Incubation of Selected Tanzanian Chromic Acrisol with Minjingu Mazao Fertilizer, Cattle and Poultry Manures and Their Effects on Phosphorus Availability
This study investigated effects of incubation period on Phosphorus (P) release from selected P-sources. The latter are reported to improve levels of P in highly weathered Chromic Acrisol, which has been under continuous cultivation. The study was based on screen-house which utilized Minjingu Mazao (MM) fertilizer, Cattle (CM) and Poultry (PM) manures. The MM fertilizer was applied at 0.258 g per 4 kg soil, equivalent to 40 kg P ha-1. Cattle manure and PM were incorporated in soils with and without MM at 10 g per 4 kg soil. The incubation went through 14, 28 and 42 days and P was analyzed after every incubation period. Results showed that incubating the soil with deionized water for 14 days adjusted P from 7.9 to 8.4 mg kg-1 soil. The MM, PM and CM increased P to 12.2, 15.9 and 17.9 mg kg-1, respectively. In addition, MM+CM, MM+PM increased P to 16.1 and 14.2 mg kg-1, respectively. Initially, P increased significantly (p <0.001) but later decreased substantially beyond 14 days. However, PM and CM gave relatively promising P values between 14 and 28 days as opposed to 42 days of incubation. It was concluded that incubating cattle manure and incorporating it with Minjingu Mazao fertilizer provides promising P quantities indicating high rates of P depletion in soils. Incubating soil with poultry manure and incorporating Minjingu Mazao fertilizer had slow release of P hence, might benefit a slow growing crop.
Received: September 02, 2013;
Accepted: January 03, 2014;
Published: March 06, 2014
Soil fertility depletion is a fundamental biophysical factor that accounts
for the declining agricultural production in Sub-Saharan Africa (SSA), Tanzania
inclusive (Kisetu and Teveli, 2013). Unstable agricultural
production and low per capita income in developing countries reinforce decline
in soil fertility as land degradation and water resources also reduce the capacity
of smallholder farmers to invest in sustainable soil fertility management (Shiferaw
et al., 2009). There has since long been a contradiction that fertilizer
use and adoption of this practice in SSA is low besides high return to fertilizer
use and high levels of land degradation and nutrient mining related to continuous
agricultural activities (Vondolia, 2011).
Phosphorus (P) deficiency problems are common in highly weathered Chromic Acrisols
(Ferralsols) and young soils (Andisols) because of their strong acidic and/or
alkaline reactions, respectively and abundance of Al and Fe ions (Saleque
et al., 2004), which are the acid forming cations (Kisetu
and Teveli, 2013). Phosphorus retention by these agricultural potential
soils (Msanya et al., 2003), is also influenced
by Fe and Al oxides (Hakim, 2002), exchangeable calcium
(Ca) and Magnesium (Mg), soil texture, porosity, ionic strength and hydraulic
conductivity (Del Bubba et al., 2003) and land
utilization types (Amapu et al., 2000). Mans
land use activities affect global P-cycle and if P is applied to soils in excess
of crop requirement, P will generally build up in the soil (Zhang
et al., 2005) and this would increase the chances of P losses in
soil system through leaching, percolation and/or formation of complex compounds
in soil suspensions (Sharpley et al., 1999).
Ferralsols are among the major red soils dominating the humid and sub-humid
tropics of Africa (Deckers, 1993) and are characterized
by low total and available P contents attributed to high P retention capacities
(Friesen et al., 1997). Most of these soils
have subsurface horizons (fragipans) with hardened accumulations of Fe oxides-haematite
(Fe2O3) or hydroxides-goethite (FeO(OH)) and limonite
(FeO(OH).n(H2O)) mixed with other minerals such as plinthite and
ironstone (Shaw, 2006), constituents which hamper availability
of P for plant uptake. Low quantities of soluble P in soil limit crop production
(Moazed et al., 2010). Crop response to P applications
to P deficient soils have been highly erratic and below expectations, using
various plant growth models, a phenomenon which has been attributed to the P-adsorption
capacities and other transformations in soils (Kisetu and
Teveli, 2013). According to Heerink et al. (2001),
a need to restore and preserve sustainability of agriculture and safeguard the
livelihood of large segments of rural population should be urgent to rebuild
soil fertility using locally available nutrient sources, improve and sustain
current levels of productivity and farm income.
There have been low rates of fertilizer consumption in developing countries,
hence retarding economic adjustment through agricultural sector. According to
Morris et al. (2007), fertilizers use intensity
in Africa was 8 kg ha-1 in the year 2000 as compared to 96 kg ha-1
for East and Southeast Asia and 101 kg ha-1 for South Asia and Netherlands
usage was 400 kg ha-1. The explanation for this normally ranges from
fertilizer marketing system imperfections to systematic biases in dynamic decisions,
a situation which has contributed to low food reserves in community thereby
increasing hunger in the area concerned (Kisetu and Teveli,
2013). A study by Banful (2009) holds that past efforts
to promote use of fertilizer as soil amendments in agricultural potential parts
of Africa were too narrow and only concentrated on stimulating increase in fertilizer
use without crowding in other complementary inputs such as investment in feasible
organic materials on soil and water conservation. Phosphorus is an essential
plant nutrient and its deficiency in soils severely affects crop yields (Brady
and Weil, 2008).
Depending on its geologic origin, Phosphate Rock (PR) has widely varying mineralogy,
texture and chemical properties. Some PR exists as hard-rock deposits, while
other exists as soft colloidal (soil-like) PR material (Msolla
et al., 2005). The existing high variation in the nutrients
status or elemental compositions and the overall potentials of Phosphate Rocks
greatly influences their market and crop values.
The general reaction of PR dissolution added to soils to a plant available
Low soil Ca concentrations and high Cation Exchange Capacity (CEC) favour PR
dissolution since Ca is one of the reaction products resulting from PR dissolution.
A study conducted by Tengerdy and Szakacs (2003) showed
that soil conditions that limit Ca availability (soil acidity, high leaching,
or presence of organic compounds that complex exchangeable Ca) also favour PR
dissolution and release of P. In addition, Akande et
al. (2004) emphasized that among the cultural practices that may improve
P availability from PR include broadcast applications to maximize soil dissolution
reactions and using managements that promote root colonization by mycorrhizal
fungi. However, Zapata (2002) insisted that an application
of PR should be made several weeks or months prior to anticipated need for plant
nutrients. Akande et al. (2005) also reported
that although lime applications are important for reducing harmful effects associated
with soil acidity, lime additions tend to reduce the value of PR as a source
Soil moisture and pH are among the important attributes in the dissolution
of Phosphate Rock (PR) (Zapata, 2002). The PR is much
more soluble in acidic soils (pH<5.5) but several local and technical approaches
have been used to promote and increase P availability in PR including: (1) Incorporation
of additives into PR, (2) Partial acidulation of PR, (3) Compaction of PR with
water-soluble P fertilizers and (4) Microbial dissolution methods (Straaten,
2002). Composting manure and/or biological wastes with PR has since long
been shown to enhance dissolution of the PR and is practiced widely as a low-input
technology to improve the fertilizer P value of manure (Mahimairaja
et al., 1995). However, there is little information available on
feasibility of this technology with Minjingu-Mazao fertilizer which is of PR
origin in enhancing P availability under Tanzanian soils (Ikerra
et al., 2006). In addition, there are no studies that have critically
been conducted to investigate influence of cattle and poultry manures on release
of nutrient P under different soil amendments. These knowledge gaps necessitated
the need for this study which determines quantities of P released from Minjingu
Mazao (31% P2O5 carrying 13% P) fertilizer applied at
a rate equivalent to 40 kg P ha-1 checked with cattle and poultry
manures. Therefore, this study determined effects of incubating soil with M-Mazao
fertilizer, cattle and poultry manures to P released.
In addition, it determined the relationship between P-sources incubated and
MATERIALS AND METHODS
Experimental site and acquisition of the experimental materials: The
study involved laboratory pot-incubation experiment which was conducted at the
Sokoine University of Agriculture (SUA). Fresh organic manures (cattle and poultry)
were collected from Magadu Livestock Farm hosted by the Department of Animal
Science and Production at SUA, whereas the Minjingu Mazao fertilizer was obtained
from fertilizers stock in the Department of Soil Science at SUA. The bulky soil
Chromic Acrisol for composting Minjingu Mazao fertilizer and organic manures
was collected from SUA Farm, section of the Department of Soil Science located
between latitude 07°25 South and longitude 38°04 East and
at an elevation of 540 m above mean sea level (amsl). The soil is characteristically
kaolinitic receiving annual rainfall between 800 and 950 mm lasting from November
to January and the second season (long rains) lasting from February to May (Hatibu
et al., 2003).
Decomposing organic manures and setting of incubation experiment: Fresh
organic manures (cattle and poultry) were decomposed exclusively in limited
supply of oxygen for 14 days into humus by regular moistening with tap-water
to 30% moisture content along with monitoring temperature changes in the decomposing
containers. Thereafter, organic manure compost was left to cool under shade
for 12 h and a small amount of each type of manure was packed in small bags
for lab moisture content determination. Thereafter, the composts were incorporated
into 4 kg 8 mm sieved soil in 5 L capacity plastic containers. Three pots were
kept as absolute control in which its soils were not incorporated with M-Mazao
fertilizer or organic composts. In the pots while considering the amount of
moisture content, 10 g of manure compost was incorporated with 0.258 g of 31%
P2O5 Minjingu Mazao fertilizer into 4 kg soil in a pot
(equivalent to 5 t ha-1 manure and 40 kg P ha-1 of MM
fertilizer). The treatments were such that: S = Soil alone, MM = Minjingu Mazao
alone, C = Cattle manure compost, PM = Poultry manure compost, MM+CM = Minjingu
Mazao and cattle manure compost, MM+PM = Minjingu Mazao and poultry manure compost.
Each treatment was managed in nine different pots in Complete Randomized Design
(CRD) that is three orthogonal replications making total of 54 pots. All pots
were incubated at 60% moisture level for 7 days and then maintained at 30% moisture
level throughout the period of experiment. The minimum incubation period was
14 days for the first 3 pots of each treatment and the maximum was 42 days for
the last 3 pots of each treatment. Between the minimum and maximum incubation
periods, there were other 3 pots of each treatment analyzed for P at 28 days
from the onset of experiment.
Soil analysis was done before and during experimentation
periods. The soil was analyzed for pH, available P, total N, organic carbon and
corrected to organic matter
content before incorporating with treatments (Okalebo
et al., 2002
) and particle size distribution was determined by Bouyoucos
hydrometer method (Gee and Bauder, 1986
). In addition, at
the end of each incubation period, soil samples were taken from experimental pots
using a trenched 15 cm long knife. These soil samples were air-dried on magazines,
sieved in 2 mm sieve wire mesh and stored using paper bags. Thereafter, available
P for each sample was analyzed accordingly.
Statistical data handling: The data from incubated soil samples were
truncated and organized using MS-Excel computer programme including drawing
of columns and graphs. The data were analyzed based in one-way ANOVA design
in randomized blocks and the means compared based on Duncans Multiple
Range Test at 5% level. Furthermore, the Chi-square statistical test of Maximum
Likelihood was used to determine association effects of P-sources and days of
incubation to the quantities of P released. All statistics were performed using
GenStat Computer Software (Wim et al., 2007).
Properties of the study soil: The results of some physical and chemical
characteristics of the experimental soil are presented in Table
Quantities of P released from treatments at different periods of incubation:
The results of the quantities of P released from M-Mazao fertilizer, cattle
and poultry manures at different periods of incubation are presented in Table
Relationship between P-sources incubated and P released: The results
of the quantities of P released as affected by the association of P-sources
incubated are presented in Table 3 and 4
and Fig. 1.
|| Quantities of P released at different periods of incubation
|F stat: p>0.05 = NS, **p <0.01, ***p <0.001, the
means in the same column with different letter (s) differ statistically
Effects of M-Mazao fertilizer, cattle and poultry manures to quantities of
P released at different periods of incubation quantities of P released 14 days
Soil alone: The results of the soils
P obtained from soils incubated for 14 days with different treatments and their
combinations differed significantly (p<0.001) with the absolute control and
among the treatments (Table 2). Based on the in-situ soils
available P (7.9 mg kg-1) (Table 1), the P from
soils which were incubated with deionized water but without any treatment for
14 days increased to 8.4 mg kg-1 (Table 2), which
is 0.5 mg kg-1 (8.4-7.9 mg kg-1) increase in P due to
incubation. This was attributed to the time of incubation which probably allowed
P dissociation from soils P
retaining sites and/or Ca-chelating agents and from Mn, Fe and Al ox-hydroxides.
M-Mazao fertilizer: The P from soils which were treated with M-Mazao
fertilizer for 14 days (12.2 mg kg-1), which is 4.3 mg kg-1
(12.2-7.9 mg kg-1) increase in P (Table 2). This
was attributed to P contained in soil and in M-Mazao fertilizer. However, this
P was relatively higher by 3.8 mg kg-1 (4.3-0.5 mg kg-1)
than that obtained from soils incubated with deionized water alone.
|| Comparison of P from treatments at varying days of incubation
This shows that there was an adjustment of P released when M-Mazao fertilizer
is applied as a source of P in a Chromic Acrisol whose in-situ available P was
low (7.9 mg kg-1) (Table 1). These findings are
similar to the findings of Iqbal et al. (2010)
who report that the efficacy of inorganic fertilizers containing rock phosphate
improves soils physico-chemical parameters during composting.
Poultry manure: The P from soils which were incubated with poultry manure
for 14 days (15.9 mg kg-1) indicated 7.5 mg kg-1 (15.9-8.4
mg kg-1) soil P recovered, attributed to poultry manure over the
absolute control (Table 2). Similar findings are also reported
by Mujeeb et al. (2010) that poultry manure
proves better with 5.37% recovery of P in soil over the absolute control.
Cattle manure: Results showed that 17.9 mg of P per kg soil was obtained
from soils which were incubated for 14 days with cattle manure, which is 9.5
mg kg-1 more than the absolute control (8.4 mg kg-1) contributed
by cattle manure (Table 2). These findings suggest that even
though not all P is recovered from the soil but, other P was added to the soil
by cattle manure. The P recovered from soil because of incorporating cattle
manure could be attributed to the age of cattle and the type of feeds taken
by cattle. Similar findings are also reported by Scalenghe
et al. (2002) who indicate that long-term repeated applications of
fertilizers and livestock wastes have resulted in an increase in the soil P
M-Mazao fertilizer and cattle manure: The P (16.1 mg kg-1)
obtained from soils which were incubated for 14 days with cattle manure and
M-Mazao fertilizer in combination was 7.7 mg kg-1 (16.1-8.4 mg kg-1)
more than the absolute control (8.4 mg kg-1) (Table
2). These findings suggest that the P obtained was relatively lower than
that obtained in soils which were incubated with cattle manure alone (17.5 mg
kg-1) but larger than that obtained from soils which were incubated
with M-Mazao alone (12.2 mg kg-1). The findings indicate that cattle
manure posed differences in the quantities of P released from the soil. This
could be attributed to the organic materials from cattle manure which differ
in their contents of organic acids and in turn might have helped in dissolution
of P in soil apart from P from these organic materials. Similar findings are
reported by Mujeeb et al. (2010). In soils with
high P-fixing capacities, such as ferralsols, the organic acids released during
decomposition process may increase P availability by coating P adsorption sites
or via anion exchange reactions (Brady and Weil, 2008),
which could be the case for the P obtained in this soil.
M-Mazao fertilizer and poultry manure: The quantity of P obtained from
soils which were incubated with M-Mazao fertilizer and poultry manure in combination
(14.2 mg kg-1) was 5.8 and 2.0 mg kg-1 more than in the
absolute control (8.4 mg kg-1) and M-Mazao alone (12.2 mg kg-1),
respectively (Table 2). However, these P quantities were 1.7
mg kg-1 less than P obtained from soils which were incubated with
poultry manure alone (15.9 mg kg-1). These findings suggest that
poultry manure significantly adjusted the quantity of P released from soil and
from M-Mazao fertilizer.
Quantities of P released 28 days after incubation: The results of P
released from soils which were incubated with different treatments for 28 days
showed significant (p<0.01) decrease in the quantities of P among treatments
and with the absolute control (Table 2). In addition, the
P obtained from soils after 28 days of incubation were smaller than the quantities
obtained in soils after 14 days of incubation. The general observation showed
that decrease in quantities of P released could be attributed to increased P
fixation by soils exchange sites as time of contact increased. Kisetu
and Mrema (2010) report that P retained or fixed by soils increased with
time of contact and varied with moisture content of the equilibrating medium.
The data taken 28 days after incubation showed that the quantities of P (mg
kg-1) were in the order: Poultry manure (14)>M-Mazao+cattle manure
(7.1)>cattle manure (5.1)>M-Mazao+poultry manure (4.5)>M-Mazao (4.0)>soil
alone (1.9) (Table 2).
These results indicate that P decreased rapidly for absolute control and other
treatments except P from soils which were incubated with poultry manure, which
decreased only very slightly (1 mg kg-1) (Fig. 1).
These findings suggest that poultry manure is capable of releasing substantial
quantities of P through its decomposition and by dissociating P contained in
soils fixing sites. In addition, the findings suggest that P fixation
in soil was decreased due to protective action of poultry manures. Mujeeb
et al. (2010) report that the concentration of solution P in soil
increased with increased organic matter contents. Several mechanisms have been
proposed to explain decrease in P adsorption capacity (Iyamuremye
and Dick, 1996) including: (1) Competition with phosphate anions for adsorption
sites by organic anions produced from decomposition of plant materials and (2)
Saturation of adsorption sites by P added to the soil.
Quantities of P released 42 days after incubation: The quantities of
P released from soils which were incubated with different treatments for 42
days decreased significantly (p<0.001) among treatments and with the absolute
control. In addition, P obtained from soils after 42 days of incubation were
smaller than P obtained after 14 days of incubation but far smaller than those
obtained after 28 days of incubation (Table 2), indicating
increase in P fixed with increase in time of contact with the soil.
|| Chi-square test for association between P-sources incubated
and P released
|Probability level (under null hypothesis) p = 0.465, Likelihood
Chi-square value is 9.72 with 10 df, F stat: *p ≤0.05; **p<0.01 (picked
from Table 4)
The results of the data taken 42 days after incubation showed that the quantity
of P in soils treated with poultry manure was relatively larger (5.1 mg kg-1)
than P from other soils (Table 2). On the other hand, the
quantities of P (mg kg-1) obtained from other soils were in the order:
M-Mazao+poultry manure (2.8)>soil alone (1.3)>M-Mazao (0.8)>cattle
manure = M-Mazao+cattle manure (0.6) (Table 2). These findings
suggest that soils incubated with M-Mazao fertilizer and incorporation of organic
manures for a long period (42 days) proves no agronomic importance in enhancing
P availability to P depleted soils. The inference to be drawn from this is that
there is a need to incorporate composted organic manures well in advance in
the season before the onset of rains and in soils which are not flooded.
Relationship between P-sources incubated and P released: The chi-square
test (Table 3 and 4) assessed independence
of two classifications, P-sources (treatments) and incubation period. Essentially,
it tested whether the distribution of P released between the two categories
of one factor appears to change according to the categories of the other factor.
The test statistic (p = 0.465) obtained from this study indicates that the two
classifying factors, P-sources and P released, are independent; that is, there
is no evidence that they are associated in effecting release of P from soils.
The goodness of fit for the chosen distribution is indicated by the residual
deviances (Table 3), which have an asymptotic chi-square distribution.
The deviance is also the preferred statistic for comparison of nested models.
|| Comparison of P released in different days of incubating
|| Statistical contributions to the Chi-square of association
existing between the studied P-sources and quantities of P released
|Key: The numerals 1, 2, 3, 4, 5 and 6 correspond to soil alone
(S), M-Mazao (MM), Poultry Manure (PM), Cattle Manure (CM), MM+CM and MM+PM,
The quantities of P released from the study soils varied significantly with
P-sources and decreased with increased period of incubation (Table
3). It was observed from the data that P release decreased slowly with increasing
period of incubation from 14 to 42 days. The highest P released from all treatments
was noted for data taken 14 days after incubation and the lowest was noted for
data taken 42 days after incubation (Table 3; Fig.
1). However, soil alone and soils treated with M-Mazao being it alone or
in combination with organic manures showed a resistant decrease in P, which
attained almost its threshold of not below 0.5 mg kg-1 (Fig.
2). This low decrease in P released by soils could be attributed to increase
in P fixed by soil particles as time of contact with soil increased. These results
corroborate the findings of Jalali and Zinli (2011)
who report that kinetics of P release from soils can be described as an initial
rapid rate followed by a slower rate. The same pattern of P release is also
observed by Do Carmo Horta and Torrent (2007) and Nafiu
The greater quantity of P released by soil incubated with poultry manure for
14 and 28 days than P from other soils might be due to distortion of clay particles
and more native P in the poultry manure or the adsorbed P might be loosely held
by soil particles that were easily released. However, the discrepancy observed
for P released between 28 and 42 days of incubation could be attributed to high
levels of uric acid produced by poultry manure which suspended P in solution
hence low quantity desorbed/released from soil particles. These findings are
in agreement with those of Kaloi et al. (2011)
who report that less release of P with increased time of incubation is due to
more positively P Carried over (PCO) soil solution which cannot easily be captured
by normal extraction.
On the other hand, in case of soil alone and soils treated with M-Mazao being
it alone or in combinations, P in some of them was probably tightly held by
soil particles and tends to release slowly due to more sorbing energy. These
results are in agreement with those of Do Carmo Horta and
Trorrent (2007) who report that the ratio of fast desorbable P or total
desorbable P to sorbed P increased with increasing degree of P saturation in
Incubating the soils low in P with different P-containing soil amendments such
as cattle and poultry manures and M-Mazao fertilizer substantially increased
P levels in soils as the period of incubation exceeded 14 days through 28 and
42 days. However, poultry and cattle manures gave relatively promising quantities
of P compared with M-Mazao fertilizer between 14 and 28 days of incubation.
Authors are thankful to Professor Balthazar Michael Msanya of the Department
of Soil Sciences at the Sokoine University of Agriculture, Morogoro Tanzania
for resourceful guidance and material he provided including calibrated sampling
knife used during sampling of incubated soils in pots for research.
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