Effect of Phosphorus fertilizer on growth and yield of cowpea (Vigna unguiculata)

Abstract

Phosphorus is important for cowpea production in many tropical African soils with inherent low phosphorus fertility. Most farmers in Africa, however, do not have access to phosphorus fertilizer. Selection of cowpea lines that produce good yield under low soil phosphorus or those with high phosphorus use efficiency can be a low input approach to solving this problem. This research work was conducted in pot trials at the teaching and research farm of Michael Okpara University of Agriculture, Umudike, in the south eastern part of Nigeria to determine the effect of different phosphorus levels on growth and yield of three varieties of cowpea (Vigna unguiculata (L.) Walp), obtained from the germplasm unit of International Institute of Tropical Agriculture, Ibadan. The experiment consists of five phosphorus levels (0kgha-1, 20kgha-1, 40kgha-1, 60kgha-1 and 80kgha-1) each of which contains seven replicates. Phosphorus fertilizer significantly enhanced growth and yield characters of the cowpea varieties used; plant height, leaf area, number of leaves and number of branches in all the weeks of measurement were significantly improved. Phosphorus also had a significant effect (p>0.05) on seed yield per treatment, weight of 50 seeds, number of nodules, weight of nodules and total aboveground dry matter in all varieties used. However, variations were observed in the responses of the different cowpea varieties to phosphorus application. High yield values were observed in variety three; IT99K-573-2-1, followed by variety two; IT99K-573-1-1 and variety one; IT97K-499-35. Highest value in all the yield characters measured was observed in variety three: IT99K-573-2-1 at phosphorus fertilizer rate of 40kgha-1. When phosphorus is available, IT99K-573-2-1and 40kgha-1 phosphorus application rate is recommended.

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Nigerian Journal of Agriculture, Food and Environment. 7(3):51-54
Published September, 2011
Osaigbovo and Orhue, 2011
NJAFE VOL. 7 No.3, 2011 51
EFFECT OF PALM OIL MILL EFFLUENT ON SOME SOIL
CHEMICAL PROPERTIES AND GROWTH OF MAIZE (Zea mays L)
Osaigbovo
1
, A. U. and Orhue
2
, E. R.
ABSTRACT
1
Department of Crop Science, Faculty of Agriculture, University of Benin, Benin City, Nigeria.
2
Department of Soil Science, Faculty of Agriculture, University of Benin, Benin City, Nigeria.
A greenhouse study was conducted at the Faculty of Agriculture, University of Benin, Benin City, Nigeria to evaluate the effect
of palm oil mill effluent on some soil chemical properties and growth of maize (Zea mays L.). Five rates of the effluent namely
0, 50, 100, 150 and 200 ml per 2 kg soil were used in a completely randomized design with three replicates. Results revealed
that the soil Nitrogen, Phosphorus, potassium, Magnesium, Calcium, organic carbon, exchangeable acidity, Effective Cation
Exchange Capacity and sodium increased with increasing effluent applications while soil pH was in acidic condition. The
plant height, leaf area, number of leaves stem girth and nutrients uptake by the plant significantly (P < 0.05) decreased with
increasing palm oil mill effluent treatments.
Key words: Palm oil mill effluent, rate, soil properties, maize, uptake, chemical,
INTRODUCTION
Oil palm (Elaeis guineensis Jacq.) is of domestic and industrial importance because of the oils obtained from it.
The palm oil is obtained from the mesocarp of the fruit while the palm kernel oil is obtained from the kernel. The
sequence of processing of palm oil from oil palm include; reception of bunches, sterilization, threshing,
digestion/crushing, settling, purification, clarification, packaging, storage and distribution. The waste generated
during these processes is known as the palm oil mill effluent. The waste is let out into the environment of which
soil is one of the major recipients. Thrillaimuithus (1978) observed that for every ton of palm oil processed, two
or three tons of palm oil mill effluents are generated. Thus, this may pose a disposal problem in a large-scale
production.
Studies on the use of palm oil mill effluent as soil amendments have gained attention in recent times. The
controlled application of the effluent has been reported to increase soil pH, K, Ca, Mg and organic matter (Poon,
1982; Lim and P’ng 1983; Lim et al., 1983; Onyia et al., 2001; Akwute and Isu, 2007), soil water holding
capacity and porosity (Logan et al., 1997) The application of palm oil mill effluent has been reported to increase
the growth, dry matter, grain yield and nutrient content of maize (Nwoko and Ogunremi, 2010) and the growth of
tomato plant (Nwoko et al., 2010). A lot of palm mill effluent is generated in Edo state with little or no
utilization agriculturally to ascertain its potentials. The objective of this study was to assess the effect of palm oil
mill effluent on some soil chemical properties and early growth of maize (Zea mays L.).
MATERIAL AND METHODS
The preliminary investigation was sited in the greenhouse at the Faculty of Agriculture, University of Benin,
Benin City, Nigeria. Benin City the capital of Edo State lies within latitude 6.5
o
N and longitude 5.8
o
E and is in
area described generally as Benin lowland. The climate of Benin is tropical with two major seasons namely the
rain (April-October) and dry (November-March) seasons. Rainfall is bimodal, peaking usually in July and
September, with a brief drop in August. Minimal rainfall occurs in January and February, followed by the onset of
heavy rainfall in April. The mean annual rainfall is 2300 mm while the entire average temperature is 32
o
C. The
mean relative humidity in the area is about 70%. Benin City is both commercial and agrarian City producing
varieties of arable crops including maize.
The palm oil mill effluent was obtained from Nigerian Institute for Oil Palm Research (NIFOR) in Edo State,
while the maize seeds were obtained from the Plant Breeding Unit of the Department of Crop Science, University
of Benin, Benin City, Nigeria. The soil used was collected from top 15 cm of an uncultivated field left fallow for
three years after several years of continuous cropping with maize plant. The soil was bulked, mixed thoroughly
and air-dried and then sieved to remove debris. Thereafter, 2 kg of the composite soil was weighed and put into
each of the polythene bag. The palm oil mill effluent was applied at the rates of 0, 50, 100, 150; 200 ml per 2 kg
soil were used in a completely randomized design and replicated three times. The effluent applied was thoroughly
mixed with the soil, watered and left for 4 weeks to allow for adequate mineralization and equilibration before
planting.

Nigerian Journal of Agriculture, Food and Environment. 7(3):51-54
Published September, 2011
Osaigbovo and Orhue, 2011
NJAFE VOL. 7 No.3, 2011 52
Four seeds were sown per polythene bag and thinned to one, two weeks after germination. Growth parameters
were measured at 2 weeks interval, starting from the second week after planting. At 8 weeks after planting, the
plants were harvested; the shoots were dried in the oven at 72
o
C for 72 hours to a constant weight used in
computing the nutrient uptake
Soil and palm oil mill effluent analysis
The soil and the palm oil mill effluent as well as the plant analyses were carried out before and after the
experiment, respectively. The soil pH was determined in a 1:1 soil to water ratio using glass electrode pH meter
while the palm oil mill effluent pH was read directly. The total solids was determined by methods of Ademoroti
(1996). The soil particle size was determined using the hydrometer method of Day (1965). The organic carbon
content of both soil and the effluent was determined by using the chromic acid wet oxidation procedure as
described by Jackson (1962). The total nitrogen, available phosphorus, exchangeable bases as well as
exchangeable acidity were determined using methods of Udo et al. (2009). The effective cation exchange capacity
was calculated as the sum of exchangeable bases and exchangeable acidity.
Plant analysis
The ground 50 g plant materials were digested with a mixture of 5 ml HNO
3
and 2 ml HCIO
4
acids. Thereafter, 15
ml of water was added and the digest solution filtered through an acid-washed filter paper into 50 ml volumetric
flask. The filter paper was washed with water and the filtrate dilutes to volume with deionized water. The
sodium, potassium, Calcium, Magnesium contents were determined by the use of atomic absorption
spectrophotometer. Phosphorus content was determined by perchloric acid digestion method (AOAC, 1970).
Nitrogen was determined by the micro-kjeldhal method of Jackson (1962). The data obtained were analysed by
Genstat statistical version. Duncan Multiple Range Test was used in separating the means at 5% level of
probability.
RESULTS AND DISCUSSION
Properties of palm oil mill effluent
The physico-chemical properties of the palm oil mill effluent (Table 1) showed that it contains nutrient elements
such as N, P, K, Mg, Ca and Na. The effluent is acidic and higher in total solids.
Pre-trial soil properties
The pre-trial soil properties are shown in Table 2. The soil used was acidic and have low percentage base
saturation. The nutrient components of the soil were also low. The N, P, K, Mg and Ca were below the critical
values of 1.5-2.0 gkg
-1
, (Sobulo and Osiname, 1981), 10-16 mgkg
-1
(Adeoye and Agboola, 1985), 0.16-0.25
cmolkg
-1
, (Akinrinde and Obigbesan, 2000), 0.2-0.4 cmolkg
-1
(Adeoye and Agboola, 1985) and 2.50 cmolkg
-1
(Akinrinde and Obigbesan, 2000) respectively.
Post-trial soil properties
The soil organic carbon, N, P, K, Mg, Ca, Na, exchangeable acidity and ECEC significantly (P < 0.05) increased
with increasing levels of palm oil mill effluent. The increase in the soil nutrient components may be attributed to
the palm oil mill effluent applied. This result further strenghten earlier findings of Nwoko et al. (2010) and
Akwute and Isu (2007). The soil pH however remained in acidic conditions at all levels of palm oil mill effluent
treatments probably due to acidic nature of applied effluent.
Effect of palm oil mill effluent on the growth of maize (Zea mays L)
The influence of palm oil mill effluent on number of leaves, height, leaf area and stem girth are shown in Tables
3, 4, 5, and 6 respectively. The results showed that the maize grown in the control treatment was significantly (P <
0.05) higher than palm oil mill effluent treated plants in all the growth parameters measured. The oily nature of
the effluent may have created anaerobic condition in the soil which led to reduced uptake of nutrients needed for
maize growth. Similar result was earlier reported by Kitikum et al. (2000).
Effect of palm oil mill effluent on maize nutrient uptake
The nutrient uptake as influenced by palm oil mill effluent is depicted in Table 7. The nutrient uptake declined
significantly (P < 0.05) with increasing effluent application. The decrease in nutrient uptake may be due to oily
nature of the effluent. Furthermore, the reduced nutrient uptake in the presence the effluent could be due to strong
adsorption in the soil as earlier reported by Drewes and Blume,(1977).
CONCLUSION
In the trial, the soil nutrient content of the treated soil increased while the nutrient uptake and the plant growth
were reduced with increasing effluent application. Though, palm oil mill effluent contains nutrients that are
necessary for the growth of maize, positive effects of these nutrients were not reflected as indicated by the growth
and nutrients uptake by maize plant.

Nigerian Journal of Agriculture, Food and Environment. 7(3):51-54
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Osaigbovo and Orhue, 2011
NJAFE VOL. 7 No.3, 2011 53
REFERENCES
Ademoroti, C. A. (1996). Standard methods for water and effluent analysis. Published by Foludex Press, Ibadan,
Nigeria. 182pp
Adeoye, G. O. and Agboola, A. A. (1985). Critical levels of soil pH, available P, K, Zn and Mn and maize ear
leaf content of P, Cu and Mn in sedimentary soil of Southwest Nigeria. Fertilizer Research 6: 65- 71
Akinrinde, E. A. and Obigbesan, G. O. (2000). Evaluation of fertility status of selected soil for crop production in
five ecological zones of Western Nigeria. Proceeding of the 26
th
Annual Conference of Soil Science
Society of Nigeria. University of Ibadan. October 30 - November 3 279-288
AOAC (1970). Official methods of analysis, Association of Official Analytical Chemists (AOAC) Ed
11Washington D. C
Day, P. R. (1965). Particle fractionation and particle size analysis Agronomy 9: 545-567
Drewes, H. and Blume, H. P. (1997). Effect of movement and sorption of herbicide in agricultural soils. Forsh
Sonderh 33: 104-113
Jackson, M. L. (1962). Soil chemical analysis New York: Prentice Hall.
Lim. K. H., Wood, B. J. and Lal, A. L. (1983). Effect of palm oil mill effluent (POME) on oil palm through
flatbed system. Proceeding of the seminar on land application of oil palm and rubber factory effluent
Serdang, October 1983 401p
Lim, K. H. and P
,
ng T. C. (1983). Land application of digested palm oil mill effluent by sprinkler system.
Proceeding of the seminar on land application of oil palm and rubber factory effluent. Serdang, October,
1983. 401p
Logan, I., Linsday, B. J., Goins, I. E and Ryan, J.A. (1997). Field assessment of sludge metal bioavailability to
crops: Sludge rate response Journal of Environmental Quality 26: 534-550
Nwoko, C. O. and Ogunremi. S (2010). Evaluation of palm oil mill effluent on maize (Zea mays L) crop: yield,
tissue nutrient content and residual soil chemical properties Australian Journal of Crop Science 4(1) 16-
22
Nwoko, C. O., Ogunremi. S., Nkwocha, E. E. and Nnorom, I. C. (2010). Evaluation of phytotoxicity effect of
palm oil mill effluent and cassava mill effluent on tomato (Lycopersicum esculentum) after pretreatment
option. International Journal of Environmental Science and Development 1: 67-72
Okwute, L. O. and Isu, N. R. (2007). The environmental impact of palm oil mill effluent(pome) on some physic-
chemical parameters and total aerobic bio-load of soil at a dumpsite in Anyigba, Kogi State Nigeria.
African Journal of Agricultural Research 2(12): 658-662
Onyia, C. O., Uyub, A. M., Akuma, J. C. L., Norulaimi, N. A and Omat, A. K. M. (2001). Increasing the fertilizer
value of palm oil mill sludge: Bioaugmentation in nitrification. Water Science and Technology 44(10):
157-162
Poon, Y.C. (1982). Recycling of palm oil mill effluent in the field. Proceeding of Rubber Research Institute of
Malaysia, Kualar Lumpar, October, 1982. 386p
Sobulo, R.A. and Osiname, O. A. (1981). Soils and fertilizer use in Western Nigeria. Research Bulletin. No 11.
I.A.R.T University of Ife.
Thillaimuthus, S. (1978). The environment and the palm oil industry: a new solution, incineration of sludge.
Planter 54: 228-236.
Udo, E. J., Ibia, T. O., Ogunwale, J. A., Anuo, A. O. and Esu, I. E. (2009). Manual of soil, plant and water
analysis. Sibon books Ltd, Lagos, Nigeria.
Table 1: Properties of palm oil mill effluent
Characteristics Value
pH 4.8
Organic C % 23
TOTAL N mg/l 1400
Available P mg/l 400
Potassium mg/l 1800
Magnesium mg/l 700
Calcium mg/l 439
Sodium mg/l 120
Total solids mg/l 2899

Nigerian Journal of Agriculture, Food and Environment. 7(3):51-54
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Osaigbovo and Orhue, 2011
NJAFE VOL. 7 No.3, 2011 54
Table 2: Soil Chemical Properties before and after the experiment
Treatment
ml/2kg soil pH
(H
2
O)
1:1
Org
C
gkg
-1
Total
N
gkg
-1
Avail
P
mgkg
-1
Mg
K
cmolkg
-1
Na
Exch
Acidity ECEC
Before trial
5.22
8.60
4.00
3.16
0.07
0.22
0.07
0.06
1.86
2.28
After trial
0 5.51a 5.70e 2.00c 1.79d 0.04d 0.18b 0.04b 0.04c 0.12c 0.42d
50 5.56a 19.10d 10.00b 2.37cd 1.40c 0.21ab 0.11a 0.08b 0.16bc 2.03c
100 5.33a 25.30c 13.00ab 2.91bc 1.92b 0.31ab 0.13a 0.10ab 0.20bc 2.66b
150 5.20a 32.90b 18.00ab 3.26b 2.24a 0.38a 0.13a 0.12a 0.24b 3.06a
200 5.18a 39.90a 20.00a 4.04a 2.28a 0.33a 0.15a 0.13a 0.36a 3.30a
Mean values with the same letters in the column are not significantly different from one another at P< 0.05
Table 3: Effect of palm oil mill effluent on maize (
Zea
mays L) number of leaves
Treatment Weeks after planting
ml/2kg soil 2 4 6 8
0
3.80
a
5.27
a
5.73
a
6.60
a
50 3.27
b
4.07
b
3.73
b
4.37
b
100 3.07
b
3.80
b
3.60
bc
4.20
b
150 3.00
b
2.87
c
2.60
cd
3.77
c
200 3.00
b
2.73
c
2.33
d
2.80
c
Mean values with the same letters in the column are not significantly
different from one another at P< 0.05
Table 4: E
ffect of palm oil mill effluent on height (cm)
of maize (Zea mays L)
Treatment Weeks after planting
ml/2kg soil 2 4 6 8
0
8.77
a
12.10
a
19.99
a
23.77
a
50 5.60
b
7.15
b
10.27
b
12.28
b
100 4.99
bc
6.13
bc
8.99
b
11.64
b
150 4.55
cd
5.37
c
6.13
c
9.25
bc
200 3.79
d
4.13
d
5.23
c
6.44
c
Mean values with the same letters in the column are not significantly
different from one another at P< 0.05
Table 5: Effect of palm oil mill effluent on leaf area (cm
2
) of maize (Zea mays L)
Treatments Weeks after planting
ml/5kg soil 2 4 6 8
0 148.41
a
439.48
a
853.00
a
1232.80
a
50 68.15
b
157.12
b
203.90
b
324.60
b
100 51.29
bc
108.10
c
201.30
b
299.30
b
150 42.17
bc
59.24
bd
53.24
c
138.40
b
200 37.18
c
45.57
d
25.35
c
60.20
b
Mean values with the same letters in the column are not significantly different from one another at P< 0.05
Table 6: Effect of palm oil mill effluent on stem girth (cm) of maize (Zea mays L)
Treatments Weeks after planting
ml/2kg soil 2 4 6 8
0 1.55
a
2.02
a
2.87
a
3.33
a
50 1.21
b
1.39
b
1.83
b
2.10
b
100 1.14
bc
1.30
b
1.75
b
2.03
b
150 1.09
bc
1.20
bc
1.36
c
1.69
bc
200
1.03
c
1.10
c
1.30
c
1.36
c
Mean values with the same letters in the column are not significantly different from one another at P< 0.0
Table 7: Effect of palm oil mill effluent on nutrient uptake by maize (
Zea
mays
L) (gkg
-
1
)
Treatment
ml/2 kg soil
N P K Ca Mg Na
0 0.13
a
0.02
a
0.13
a
0.03
a
0.01
a
0.01
a
50 0.11
a
0.01
a
0.02
b
0.02
b
0.01
a
0.003
b
100 0.08
b
0.01
b
0.02
b
0.03
a
0.01
a
0.003
b
150 0.02
c
0.01
b
0.003
c
0.01
c
0.004
ab
0.002
b
200 0.01
d
0.01
b
0.003
c
0.01
c
0.002
b
0.001
b
Mean values with the same letters in the column are not
significantly different from one another at P< 0.05