Status and Distribution of some Available Micronutrients in the Haplic Usterts of Akko Local Government Area, Gombe State, Nigeria
This study has been conducted to assess the status and distribution of available Zinc (Zn), Copper (Cu), Iron (Fe) and Manganese (Mn) in soils of Akko Local Government Area (LGA), Gombe State, Nigeria. Sixty composite soil samples were collected from 0-15 and 15-30 cm depths from 15 purposively selected representative locations in the LGA and analyzed in the laboratory using standard procedures. Results obtained showed that the soils were generally clayey to sandy clay loams, slightly to moderately acid (pH range = 5.77 -6.5; mean = 6.1), low in organic carbon (mean = 0.83 g kg-1) and low to medium in exchangeable bases. Zinc was generally low in all the locations (range = 0.13 to 0.37; mean = 0.22 mg kg-1), Cu ranged from low (66.7%) to medium (33.3%) while Fe (mean = 10.80 mg kg-1) and Mn (mean = 34.0 mg kg-1) were generally high in content. Depth significantly (p<0.05) influenced the distribution of all the micronutrients studied except Fe that did not significantly vary with depth. For sustainable crop production, it is recommended that the pH be improved to near neutral. Crops grown in all the locations will benefit from Zn and organic matter application while areas identified low for Cu should have Cu included in their fertilization programme.
Received: February 03, 2011;
Accepted: April 30, 2011;
Published: July 12, 2011
Micronutrients are metallic chemical elements necessary for plant growth
in only extremely small amounts. Although required in minute quantities however,
micronutrients have the same agronomic importance as macronutrients and play
vital roles in the growth of plants (Nazif et al.,
2006). These metallic chemical elements include Zinc (Zn), Iron (Fe), Copper
(Cu) and Manganese (Mn), amongst others. Most micronutrients are associated
with the enzymatic systems of plants. For instance, Zn is known to promote the
formation of growth hormones, starch and seed development, Fe is important in
chlorophyll formation, Cu in photosynthesis and Mn activates a number of important
enzymes and is important in photosynthesis and metabolism (FFTC,
The origin and sources of micronutrients in soils are as diverse as they are
variant. However, the major sources include: parent materials, sewage sludge,
town refuse, farm yard manure and organic matter (Nazif
et al., 2006). It is reported (Brady and Weil,
2005) that Fe and Mn are common in silicate minerals such as biotite and
horneblende. Zinc may also replace some of the major constituents of silicate
minerals including clays and be found therein, while Cu and Mn are often tightly
held by organic matter.
In Nigeria, micronutrient deficiencies were quiet rare, owing in part to the
extensive system of agriculture practiced that permitted the recuperation of
soils over a fairly long period of fallow. This tended to replenish the soil
macro- and micro-nutrients that were hitherto lost. However, with the increasing
human and animal population in Nigeria in general and in Gombe State in particular
and the countrys drive to attain food security, the abandonment of the
traditional extensive agricultural system, to a more scientific intensive one
has become imperative. This, coupled with the use of new high yielding crop
varieties which are nutrient demanding and the realization of the concept of
balanced nutrition by farmers have unraveled micronutrient deficiencies in some
Nigeria Savanna soils (Mustapha and Loks, 2005).
As a pre-requisite to the successful implementation of the scientific agricultural
practice, the evaluation of the nutrient status of the soils, including the
micronutrients becomes necessary. This will ensure a more economic utilization
of the soil resources by the resource-poor Nigeria farmers (Mustapha,
2003) and also help in the Governments drive towards food sufficiency.
With this view this study was undertaken with the objective of determining the status and distribution of available zinc, copper, iron and manganese, in the cultivated Haplic usterts of Akko LGA, Gombe State, Nigeria as a case study for soils with similar characteristics in other agro-ecologies.
MATERIALS AND METHODS
The study area: The study was conducted between May and August, 2010
in Akko LGA; located along Gombe-Adamawa road, about 30 km away from Gombe town.
It is situated 12°30N and 11°45E, within the northern Guinea
Savanna Zone of Nigeria. The geology of the area is said to be of tertiary continental
sandstone to the west of the Keri-Keri escarpment, clays and siltstones. The
climate is characterized by two distinct wet (May to October) and dry April)
seasons. The annual rainfall is about 800 to 900 mm per annum with mean annual
temperature ranging from 30° to 32°C (BSADP, 1982).
Soil sampling and handling: A total of 60 composite soil samples were collected at 0-15 and 15-30 cm depths from 15 different, purposively selected representative locations in Akko LGA of Gombe State, Nigeria. Each composite soil sample was made of five sub-samples.
The collected soil samples were properly labeled and stored in polythene bags and taken to the laboratory. In the laboratory, each sample was separately dried in air and then ground using porcelain pestle and mortar. The ground soil samples were sieved with 2 mm sieve and the fine earth fractions, collected in separate bags, were used for all the laboratory analyses.
Laboratory analyses: The processed soil samples were analyzed for some
physico-chemical properties including the micronutrients (Zn, Cu, Fe and Mn)
under investigation following procedures described by Page et
al. (1982). Particle size distribution was determined by the hydrometer
method after dispersing in sodium hexametaphosphate solution (Bouyoucos,
1951). The soil pH was determined in 1:1 soil/water suspension using a glass
electrode pH meter while organic carbon in the soil was determined by the wet
combustion method of Walkley and Black (1934). Cation
exchange capacity was estimated using the NH4O Ac saturation (pH
7) method, while the leachate was used to determine the exchangeable bases.
The extractable micronutrients: Zn, Cu, Fe and Mn were extracted with 0.1M HCl
solution (Osiname et al., 1973) and determined
on an atomic absorption spectrophotometer at appropriate wave lengths.
For the purpose of micronutrient fertility ratings, the limits given by Esu
(1991) were employed. For Zn, values <0.8, 0.81-2.0 and >2.0 mg kg-1
were respectively rated low, medium and high
while for Cu, the respective fertility category rating limits were <0. 2,
0.21-2.0 and >2.0 mg kg-1. Iron was regarded as low
if <2.5, medium if 2.51-5.0 and high if >5.0 mg
kg-1. Manganese was low if the values were <1.0, medium
if 1.1-5.0 and high if >5.0 mg kg-1.
Data analysis: Data generated were subjected to simple descriptive statistics,
including range and means (Harry and Steven, 1995). Computer
Minitab software was employed for analysis of variance to determine significant
differences between means. Means that were statistically different were separated
using the Least Significant Difference (LSD).
RESULTS AND DISCUSSION
Physico-chemical properties: Results of some physico-chemical properties
of the soils studied are presented in Tables 1 and 2.
The particle size distribution of the soils as shown in Table
1 indicates that the soils have relatively high sand (mean = 46.9%) and
clay (mean = 30.1%) contents; giving the soils a generally sandy clay to clay
texture. Clay content significantly (p<0.05) increased with soil depth. This
is expected as some of the increase with depth in clay may be as a result of
removal of the fraction by surface run-off and also by illuviation. This is
a common phenomenon in soil in this agro-ecology as was also reported by Voncir
et al. (2008).
|| Particle size distribution in the Black cotton soils
in Akko LGA, Gombe state, Nigeria
|NS: Not significant
|| Exchangeable bases (in cmol(+)kg-1) of some soils
in Akko LGA, Gombe State, Nigeria
|NS: Not significant
The results also indicate that all the fractions varied significantly (p<0.05)
between the locations indicating wide variability in the fractions between soils
from different parts of the LGA. Except for clay, however, all the other fractions
did not vary significantly (p>0.05) with depth probably indicating the importance
of illuviation as a pedogenic process in this area as also reported by Uzoije
and Onunkwo (2011) elsewhere in south-eastern Nigeria.
The soil reaction ranged from pH 5.7-6.5 (mean = 6.1) indicating slightly to
moderately acidic reaction. Though generally acidic, the pH values varied significantly
(p<0.05) between the locations and depths considered. The upper 0-15 cm was
more acidic (pH = 5.8, moderately acidic) than the lower 15-30 cm (pH = 6.4,
slightly acidic). This could be attributed to the removal of basic cations from
the surface of the soils to the lower depths (Mustapha and
Loks, 2005; Voncir et al., 2008; Kolo
et al., 2009) and/or the use of acid-forming fertilizers such as
urea for agricultural purposes.
Results in Table 1 show that organic carbon content ranged
from low to medium (Esu, 1991) across the locations; with
values ranging from 0.12 to 1.56 (mean = 0.83) g kg-1. Even though
the surface 0-15 cm soils contained more organic carbon (0.99 g kg-1)
than the lower 15-30 cm (0.75 kg-1), the differences were not statistically
significant (p>0.05). Similar low organic carbon values have been reported
by Yaro et al. (2006) for the Nigeria Savannah
soils, Mustapha and Nnalee (2007) and Mustapha
et al. (2007) for soils in the northern guinea Savanna zone of Nigeria.
The exchangeable bases (Ca, Mg, K and Na), except for Na, did not significantly
(p<0.05) vary with location and depth (except for K) (Table
2). The Ca varied from medium to high (range = 3.7-7.2; mean = 5.1 mg kg-1),
Mg (range = 0.33-0.72; mean = 0.53 mg kg-1) was medium, while K (range
= 0.01-0.66; mean = 0.27 mg kg-1) and Na (range = 0.01-0.05; mean
= 0.02 mg kg-1) were low to high and low, respectively.
|| Some exchangeable micronutrients (in mg kg-1)
of some soils in Akko LGA, Gombe State, Nigeria
|NS: Not significant
Zinc status: Results in Table 3 show that Zn in the
soils studied ranged from 0.13 to 0.37 (mean = 0.22) mg kg-1 between
the locations; placing it in the low category. This indicates that
soils in all the locations studied were deficient in the nutrient as the values
were below the critical 0.80 mg kg-1 reported by Esu
(1991). Except for some locations such as L. Mango (0.13 mg kg-1),
Gamawa (0.37 mg kg-1) and Y. Shehu (0.32 mg kg-1), Zn
was fairly uniformly distributed in the area studied. The values obtained in
the present study are indeed lower than the 0.48-0.75 (mean = 0.58) mg kg-1
obtained for the soils elsewhere in the State (Mustapha
et al., 2010).
Depth significantly (p<0.001) influenced the distribution of zinc in the
soils studied. Soils from the top 0-15cm contained significantly (p<0.05)
more (0.27 mg kg-1) Zn than soils from the lower 15-30cm (0.17 mg
kg-1). The implication here is that plants may not have a Zn store
in the lower soil strata which plants could exploit especially if same obtains
even at lower depths. Similar decrease with depth was also observed by Mari
et al. (2006) in soils in Pakistan.
Copper status: Table 3 shows that Cu in the soils
studied ranged from 0.09 to 0.28 (mean = 0.18) mg kg-1, putting it
in the low to medium fertility rating. These results
obtained are lower than the results obtained by Mustapha
and Singh (2003) for soils elsewhere in Galambi, Bauchi State, Nigeria in
similar agro-ecology but are similar to the 0.81 to 0.26 (mean = 0.21) mg kg-1
obtained by Mustapha et al. (2010) in other area
in Gombe State. It is pertinent to note that Cu significantly (p<0.05) varied
with locations. Most (66.7%) of the soils studied were classed low
in Cu fertility while about 33.3% were in the medium category. Consequently,
crops grown on most of the soils in the LGA will benefit from supplementary
Between the depths considered, Cu varied rather significantly (p<0.05). The upper 0-15 cm contained significantly higher (0.22 mg kg-1) amounts of Cu than the lower 15-30 cm (0.13 mg kg-1). This indicates that while the upper soils contain sufficient amounts of Cu for crop production, the lower soils may not serve as a reservoir for replenishing lost Cu taken up by plants and/lost through other means.
Iron status: Iron contents in the soils studied ranged from as low as
5.7 at W. Yola to a high of 14.9 mg kg-1 at Gamawa (Table
3). Even though the soils contained Fe above the critical 2.5 mg kg-1
given by Esu (1991), the values recorded for the soils
(mean = 10.80 mg kg-1) are below those recorded (range = 18.40-21.91;
mean = 19.96 mg kg-1) for soils elsewhere in Gombe State, Nigeria
(Mustapha et al., 2010) and the 12.40-45.10 mg
kg-1 reported for Ustults in the neighbouring Bauchi State, Nigeria
(Mustapha and Singh, 2003).
The contents indicate that with values above the critical limits for crop production,
Fe deficiency is very unlikely for any crop grown on these soils. This is especially
so when viewed against the backdrop of reports (Mengel and
Geurtzen, 1986) that Fe deficiency is very unlikely in acid soils; as it
is known to be soluble under relatively acid and reducing conditions (Chesworth,
Although there was an apparent increase in the Fe content with depth from 9.9 in the 0-15 cm depth to 11.8 mg kg-1 in soils within 15-30 cm, the increase was not statistically significant (p<0.05).
Manganese status: Manganese in the soils (Table 3)
according to the ratings by Esu (1991), was high
ranging from 25.9 to 43.7 (mean = 34.0) mg kg-1. These values suggest
that the soils contain sufficient Mn for successful agriculture in the area
studied as they are above the critical limits of 3-5 mg kg-1 reported
by Lindsay and Norvell (1978) and 1-5 mg kg-1
reported by Esu (1991). The values obtained are higher
than the 7.89-12.00; mean = 9.10 mg kg-1 obtained by Mustapha
(2003) for the Ustults in Bauchi State, Nigeria.
It is pertinent to note that Mn distribution was significantly (p<0.05)
influenced by depth with the lower 15-30 cm depths containing significantly
more (40.40 mg kg-1) Mn than the upper 0-15 cm (27.60 mg kg-1).
The high Mn contents may not be unconnected to the acidic nature of the soils.
Sillanpaa (1982) reported that above soil pH of 7.5,
the availability of Mn is very low because of the formation of hydroxides and
chelates. Worthy of note is that the high contents of Fe and Mn in the soils
studied could lead to the formation of complexes which could lead to serious
drainage and infiltration problems.
Results from the present study indicate that the soils were generally clays to sandy clay loams in texture, slightly to moderately acidic (5.7-6.5) and low in organic carbon (matter) with low to medium contents of exchangeable bases. Zinc was generally low in all the locations while Cu content ranged from low to medium with about 66.7 and 33.3% of the soils falling in the low and medium categories, respectively. Equally worthy of note is that the soils contained Fe and Mn above the critical limits for crop production and categorized high. This, may be a potential environmental problem as they may, upon complex reactions, result in the formation of plinthites and petroplinthites leading to hard pan formation; restricting rooting depth and causing infiltration and drainage problems in the soil.
Owing to the aforementioned observations, it is recommended that for successful crop production in the area studied; concerted efforts should be geared towards improving the pH to near neutral especially for locations at Wuro Yola, Kembu, Gamawa and Wuro Abba. Application of organic matter to improve the overall fertility of the soil and to reduce the possible development of plinthic/petroplinthic layers is further recommended. Crops grown in all the locations will benefit from Zn and organic matter application while areas identified low for Cu should have Cu included in their fertilization programme.
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