Animal manures and compost have been used since, earliest civilizations for
improving soil property. In years gone by these fertilizers were the only sources
of nutrient for crops production. Though, they contain relatively low concentrations
of nutrients and handing them is labour intensive, there has been largely increase
in their use over inorganic fertilizers as nutrient source on many farms (Kannan
et al., 2005). Their beneficial effects on soil physical properties
and the ease with which they decompose inside soil are major advantage they
have over inorganic fertilizers.
Their effects on soil is manifold, it can increase the nutrient availability;
alter chemical properties of the solid such as salinity, sodicity and pH (Alabadan
et al., 2009). They can also improve organic matter as well as physical
property of the soil such as bulk density, aggregate stability, aggregation,
crust strength and water infiltration (Zeidan, 2007).
Allowing manure to flow into surface water can give rise to pollution, time
has therefore come when one must worry about the impact of organic manure on
the soil and crop production and also its effect on the environment and humans
health. Considerations such as appropriate rate, timing and method of application
and expected crop response are important when using manure as a source of plant
nutrient. Crop may suffer from deficiency and injury as a result of under application
and over application, respectively both leading to reduced yield (Saleh
et al., 2003).
Cowpea (Vigna unguiculata) is a legume grown in savannah region, the
tropics and sub-tropics. It is largely grown in West and Central African countries.
It value lies with high protein content, its ability to tolerate drought and
the fact that it fixes atmospheric nitrogen if allowed to grow on a poor soil
(Akinyele et al., 1986). The ability of cowpea
plant to tolerate drought and poor soil makes it an important crop in the savannah
region where these constraints restrict other crops. Its grain is nutritious
and is a cheap source of protein for both rural and urban consumers. Its grain
contains about 25% protein and 64% carbohydrate, it is also a genuine African
crop for hay and forage production (Chinma et al.,
The 1st step in good management of any product is to understand the nature
of the material. A practical approach to poultry manure handling is to characterize
the waste material before it can be appropriately used as soil amendment because
variation is introduced by differences in species of animal used, housing systems
and age even within a specific operation, the characteristics of the manure
will be influenced greatly by the ration, the type of bedding and the handling
system (Zeidan, 2007). Cattle manure is a combination
of faeces, bedding material, wasted feed and water. It has high organic matter
content. The organic fraction of manure plays an important role in increasing
soil organic matter and tilth, improving soil structure and soil infiltration
capacity (Reyhan and Amiraslani, 2006). Many of the
nutrients in the manure, however are tied up in the organic fraction and must
go through a decomposition process to be converted to the inorganic forms available
for plant uptake (Kannan and Saravanan, 2006). Getting
the maximum value out of cattle manure requires applying the manure at proper
rates and frequency. Over application can lead to transport of nutrients into
the groundwater through leaching or overland flow and can also lead to losses
of ammonia and nitrous oxide into the atmosphere (Gerard
et al., 1982).
Several studies have been conducted to know the negative impact of organic
fertilizer on soil; Reyhan and Amiraslani (2006) stated
that the applications of cattle feedlot manure at the rate of 90 mg/ha/year
increased the electrical conductivity of a soil in southern Alberta by about
6 dS m-1 and the sodium adsorption ratio by about 3 mol dm-1.
Kannan and Saravanan (2006) reported that repeated annual
applications of manure which has high salt content caused a build-up of soluble
salts in the soils to the extent of lowering crop productivity. Also, Assefa
reported that four annual applications of solid dairy manure at an average rate
of 158 Mg ha-1 reduced the yield of Sudan grass due to salinity.
In a study that was conducted in the Peace river region of Alberta, single manure
application to soils at rates as high as 176 kL ha-1 of hog or 185
Mg ha-1 of cattle manure did not pose any significant problem of
salinity. In the same study in Central Africa, however four annual applications
of cattle manure at the rate of 15 Mg ha-1 increased the salinity
(EC) of the soil from 0.3 dS m-1 to 1.6 dS m-1 and increased
the sodicity (Sodium Adsorption Ratio, SAR) from 0.7-1.7 (Saleh
et al., 2003).
An application of manure at 40 g kg-1 of soil increased the pH from
4.8-6 and from 5.5-6.3 for fresh or composted animal manure applications. Ramadan
and Adam (2007) then suggested that the increase in pH of an acid soil following
manure addition was only partially due to buffering from bicarbonates since
they did not detect carbonate in either the manure or soils examined in their
study. They proposed that compounds other than carbonates and bicarbonates such
as organic acids with carboxyl and phenolic hydroxyl groups have important roles
in buffering soil acidity and increasing the pH of acid soils amended with manure.
Their conclusion was that the effects of manure on soil pH would depend on the
manure source and soil characteristics. Manure has been recognized throughout
recorded history as an excellent soil amendment that can be used as organic
fertilizer however, they are also known to have negative effects on soil if
not handled appropriately and therefore study needs to be conducted to ascertain
the extent of positive and negative effect of this cheap but important resource.
The objectives of this study are therefore to evaluate the effect of poultry
and cattle manure on cowpea production and to evaluate the salinity effect of
the two organic manures on the soil under cultivation.
MATERIALS AND METHODS
The experiment was conducted on a 10x20 m plot along London street in Chanchaga
local government area of Niger state. The site lies on latitude 09°30' and
longitude 06°32' (Chukwu et al., 2008) with
the average annual rainfall of 1287.4 mm. Soil samples were taken from the selected
site and taken to laboratory for physical properties and textural class determination.
Eight 10x2 m ridges were then made on the plot. The study is aimed at investigating
the effect of cattle and poultry manures either used alone or combined together
on its soil amendment effect and the yield of cowpea using the same application
ratio. Therefore, cattle manure was obtained from local cattle farm at Gbeganu
village in the same local government.
The poultry manure was collected from the rearing section of a local poultry farm where the birds were under 16 weeks old and kept under deep litre system on floors with sawdust. The manures were weighed and 10 kg each of poultry and cattle manure were applied to the cultivated ridge one to four, respectively. Ridge five and six were treated with a mixture of poultry and cattle manure mixed at equal proportions while the last ridge seven and eight were left untreated to serve as control. The applied manure was allowed to mix well with the soil by light irrigation with portable sprinkler system once daily for 3 days. TVx3236 cowpea variety was then planted at the rate of three seeds per stand at 45 cm intra-row spacing. The treatments with manure were done at 2 weeks interval three times after the establishment of the crops.
Plant parameters measurement: The plant parameters measured were the
Heights (H), Stem Girth (SG) and Leaf Area Index (LAI). Plant height was measured
using a meter rule while the leaf area (cm2) calculated as the product
of the total length and breadth at the broadest point of the longest leaf on
the plant. Stem girth (cm) was measured with vernier caliper. This was done
four times at 2 weeks interval during the growing period of the crop.
where, n is number of ridges. Physicochemical parameters of the soil samples were also analyzed before and after the application of the manure. After fruiting, some harvested pod were also taken randomly and assessed for parameters needed to calculate the yield like number of pod per stand and number of grain per pod to ascertain whether the applied manure has any effect on the yield of the cowpea variety.
RESULTS AND DISCUSSION
The results of all the parameters measured are showed in Table 1. Both manures have significant effects on both the soil properties and growth parameters of the cowpea variety used. From Table 1, the average bulk density of the soil is calculated to be 1.50 g cm-3. From the textural class determination using sieve analysis method, it was observed that the soil is sandy loam with 55% sand, 26% clay and 19% silt. From Table 2, there was a remarkable increase in all the growth parameters for all the treatments over the control.
All the growth parameters were affected by manure application. Also, poultry
manure alone led to remarkable difference in height, leaf and stem diameter
while combination of poultry and cattle manures (p+c) gave better leaf area
compared to the use of either of the manures alone. The improvement in crop
parameters is associated with increase nitrogen, phosphorus and potassium levels
in the soil as affirmed by Reyhan and Amiraslani (2006).
Table 3 shows that the plot treated with poultry waste has
the highest yield followed by that of a mixture of poultry and cattle manure.
One will expect the plot treated with cattle manure to yield more than the control
plot but converse is the case. This is in line with the findings of Reyhan
and Amiraslani (2006) that the efficiency of cowpea is high but may be inhibited
by the application of cattle manure. It may also be traced to the salinity effect
which if too high in cattle manure may affect the yield considerably.
|| Bulk density determination
|| Average plant parameters 6 weeks of manure application
|a-cLetters inside the parentheses indicate 2, 4
and 6 weeks after planting, respectively
|| Average yield from the plot
Table 4 shows that application of organic manures has a significantly
effect on soil chemical characteristics. Porosity increased from 0.47 for control
plot to 0.88 for plot treated with a combination of poultry and cattle manure.
This might be partly due to Obi and Ebos findings that application of
organic manure enhances the promotion of biological activity which in turn increases
the organic matter content of soil. The pH value increased for all the three
treatment with combination poultry and cattle manure having highest of 8.2 as
against 6.4 on the control plot. This may be due to the increase in availability
of P and K in the soil. This may also be in line with the findings of Dewi that
plots treated with poultry manure do have increase in the carbonate content
due to availability of calcium containing materials in poultry feeds.
Health impacts: The 1st health impact associated with the used of animal
manure is bad odour from the manure especially poultry manure. Others include
the danger of zoonosis and tendency of contacting skin diseases if the person
applying is not properly protected.
|| Average physicochemical parameters of the soil
Protection of skin and other part of the body for the person applying the manure
is recommended and can be achieved by using hand gloves and other protective
wears like nose guard to reduce the health impact while working on the farm.
The result of this study has buttressed earlier findings that organic manure in general can provide the necessary nutrients needed by plants for growth. The study also showed that both poultry and cattle manure can provide the fertilizer requirements of cowpea either when applied alone or combined together. Meanwhile, the physical parameters of cowpea on the plot treated with poultry and cattle manure did not give progressive increment in parameters with respect to increasing application rate as some findings have shown, this might be due to accumulation of some chemicals present in the manure that may eventually render the soil saline and thereby reduces crop productivity.
For future improvement on this research, it is recommended that mechanical device should be used in the application of both manure and seed in further studies. Government should also encourage the use of organic fertilizers for their farming activities and a proper method of analyzing the amount of animal manure needed for a particular plot to avoid under or over application problems on fields.