reforming their fertilizer supply and demand sectors; although some few observers hold dissenting views especially about the outcomes in the supply sector. Also, fertilizer supply and demand did not improve in the developing countries that did not make serious efforts at reforming these sectors. This suggests that the reform objectives of removing transaction costs and making fertilizers readily available to farmers at reduced prices seem to have been achieved in the reforming countries. The study therefore recommends that in order for the non-reforming countries’ farmers to be more accessible to fertilizers in sufficient quantities and at reduced prices, more serious efforts must be made at reforming these countries’ fertilizer supply and demand sectors. However, these reform efforts should be complemented with an institution of a workable output price support policy.

Keywords: fertilizer subsidy, leakages, fertilizer supply, fertilizer demand, shifting the fertilizer supply curve to the right (SSCR).

Effects of Cultivars and Rates of NPK (15-15-15) Fertilizer Application on the Growth, Development and Yield of Maize

A Adeyemi

The influence of maize (zea mays L.) cultivars and levels of NPK (15–15–15) fertilizer application was studied for two years at the Experimental Farm of the University of Ado-Ekiti, Ekiti State in the rainforest zone of South Western Nigeria. Commercial NPK (15–15–15) fertilizer was applied at 0, 250, 500 and 750kg/ha to DMRESR–Y, SUWAN–Y and DMRLSR–Y maize cultivars. Results showed that growth parameters and grain yield of maize were significantly influenced by maize cultivars and levels of NPK fertilizer. Height and growth of DMRLSR–Y were either superior or similar to that of SUWAN while DMRESR–Y gave least values of these parameters. Leaf area production and grain yield were highest in DMRLSR–Y followed by SUWAN and lowest in DMRESR–Y. Maize height, stem girth, leaf area production and grain yield of maize also increased with the increasing rates of NPK fertilizer.

Physical Properties of the Mountain Soils of Cross River State, Nigeria

A Essoka — 2010-09-02

The mountain soils of Cross River State, Oban hills and Obudu mountains have the following properties. The sand contents in Oban hills ranged from 34 to 82% while in Obudu plateau from 40 to 78 %. The silt contents of the soils in both Oban hills and Obudu plateau fluctuated with depth. At Oban hills the range was between 6 and 36 %, and 10 and 26 % at Obudu plateau. Clay contents at Oban hills ranged from 6 to 42 % while it ranged from 10 to 44 % at Obudu plateau. The bulk density values for both study sites increased with soil depth. The range of values at Oban hills top soils was 0.67 to 1.87 g/cm3, with the mean of 1.38 g/cm3 while values for subsoil horizon ranged from 1.64 to 2.33 g/cm3 with mean of 2.02 g/cm3.The range of bulk density values from the Obudu mountains was from 0.74 to 2.16 g/cm3. The soil surface values ranged from 0.74 to 1.75 g/cm3, with the mean of 1.2 g/cm. The total porosity values of Oban hills for top soil horizons ranged from 29.43 to 74.72%, with the mean of 47.93%. The subsurface horizon values ranged from 12.08 to 40.38%, with a mean of 22.54%. The surface soil horizon values at the Obudu mountains ranged between 33.96 and 70.08%, giving a mean of 50.63% while the subsurface values ranged from 19.62 to 55.47%, with the mean of 29.08%. Oban hills and Obudu mountain soils are rated good soils based on their total porosity values. The hydraulic conductivity values in the Oban hills ranged from 0.74 to 103.87 cm/hr. At the surface horizons, the conductivity values ranged from 7.56 to 103.87 cm/hr with the mean of 34.42 cm/hr. The subsurface horizon values ranged from 0.74 to 42.83 cm/hr, with the mean of 10.13 cm/hr. Hydraulic conductivity values at the Obudu mountains ranged from 0.05 to 78.99 cm/hr. The surface values ranged between 0.52 and 78.99 cm/hr, with the mean of 31.16 cm/hr. The subsurface horizon values range was from 0.05 to 42.13 cm/hr with the mean of 14.94 cm/hr. The conductivity values were high.

Keywords: Texture, hydraulic conductivity, bulk density, porosity.

Effect of Contact time on the Capacity of Adsorptive Materials for Metal Sorption in Solution

OI Nwachukwu

An experiment was carried out to determine metal sorption in solution, as a primary tool for evaluating metal immobilization as a viable option in the clean up of contaminated soil. Selected organic and inorganic materials were evaluated for adsorptive capacity as well as the contact time required for optimum sorption. Single solutions of Pb, Cu and Zn were prepared from metal salts and shaken with bone meal, general purpose compost, peat, coir, wood bark and green waste compost at controlled pH and laboratory temperature. Three metal concentrations of 0.1 mmol/l, 0.5 mmol/l and 1.5 mmol/l were used, at shaking times of 15, 30, 60 and 120, 720 and 1440 minutes. Sorption capacity of each adsorptive material was determined at equilibrium, and all six materials were effective in adsorbing the three metals. Contact time for optimal sorption was 1 hour, as more than 95% of metal sorption had occurred by 60 minutes of agitation.

Keywords: heavy metal, contact time, adsorption, sorption capacity

Effects of some Local Liming Materials and Organic Manure on some Soil Chemical Properties and Growth of Maize

D Asawalam

Experiments were carried out to find out the influence of some local liming materials, namely: woodash, flue dust and carbide waste and manure on soil pH, exchangeable acidity, exchangeable aluminium and yield of maize at Michael Okpara University of Agriculture, Umudike, Abia State Nigeria. The experiments consisted of laboratory and field studies. The results obtained showed that the different liming materials significantly increased soil pH relative to the control. On the average, it required 8.28, 2.3, 3.3 and 2.5 t/ ha of woodash, calcium hydroxide, flue dust and carbide waste, respectively, to raise soil pH from 4.8 to 5.5. Woodash and carbide waste applications reduced exchangeable acidity from 1.02 to 0.93, and 1.48 to 0.97 cmol kg-1 and raised soil pH from 4.51 to 5.18, and from 4.74 to 5.93, respectively. Maize height, girth, dry mater and grain yields as well as nutrient uptake were increased by increasing rates of organic manure. The best performance of maize in terms of growth, nutrient uptake, dry matter and grain yields were obtained with 20 t/ha organic manure application. The results of this study showed that liming materials enhance crop growth by reducing soil acidity while organic manure promote crop growth, nutrient uptake and yield.

Synergistic Effect of Poultry Manure and Sawdust on Changes in Soil Structural Indices of a Sandy-Clay Loam Ultisol

R Eneje

The effect of organic matter and exchangeable cations from admixture of poultry manure and sawdust incorporated into a field soil on soil structural indices of a tropical sandy clay loam soil was carried out. The aim was to investigate the level of amelioration of the poor structural attribute of the soil by balancing the cation and/or organic matter deficiency associated with the use of either saw dust (SD) or poultry manure (PM) alone in intensively cultivated soils in the tropics. The amendments SD, PM and PM + SD were applied at the rates 0t/ha, 2t/ha, 4t/ha and 8t/ha, making twelve treatment combinations with three replicates. Soil samples were collected for laboratory analysis at 4, 8 and 12 weeks. The structural indices analysed were aggregate stability (AS), dispersion ratio (DR), clay dispersion index (CDI), clay flocculation index (CFI) and aggregated silt and clay (ASC). Data were analysed using a 3 x 3 factorial in Randomized Complete Block Design (RBCD), significant means were detected using Fischer’s Least Significant difference (F – LSD) at 5% probability level. Data were also subjected to correlation analysis using Spearman’s Rank Correlation Coefficient. Result show that the treatments were statistically significant (P = 0.05) in affecting aggregate stability relative to the control. Decreases in bulk density occurred as a result of increase in amendment applied, the trend was 8t>4t>2t for all the amendments. However, only the application of 8t/ha of poultry manure decrease bulk density significantly (p = 0.05). The soil properties studied showed increased strength in the level of correlations with time, these correlations were highest at two months of sampling and was associated with the highest level of coefficient of determination, indicating that these properties influenced each other under the amendment condition and became intrinsic factors in determining the status of each other with increase in age of the soil. Specifically, effective cation exchange capacity (ECEC), and total exchangeable base (TEB) correlated negatively with ASC and CFI, but positively with CDI and DR for all sampling times.

Keywords: Aggregate stability, dispersion ratio, clay flocculation index, cation exchange

Algal Compost Effects on Soil Nutrient Status and Aggregate Stab

R Eneje

An experiment was conducted in the Soil Science laboratory of Micheal Okpara University of Agriculture Umudike, to investigate the effect of algal compost on soil nutrient status indices such as soil pH, cation exchange capacity, organic matter, total nitrogen and available phosphorus as well as soil structural stability. The experiment was a 3 X 3 factorial in a CRD and soil samples were collected from 0-20cm depth of a sandy loam soil from the University’s Western farm. The treatments applied were composts from combinations of alga and poultry manure (AC) and poultry manure alone (PM) and a control (C) with amendment rates of 0%, 10% and 20% respectively. Each treatment was replicated three times. Results show that the composted amendment influenced the soil nutrient status and structural stability at p< 0. 001. The influence on these properties increased as the rate of amendment and incubation time increased. The algal compost was more effective in improving soil structural stability, nutrient N content and cation exchange capacity of the sandy loam soil compared to the compost of poultry manure alone, while a compost from PM alone was more effective in improving the soil nutrient C and P as well as soil activity. There was a highly positive correlation between the soil structural stability index and soil nutrient status for the soil used in this study.

Key words: Algal compost, structural stability, soil activity, nutrient N, P, C

Fractionation and Distribution of Copper and Zinc in Calcareous Soils of Igarra, Nigeria

P Oviasogie

The experiment was conducted to fractionate Cu and Zn into the exchangeable, carbonate, Fe- Mn Oxide, organic and residual fractions within 0-30, 30-60 and 60-90 cm soil depths of calcareous soils of Igarra. The results obtained indicated that mean concentration of copper was highest in the Fe/Mn oxide fraction (3.68 mg kg-1) followed by the carbonate (1.93 mg kg-1) and exchangeable fractions (1.28 mg kg-1) respectively. Hence, the distribution trend of Cu in the various fractions was in the order Fe/Mn oxide > carbonate > residual > organic. On the other hand, the amount of Zn increased with depth in the exchangeable fraction with a relatively high concentration of 9.13 mg Kg-1. However, the highest amount of Zn (12.15 mg Kg-1) was obtained in the Fe/Mn oxide fraction. Zn occurrence in other fractions decreased in the following order: Fe/Mn oxide fraction > organic > carbonate > exchangeable. The present assessment of the forms and distribution of Cu and Zn in the soil showed that higher concentration of these metals in the Fe/Mn oxide fraction suggest unavailability or low supply of these metals for possible plant uptake in the short term.

Effect of Cassava Processing Effluent on Soil Properties, Growth and Yield of Maize (Zea mays L.) in South Eastern Nigeria.

F Ikpe

A study, comprising a survey, greenhouse and field experiments was conducted to examine the effect of Cassava Processing Effluent (CPE) on soil chemical properties, maize growth performances and grain yield. In the survey, soil samples were taken (0-15 and 15 – 30cm) of CPE contaminated and non contaminated areas of rural cassava processing depots. Serial dilutions of CPE collected from these depots (80, 60, 40, 20, and 0% (water only) were made and used to water potted maize plants for 30 days and field-sown maize for 120 days. The survey showed that soil pH, exchangeable potassium (K) and sodium (Na) were 4, 40 and 53% respectively, greater in uncontaminated than in contaminated soil. Calcium (Ca), Magnesium (Mg), available phosphorus (P) and organic matter increased significantly (p < 0.05) in CPE contaminated soil by 20, 9, 10 and 8%, respectively when compared with uncontaminated soil. Results of greenhouse and field experiments showed that all maize growth performances and grain yield were best when dilutions were between 20 and 40% (effluent in water). Mineralization of nitrogen (N) was greatly enhanced in the soil where CPE was disposed of when compared with NH4-N and NO3- N contents of uncontaminated soil. Since only traces of hydrogen cyanide (HCN) were analyzed in the soil at the end of the experiments (within recommended safe level of 5 mg kg-1) indicating that CPE is highly degradable.

Keywords: Cassava processing effluent, Soil properties, Hydrogen cyanide, growth, yield, maize, Southeastern Nigeria.

Evaluation of the Fertility Status and Suitability of some Soils for Arable Cropping In the Southern Guinea Savanna of Nigeria

M Adeboye

The study evaluated the fertility status and suitability of some soils for arable cropping in the newly established Teaching and Research Farm of the Federal University of Technology, Minna. Nigeria. Four soil units designated as 1, 2, 3, and 4 were identified through a rapid reconnaissance soil survey. A profile pit was dug to represent each of the soil units. Soil samples were collected from delineated horizons and taken to the laboratory for physical and chemical analysis. The Fertility Capability Classification (FCC) system was used to evaluate the soils for arable cropping. Results showed that argillic horizon was common to all the soils. The silt/clay ratio in the soils was greater than 0.20. Soils unit 1, 2, and 4 had inherent medium fertility status while Soil unit-3 had inherently poor fertility status. The FCC rated Soil unit - 1 as excellent for flooded rice cultivation. Ploughing, harrowing, ridging and field drainage to conduct standing water on the soil surface and in the subsoil will be required for successful cultivation of most arable crops in the soils due to their clay-textured subsoil. Soils unit -2 and 3 had low K level and will therefore need K fertilization especially for K- sensitive crops. Judicious use of inorganic fertilizer combined with organic manures is recommended for soil fertility maintenance for optimum and sustainable productivity of the soils.

Characterization and Classification of a Landscape underlain by Basement Complex for Engineering Purposes

G Akinbola

Utility of soil survey reports could be increased if used for evaluation of soils for engineering and other purposes apart from agriculture. The physical characteristics of some soils on basement complex in southwestern Nigeria generated from semi detailed soil survey activities were used for Urban Land Use Capability (ULUC) Evaluation. Soil morphological/physical characteristics, vegetation, land use, physiography, surface forms, stoniness and micro-relief of the soils were studied. Six soil series (mapping units) were identified and characterized on a 470.1 hectare land. Soil physical parameters evaluated for the ULUC include hydraulic conductivity, penetrometer resistance, bulk density, gravel content and particle size distribution. The soil characteristics and qualities that are of engineering importance like drainage, texture, structure, bulk density, consistency, gravel content, water holding capacity are important in grouping the soil for ULUC evaluation. Soil series identified were Iwo and Ibadan (Ferric Luvisol / Arenic Kandiustalf), Iregun (Haplic Lixisol / Typic Hapludalf), Balogun (Ferric Lixisol / Vetradic Hapludalf), Egbeda (Rhodic Ferrasol / Kanhaplic Rhodustalf) and Matako (Luvic Arenosol / Typic Psammaquent). Approximately 90 per cent of the entire area was rated ULUC class B for multipurpose / urban uses imposing slight physical constraints for development. Soil survey and evaluation maps and report can also be veritable tools for engineering and other agricultural uses.

Key words: Soil characteristics, Soil Engineering properties, soil series, soil survey.

Effect of Organic, Organomineral and NPK Fertilizer on Nutritional Quality of Amaranthus in Lagos, Nigeria.

S Ojeniyi

In Nigeria organic fertilizers are being developed from organic and farm wastes and these can be fortified with inorganic fertilizer. Therefore eight fertilizer treatments namely:(1) control (no fertilizer), (2) Pacesetter Grade B organic fertilizer (PGB) at 3 t/ha 100 %, (3) 300 kg/ha NPK fertilizer, (4) PGB + NPK fertilizer (75 : 25), (5) PGB + NPK (50: 50), (6)’ Kola pod husk (KPH) at 3t /ha 1 00%, (7) KPH +NPK (75: 25) and (8) KPH + NPK (50:50) were applied to amaranthus (Amaranthus cruentus). Residual effect on second and third crops was also studied. Proximate analysis was done to’determine crude protein (CP), crude fibre (CF), ash and ether extract (EE). The PGB and KPH alone or combined with reduced level. of NPK generally increased CP , ash and EE significantly on immediate and residual basis, the organic fertilizers had more residual effect than NPK . Organic materials alone or combined with NPK reduced CF especially on residual basis. Compared with organic materials, NPK gave least values of CP, ash, CF and EE. Application of KPH + NPK (50:50) , KPH and PGB gave highest values of CP and ash respectively. Integrated application of organic fertilizers and NPK gave highest values of EE in order: PGB + NPK (50:50), KPH (50:50), and PGB + NPK (75:25). Organic fertilizers and OMF maintain adequate CP and EE in first and second crops whereas NPK did not maintain adequate CP in second crop.

Response of Amaranth (Amaranthus hybridus) to Different Rates and Times of Urea Fertilizer Application

F Omolayo

The response of Amaranth (Amaranthus hybridus) to different rates and times of nitrogen (N) application was studied at Teaching and Research Farm,University of Ado-Ekiti in the late seasons of 2003 and 2004. The N was applied at 0, 50, 100 and 150 kg/ ha as urea (46%N) at 1, 2 and 3 weeks after sowing.Growth parameters and total yield were significantly influenced (P<0.05) by N rates and times of application. Plant height, stem girth, leaf number, leaf area and total yield increased with N level. The 50kg N/ha gave the highest values. Application of N at 3 weeks after sowing gave the highest values of growth parameters and yield.

Influence of NPK 20-10-10 Fertilizer on the Pod Yield and Root Growth of Okra in the Humid Tropics

O Awe

The influence of NPK 20-10-10 on the fresh pod yield and root growth of okra variety, V 35 grown in the lowland humid tropics was investigated during the 2002 and 2003 cropping seasons. Four rates (0,150, 300 and 450 kg/ha) of the fertilizer were applied to the crop. The treatments were replicated three times in a Randomized Complete Block design. The results showed significant differences (P=0.05) among treatment means for pod yield and dry root weight during the 2002 and 2003 trials. The root weight was positively correlated (r =0.99 and 0.96) to the fertilizer rates. The results suggest that the optimum NPK 20-10-10 level for okra variety, V 35 in the study area lies between 300-450 kg NPK 20-10-10/ha. Therefore, application rates above 450 kg NPK 20-10-10/ha for okra production in the study area will not be economical.

Characterization and Classification of Barikin Sale, Nigerian Southern Guinea Savanna Fadama Soils, for Sustainable Rice Production

I Onyekwere

Barikin sale Fadama soils in southern Guinea Savanna of Nigeria were studied regarding their properties, classification and management for sust non compacted with bulk density ranging from 1.37 to 1.72gcm-3, moderately acidic with a pH range of 5.1 to 6.3, have low ‘organic carbon, total nitrogen available P and basic cationic elements (Ca Mg K and Na). The soils were classified as Typic Haplustults (upper slope), Dystric Ustochrepts (middle, slope), aqUlc Ustochrepts (Hydromorphic fringe) and Typic Tropaquepts (bottom) and correlated with F AO / UNESCO soil map legend as Haplic Acrisols (upper slope) Dystric Cambisol (middle slope), and Gleyic Cambisols (Hydromorphic fringe and bottom).

Key Words: Fadama Soils, Characterization, Classification Management

Isolines of Rainfall Kinetic Energy and Intensity in Nigeira.

F Salako

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 lION, 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.