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Phosphorus Uptake and Use Efficiency by Cowpea in Phosphocompost and Chemical Fertilizer Treated Nutrient Degraded Acid Soils
Oyeyiola YB1 and Omueti JAI2*
1Department of Crop Production and Soil Science, Ladoke Akintola University of Technology Ogbomoso, Nigeria
2Department of Agronomy, University of Ibadan, Nigeria
Submission: June 14, 2016; Published: July 08, 2016
*Corresponding author: Omueti JAI, Department of Agronomy, University of Ibadan, Nigeria, Tel:+2347031128303; Email:firstname.lastname@example.org
How to cite this article: Oyeyiola YB, Omueti JAI. Phosphorus Uptake and Use Efficiency by Cowpea in Phosphocompost and Chemical Fertilizer Treated Nutrient Degraded Acid Soils. Agri Res & Tech: Open Access J. 2016; 1(5): 555578. DOI: 10.19080/ARTOAJ.2016.02.555578
Phosphorus uptake on chemical fertilizer treated tropical soils is challenged by high phosphorus fixing and leaching potentials. Phosphocompost is a new organic fertilizer in Nigeria. Phosphorus uptake and use efficiency of phosphocompost was studied on two acid soils from Ilesha and Ogbomoso, Nigeria during 2012 and 2013 cropping seasons. Two phosphocompost: C1 and C2 applied at 2.5 and 5.0 t/ha were investigated. NPK 15:15:15 at 40 kg P2O5/ha, SSP (40 kg P2O5/ha) - urea mix (20 kg N/ha), sole SSP (40 kg P2O5/ha), sole lime (1 t/ha) and an unamended plot were compared. Cowpea was the test crop. Data were taken on soil available P, phosphorus uptake, phosphorus use efficiency (PUE), and relative agronomic efficiency using data on soil available P (RAEp) and cowpea dry shoot weight (RAEdsw). Phosphorus uptake was significantly (p<0.05) higher in phosphocompost compared to chemical fertilizer treated and untreated plots. Phosphorus uptake ranged from 1.3 – 7.9, 1.0 – 4.4 and 0.5 – 1.7 kg/ha in phosphocompost, chemical fertilizer and unamended plots respectively across the two cropping seasons. The PUE were higher in chemical fertilizer treated plots with a range of 11.4 -152.9 % while phosphocompost gave a range of 2.2-19.8 % across the two locations. Regression analysis revealed RAEp, RAEDSW, available P and P uptake to contribute up to 82, 83, 82 and 75 % respectively to cowpea grain yield in Ogbomoso experimental location. Increasing RAEp, available P, P uptake, PUE and soil pH were dominant predictors for increased cowpea grain yield in Ilesha experimental location.
Phosphorus is an essential macronutrient that plays vital role in living organisms. Adequate P availability results in improved root growth, crop quality, energy storage and higher grain yield in crops . It is highly limiting in most tropical soils [2,3]. The low activity clay dominating mineral constituent of the highly weathered tropical soils has been identified as a factor limiting availability of P in soils . Acid tropical soils are characterized by high concentrations of oxides and hydroxides of Al and Fe that have insatiable appetite for P . Management practices including the use of chemical P fertilizers and liming materials are popular in optimizing crop performance and yield on nutrient degraded soils in the tropics . The limitations to use of P fertilizer are rising procurement cost, susceptibility losses to leaching, run off (on sandy textured soils) and fixation by soil inorganic colloids .
Nutrient use efficiency by crops is the ability of crops to produce high yield in soils limited in the nutrient added . Nutrient use efficiency is high when enhanced crop yield is obtained from reduced fertilizer input cost and nutrient losses into the soil environment. Phosphorus use efficiency on field treated with conventional chemical fertilizers have been reported low (range of 5 – 40 %) for many tropical soils . Low P use efficiencies in chemical fertilizers are contributed mainly by losses to leaching, run-off and fixation by soils . Nutrient losses from farms are important in soil degradation and underground water pollution . Benefits of improved soil organic matter on soil physical and chemical properties as it affects nutrient use efficiency have been reported . Soil organic matter from applied green manure, crop residues, animal manure and compost improved soil aggregate stability, increased water and basic cation holding capacities and chelate toxic Al and Fe .
Phosphocompost is phosphorus enriched compost . It is
a relatively new soil amendment in many developing countries in
the tropics. It is however popular in areas with natural depot of
rock phosphate. It is prepared from mixture of rock phosphate,
carbon sources (e.g. sawdust, rice bran, plant residues etc)
and protein sources (e.g. animal manure) are common [12,13].
Phosphocompost when compared with conventional compost has
lower ammonium-N and C/N ratio with improved total nitrogen,
soluble phosphorus and organic acids (formic, citric, Lactic and
acetic acids) . The application of phosphocompost on strongly
acid soils had been reported to improve soil pH, organic matter,
total nitrogen, available P, P uptake of crops [14,15] compared
to chemical fertilizers . The researchers  also reported
the ability of phosphocompost to chelate toxic Al ions helps to
increase phosphorus use efficiency. Cowpea is an important grain
legume in Africa. It serves as major source of dietary protein for
man. Phosphorus deficiency and soil acidity are important factors
militating against high yield of cowpea on tropical soils .
Importance of phosphorus in cowpea nutrition has been reported
by  to initiate nodule formation and enhance efficiency of
symbiotic nitrogen fixing organisms (rhizobium). The objectives of this study were to assess the P availability, uptake and use
efficiencies of phosphocompost (by cowpea) prepared from bone
meal fortified rice bran and sawdust based composts.
The study was conducted at two sites in Oyo and Osun States,
south western Nigeria (Figure 1). The locations and history of
the experimental sites are given in (Table 1). Osun study location
was at the Teaching and Research Farm of the Leventis School of
Agriculture, Imo, and Ilesha while that of Oyo was at the Teaching
and Research Farm of Ladoke Akintola University of Technology,
Ogbomoso. The soils of the Ilesha study site originate from
rocks rich in amphibole, gneiss and biotite schist. The soil is
characterized by reddish colour and low base saturation . It
is classified as Ultisols using Soil Survey Staff (2010) according to
. Soil at the Ogbomoso study site was formed on a basement
complex and characterized by large concretions resulting in hard
pan formation . The soil is sandy and greyish with high base
saturation . The soil is classified as Alfisols using Soil Survey
Staff (2010) according to .
The fields were sampled to depth of (0-20) cm. The soil
samples collected were air dried, passed through 2 mm sieve
and subjected to routine analysis. The physical and chemical
analyses of the soil samples were carried out at the Department of
Agronomy, University of Ibadan. Particle size was determined by
hydrometer method . Soil pH was determined on a 1:2 (soil:
water) ratio after 15 minutes equilibration period using a glass
electrode calibrated in pH buffers 4, 7 and 9. Organic carbon was
determined by the dichromate wet oxidation method as described
by . Phosphorus was extracted with Bray P-1 solution and the
P in the extract was determined by Molybdate blue colour method
of  with Spectronic 20. Exchangeable cations (Ca, Mg, K and
Na) were extracted with 1 N NH4OAc (pH 7) at a soil: extracting solution ratio of 1:10 for 15 minutes. The concentration of Ca
and Mg were read on the Atomic Absorption Spectrophotometer
while those of K and Na were read on the Flame Photometer.
Exchangeable acidity was extracted with 1 N KCl and titrated
against 0.01N NaOH. Exchangeable Al was determined by further
titration of the same extract with 0.01N HCl as described by .
The effective cation exchange capacity (ECEC) was obtained by the
sum of the total exchangeable bases (TEB) and total exchangeable
acidity (TEA). Total Nitrogen was determined by Macro-Kjeldahl
method as described by Bremner .
The fields were mechanically cleared, ploughed and harrowed.
It was laid out in eleven plots per replicate with each measuring
2 m x 2 m. Two phosphocompost (preparation process described
in ) tagged C1 and C2 applied at 2.5 and 5 t/ha (equivalent to
1 and 2 kg/4 m2) were investigated. The bone meal for compost
fortification was applied at the rate of 40 kg P2O5/ha equivalent
to 546 g/ 4 m2. Three chemical fertilizer plots viz: Urea applied at
20 kg N/ha (equivalent to 17.7 g/4 m2) mixed with Single Supper
Phosphate (SSP) applied at 40 kg P2O5/ha (equivalent to 88.9 g/4
m2), NPK 15:15:15 applied at 40 kg P2O5/ha (equivalent to 106
g/4 m2) and a plot that received SSP at 40 kg P2O5/ha (equivalent
to 88.9 g/4 m2) were included. Plots that received lime alone and
no amendment were also compared. The experiment was laid out
in a randomized complete block design with three replications
resulting in 33 experimental plots per location. Phosphocompost
treatments were applied only during the 2012 cropping season.
The 2013 cropping was used to assess residual potentials of the
phosphocompost on soil P availability, uptake and use efficiency
by cowpea. Similar chemical fertilizer rates as 2012 cropping were
however reapplied to chemical fertilizer plots during the 2013
cropping. Cowpea (Ifebimpe variety) was the test crop during
both cropping seasons.
Soil samples collected at harvesting were analysed for available
P using the procedure earlier described. Cowpea grain yield
and dry shoot weight were assessed at harvesting. Phosphorus
contents in the shoots were determined after harvesting. The
Vanado-molybdate yellow method was followed for phosphorus
determination as described by . The phosphorus content in
the shoot was used for the estimation of phosphorus uptake as:
P uptake = Phosphorus content x Dry shoot weight .
Phosphorus use efficiency (PUE) and relative agronomic efficiency
(RAE) of the phosphocompost using dry shoot weight (RAEDSW)
and soil available P data (RAEP) were estimated following the
formulae adopted by .
PUE = P uptake from treatment – P uptake from control x 100
RAEDSW =Dry shoot weight from PC - Dry shoot weight from
control x 100
Dry shoot weight from SSP - Dry shoot weight from control
This formula was modified (using soil available phosphorus
RAEP = Avail. P from Phosphocompost–Avail. P from control
The soil, plant and yield data collected from each field were
subjected to analysis of variance using Genstat statistical package
and significant means were separated using Duncan’s multiple
range test at 5 % probability level. Regression analysis was utilized
to predict contributions of the phosphocompost efficiency data to
cowpea grain yield.
The physical and chemical characteristics of the soils are
shown in (Table 2). The soil at Ogbomoso experimental location
(OEL) was moderately acidic with pH 5.7 while that at Ilesha (IEL)
was strongly acidic with pH 4.8. The two soils were deficient in
available P, total N, organic carbon and exchangeable calcium.
Exchangeable acidity concentration was high in IEL soil series and
low in OEL.
The nutrient contents of the phosphocompost tested are
shown in (Table 3). Phosphocompost C1 was higher in phosphorus content while C2 was higher in nitrogen and organic carbon. Both
however were alkaline in reaction making them suitable for use
on acid soils.
Phosphocompost application significantly increased available
phosphorus in the soils compared to lime, chemical fertilizers
and AC (Table 4). Phosphorus availability increased with
increasing phosphocompost application rate. Similar available
P concentrations were observed from all the chemical fertilizer
treated plots during each cropping per location. Higher soil
available P concentrations were recorded from IEL compared to
Phosphocompost and chemical fertilizers improved
phosphorus uptake in both soils compared to lime and AC (Table
5). Phosphocompost gave P uptake range of 1.9- 5.6 and1.3- 7.9
kg/ha in IEL and OEL respectively across the two cropping. A
range of 1.0 - 4.4 and 1.0 – 3.1 kg/ha were observed from chemical
fertilizer treated soil from IEL and OEL respectively across the two cropping. Phosphocompost C1 increased P uptake with reducing
application rate in IEL while it increased P uptake with increasing
application rate in OEL. Phosphorus uptake however reduced
generally across all the phosphocompost treated plots in the 2013
a. Phosphorus use efficiencies of phosphocompost and chemical
fertilizers by cowpea: Phosphorus use efficiencies of treatments
applied were highest in chemical fertilizer treated plots at both
experimental locations (Table 6). The NPK fertilizer consistently
gave highest PUE at IEL. Lower phosphocompost application
rate had higher PUE at both locations except in phosphocompost
C1 at OEL during 2012 cropping. Phosphocompost C1 gave PUE
range of 6.6-17 and 9.7-17.6 % in IEL and OEL respectively.
Phosphocompost C2 gave a range of 7.8- 17.4 and 2.2 – 21.3 % in
IEL and OEL respectively.
a. Relative agronomic efficiencies of phosphocompost, lime
and chemical fertilizers using soils available P (RAEP) cowpea dry
shoot weight (RAEDSW) data in two acid soils: Relative agronomic
efficiencies using the soil available phosphorus data (RAEP) were
highest in the phosphocompost treated plots at both experimental
locations compared to chemicals fertilizer and lime treatments
(Table 7). The RAEP were higher across all the treatments during
2012 cropping season at both locations. The efficiency of available
P released from the applied phosphocompost C1 was 2 and 4 times
higher than the referenced single super phosphate fertilizer in IER
and OEL respectively at the end of 2013 cropping season. The
RAEDSW on the other hand was higher across all the treatments at
both locations during the 2013 cropping season. Phosphocompost
application again had higher RAEDSW compared to chemical
fertilizer and lime except in IEL during 2012 cropping season.
Higher application rate of phosphocompost C1 and lower rate of
C2 gave higher RAEDSW at both locations.
a. Contributions of selected soil chemical and phosphocompost
efficiency parameters to cowpea grain yield in two acid soils: The
contributions of selected soil chemical and phosphocompost
efficiency parameters to cowpea grain yield at the end of the trial
are presented in (Figures 2 & 3). All the parameters considered
had positive relationship with cowpea grain yield. However, at the
OEL, RAEp, RAEDSW, available P and P uptake contributed up to
82, 83, 82 and 75 % in the cowpea grain yield. Increasing RAEp,available P, P uptake, PUE and soil pH were dominant predictors of
increased cowpea grain yield in IEL.
Phosphocompost applications increased available P in the
soils studied. This is first attributed to increases in soil pH (data
not presented) brought about by the phosphocompost applied.
Increases in soil pH had been reported on acid soils treated
with organic materials [15,26,27]. Increasing soil pH enhanced
P release from adsorbed site of the soil colloid into soil solution and eventual uptake by cowpea. The increased P uptake in
phosphocompost treated soils was most likely due to plant
establishment and proper root development induced by the water
soluble P mineralized into the soil by the phosphocompost. This
is in agreement with the findings of [13,28].  Identified toxic
levels of Al and Ca deficiencies in acid soils as dominant factors
restricting root elongation in plants sown on acid soils which
impair efficient nutrient uptake. This is possibly the situations
in the unamended and chemical fertilizer treated plots in this
work. Ability of phosphocompost to improve nutrient uptake, use
efficiency and over all grain yield had been reported .
Phosphorus use efficiencies (PUE) were generally lower
in phosphocompost compared to chemical fertilizer treated
plots. It was exceptionally low in 5C1 in IEL and 5C2 in OEL
. Also observed higher PUE in single super phosphate
over phosphocompost in their work. This suggests an inverse
relationship between available P in phosphocompost treated
soils and PUE. Treatments 5C1 and 5C2 were responsible for
highest available P in their respective treated soils. Interestingly,
NPK treated soils during similar cropping gave least available P
in both soils. These lower PUE in phosphocompost compared to
chemical fertilizer may suggest possible losses/uses of phosphate
ions by phosphocompost through other means than plant uptake.
One of the possible ways is utilization by increasing microbial
population in the treated soils. Phosphorus is a major source of
energy to living things including soil microbes. The reducing PUE
with increasing application rate rightly affirms these findings.
Microbial population and activities were reported to increase in
soils with increasing application rate of organic amendments .
The result therefore was increased P usage from the soil P pool
for metabolic activities and body building by the microbes .
Had earlier explained the fate of biologically fixed phosphate. He
described it as a better form of P fixation compared to inorganic
P fixation by oxides of Al and Fe. Phosphorus fixed biologically by
soil microbes will eventually be released into readily available P
form when the microbes expire.
The relative agronomic efficiencies (RAE) were very high in
phosphocompost compared to chemical fertilizer and sole lime
treated soils . Also reported higher RAE in phosphocompost
compared to single super phosphate and rock phosphate. The
results from the present work suggests phosphocompost to be a
more efficient P source in the soils studied compared to chemical
fertilizers tested. The phosphocompost prepared from agro waste
(sawdust, rice bran, poultry manure and bone meal) did not only
reduce environmental pollution associated with the reckless
discharge of these wastes into the environment but gave an
environmentally friendly fertilizer. Similar higher RAE in organic
amendment integrated with diammonium phosphate (DAP)
treated soils had been reported  compared to sole DAP and
poultry manure . Attributed the ability of phosphocompost
to easily supplement readily available phosphate ions in the soil
solution to the generally higher relative agronomic efficiencies
recorded in soils been treated by phosphocompost.
Usage of phosphocompost at both rates studied on acidic
nutrient degraded soils in Ilesha and Ogbomoso, south western
Nigeria will go a long way to reduce high application rates of
chemical fertilizers on these fragile soils. Phosphocompost will
not only reduce P deficiencies, improve P uptake and grain yield
of crops but also enhance recycling of agro-waste into useful soil
amendments (which is not a usual practice among farmers in
the experimental locations). It will also reduce environmental
pollution associated with reckless disposal of raw agro-wastes.