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Research Article
 

Agronomic Efficiency of Cowpea Varieties (Vigna unguiculata L. Walp) under Varying Phosphorus Rates in Lafia, Nasarawa State, Nigeria



I.M. Haruna and A. Usman
 
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ABSTRACT

Savanna soils of Nigeria are inherently low in nutrients (particularly nitrogen and phosphorus) thereby resulting in low yield of crops. To this end, field experiments were conducted at the Teaching and Research Farm of College of Agriculture Lafia in the Southern guinea savanna zone of Nigeria (08°30'N and 08°30'E, 18 m above sea level) during the rainy seasons of 2009, 2010 and 2011 to evaluate the yield and agronomic efficiency of cowpea varieties under varying phosphorus application rates. The experiment consisted of four levels of phosphorus in the form of single super phosphate (0, 30 and 60 kg P ha-1) and four varieties (DAN ILA, IAR-48, IT90K-277-1 and IT93K-452-1). The twelve treatment combinations were laid out in a randomized complete block design with three replications. The results obtained showed that number of pods per plant, pod yield per plant, seed yield per plant, number of seeds per pod, 100 seed weight and seed yield per hectare were significantly increased by the application of 30 kg P ha-1 in all the years of the experiment. Variety IT90K-277-1 consistently produced significantly, the highest values for all yield and yield characters measured. Agronomically, application of 30 kg P ha-1 was significantly more efficient than 60 kg P ha-1. Application of 30 kg P ha-1 to variety IT90K-277-1 produced significantly, the highest seed yield per hectare and is therefore recommended.

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  How to cite this article:

I.M. Haruna and A. Usman, 2013. Agronomic Efficiency of Cowpea Varieties (Vigna unguiculata L. Walp) under Varying Phosphorus Rates in Lafia, Nasarawa State, Nigeria. Asian Journal of Crop Science, 5: 209-215.

DOI: 10.3923/ajcs.2013.209.215

URL: https://scialert.net/abstract/?doi=ajcs.2013.209.215
 
Received: June 13, 2012; Accepted: December 18, 2012; Published: February 02, 2013



INTRODUCTION

Cowpea (Vigna unguiculata L. Walp.) is an important grain legume in the dry savanna of the tropics covering 12.5 million hectares with annual production of about 3.3 million tons (FAO, 2005). Nigeria is one of the world’s largest producer of cowpea with an average production of 2.92 million tons followed by Niger with 1.10 million tons and Myanmar with 0.15 million tons between 2006 to 2008 (http://faostat.fao.org/default.aspx). Despite the dramatic increase in cowpea production in Sub Saharan Africa, cowpea yields remain one of the lowest among all food legume crops, averaging at 450 kg ha-1 in 2006-08, which is half of the estimated yields in all other developing regions. Cowpea remains a leading legume in the recipe of the people in sub-Sahara Africa, supplying majority of the plant protein for human nutrition. The crop is essentially grown for the seed grains although the use of the green pods as vegetable cowpea is becoming important too. Cowpea also serve as a feed crop (fodder for animals) in many farming systems and fetch higher prices compared to cereals and are increasingly grown to supplement farmers’ incomes (Awodun, 2007). Despite the various uses to which the crop is put to, its yields are very low due to several constraints including poor soil and use of low yield variety of seeds as planting material.

Savanna soils are inherently low in nutrients particularly nitrogen and phosphorus (Haruna et al., 2011). Phosphorus (P) is among the most needed elements for crop production in many tropical soils. Phosphorus is critical to cowpea yield because it is reported to stimulate growth, initiate nodule formation as well as influence the efficiency of the rhizobium-legume symbiosis (Haruna and Aliyu, 2011). All growing plants require P for growth and development in significantly large quantity. Other workers have reported that phosphorus application influences the content of others nutrients in leaves and seeds (Muleba and Ezumah, 1985). The deficiency can be so acute in some soils of the savanna zone of western Africa that plant growth ceases as soon as the P stored in the seed is exhausted (Kang and Naggos, 1983).

High productive potential of cowpea has been reported by various workers through the use of organic and inorganic fertilizers (Abd El-Majeed et al., 2001; Madukwe et al., 2008; Singh et al., 2011) but efficiency of the applied fertilizer(s) is rarely documented. This work therefore seeks to evaluate the yield and agronomic efficiency of cowpea varieties under different phosphorus rates.

MATERIALS AND METHODS

Field experiment: Field experiments were conducted at the research farm of College of Agriculture Lafia in the Southern guinea savanna zone of Nigeria (08°30'N and 08°30'E, 18 m above sea level) on a sandy soil low in total nitrogen, available phosphorus and organic carbon (0.02%, 2.613 cmol kg-1 and 1.07%, respectively) during the rainy seasons of 2009, 2010 and 2011 to evaluate the yield and agronomic efficiency of cowpea varieties under varying phosphorus rates. The experiment consisted of four levels of phosphorus in the form of single super phosphate (0, 30 and 60 kg P2O5 ha-1) and four varieties (DAN ILA, IAR-48, IT90K-277-1 and IT93K-452-1). The twelve treatment combinations were laid out in a randomized complete block design with three replications.

The gross plot size was 18 m2 (4.5x4 m) while the net plot size was 9 m2 (3x3 m). The experimental area was disc-ploughed and harrowed twice to a fine tilt. This was then followed by ridging at 75 cm apart (between rows) and the field marked into plots and replications. The plots were separated by 1.0 m unplanted boarder while replications were separated by 2.0 m unplanted boarder. The four rates of phosphorus were incorporated into the plots according to treatment and field plan before sowing. Sowing was done on ridges 75 cm apart at 30 cm intra row spacing according to field plan and treatment combinations. Manual hoe weeding was done at 3, 6 and 9 WAS to keep the experimental plots weed-free.

Data collection: The crop was harvested at physiological maturity when the pods had turned yellow. Yield data per plant such as number of pods per plant was obtained by plugging all the pods from ten randomly selected plant samples and the mean recorded. Pod yield per plant was obtained by weighing all the pods plugged from ten selected plant samples and the mean recorded. Seed yield per plant was obtained by threshing the pods from the ten randomly selected plant samples, winnowed, the clean seeds weighed and the mean recorded. Number of seeds per pod was obtained by counting the seeds from twenty randomly selected pods from each net plot and the mean recorded. Pod yield per hectare was obtained by plugging and weighing all the pods in the net plot and the value so obtained was converted to per hectare basis. Seed yield per hectare was obtained by weighing the cleaned seeds from each net plot and the value so obtained was converted to per hectare basis. Hundred seed weight was obtained by weighing hundred randomly selected seeds from each net plot. Agronomic efficiency of the phosphorus fertilizer applied was calculated using the formula:

Image for - Agronomic Efficiency of Cowpea Varieties (Vigna unguiculata L. Walp) 
  under Varying Phosphorus Rates in Lafia, Nasarawa State, Nigeria

where, yield F is yield of fertilized cowpea (kg) and yield C is yield of the control cowpea to which no fertilizer was applied (kg).

Statistical analysis: The data collected were subjected to Analysis of Variance (ANOVA) as described by Snedecor and Cochran (1967) and significant differences among the treatment means were evaluated using Least Significant Difference.

RESULTS AND DISCUSSION

Table 1 shows the effects of phosphorus and variety on the yield characters of cowpea during the rainy seasons of 2009. Application of 30 kg P ha-1 produced significantly higher number of pods per plant, pod yield per plant, seed yield per plant, number of seeds per pod and 100 seed weight compared with the control in all the years of the experiment. Increasing the rate of P from 30 to 60 kg P ha-1, significantly decreased all the yield characters measured in 2009. Variety IT90K-277-1 produced significantly, higher number of pods per plant, pod yield per plant, seed yield per plant, number of seeds per pod and 100 seed weight than other varieties tested. This is followed by varieties IT93K-452-1, IAR-48 and DAN ILA in descending order.

Similarly, in 2010, application of 30 kg P ha-1 produced significantly higher number of pods per plant, pod yield per plant, seed yield per plant, number of seeds per pod and 100 seed weight than the control in all the years of the experiment. Increasing the rate of applied P from 30 kg P ha-1 to 60 kg P ha-1, significantly decreased all the yield characters measured in 2010 (Table 2). Variety IT90K-277-1 produced significantly, higher number of pods per plant, pod yield per plant, seed yield per plant, number of seeds per pod and 100 seed weight than other varieties tested. This is followed by varieties IT93K-452-1, IAR-48 and DAN ILA in descending order.

Table 1: Effects of phosphorus and variety on the yield attributes of cowpea during the rainy seasons of 2009 at Lafia
Image for - Agronomic Efficiency of Cowpea Varieties (Vigna unguiculata L. Walp) 
  under Varying Phosphorus Rates in Lafia, Nasarawa State, Nigeria
Means followed by different letter(s) within the same treatment group and column are statistically different at 5% level of probability

Table 2: Effects of phosphorus and variety on the yield attributes of cowpea during the rainy seasons of 2010 at Lafia
Image for - Agronomic Efficiency of Cowpea Varieties (Vigna unguiculata L. Walp) 
  under Varying Phosphorus Rates in Lafia, Nasarawa State, Nigeria
Means followed by different letter(s) within the same treatment group and column are statistically different at 5% level of probability

Table 3: Effects of phosphorus and variety on the yield attributes of cowpea during the rainy seasons of 2011 at Lafia
Image for - Agronomic Efficiency of Cowpea Varieties (Vigna unguiculata L. Walp) 
  under Varying Phosphorus Rates in Lafia, Nasarawa State, Nigeria
Means followed by different letter(s) within the same treatment group and column are statistically different at 5% level of probability

In 2011, application of 30 kg P ha-1 produced significantly higher number of pods per plant, pod yield per plant, seed yield per plant, number of seeds per pod and 100 seed weight than the control in all the years of the experiment. Increasing the rate of applied P from 30 kg P ha-1 to 60 kg P ha-1, significantly decreased all the yield characters measured in 2011 (Table 3). Variety IT90K-277-1 produced significantly, higher number of pods per plant, pod yield per plant, seed yield per plant, number of seeds per pod and 100 seed weight than other varieties tested. This is followed by varieties IT93K-452-1, IAR-48 and DAN ILA in descending order.

Application of 30 kg P ha-1 produced significantly higher seed yield of cowpea per hectare in 2009, 2010 and 2011 than the control and other level of applied P (Table 4). The highest seed yield of cowpea per hectare in all the years of the experiment was produced by variety IT90K-277-1 followed by varieties IT93K-452-1, IAR-48 and the DAN ILA.

Highly significant interaction occurred between applied P and the varieties tested (Table 5). The result of the interaction showed that application of 30 kg P ha-1 to variety IT90K-277-1 produced significantly higher seed yield per hectare than other rate of applied P to any variety. The least seed yield per hectare was produced by the local variety to which no P was applied.

Agronomic efficiency of phosphorus fertilizer applied to cowpea varieties indicated that application of 30 kg P ha-1 was more efficient (with an efficiency values of 23.1, 16.2 and 25.5 in 2009, 2010 and 2011, respectively ) compared to any other applied rates of P (Table 6).

Table 4: Effects of phosphorus and variety on the yield attributes of cowpea during the rainy seasons of 2009-2011 at Lafia
Image for - Agronomic Efficiency of Cowpea Varieties (Vigna unguiculata L. Walp) 
  under Varying Phosphorus Rates in Lafia, Nasarawa State, Nigeria
Means followed by different letter(s) within the same treatment group and column are statistically different at 5% level of probability, **Highly significant

Table 5: Interaction between phosphorus and variety on the seed yield (ha-1) of cowpea during the rainy seasons of 2009 - 2011 at Lafia
Image for - Agronomic Efficiency of Cowpea Varieties (Vigna unguiculata L. Walp) 
  under Varying Phosphorus Rates in Lafia, Nasarawa State, Nigeria
Means followed by different letter(s) within the same row and column are statistically different at 5% level of probability

Table 6: Agronomic efficiency of applied phosphorus on the seed yield of cowpea during the rainy seasons of 2009 - 2011 at Lafia
Image for - Agronomic Efficiency of Cowpea Varieties (Vigna unguiculata L. Walp) 
  under Varying Phosphorus Rates in Lafia, Nasarawa State, Nigeria
Means followed by different letter(s) within the same treatment group and column are statistically different at 5% level of probability, AE: Agronomic efficiency

This was followed by application of 60 kg P ha-1 with efficiency values of 21.7, 15.2 and 23.8 in 2009, 2010 and 2011, respectively.

The significant response of the yield and yield characters of cowpea measured to P application could be attributed to the very low content of the soil available P (as stated in the materials and methods above). It could also be attributed to the role of P in seed formation and grain filling (Haruna, 2011).

Table 7: Mean annual rainfall during the rainy seasons of 2009-2011 at Lafia
Image for - Agronomic Efficiency of Cowpea Varieties (Vigna unguiculata L. Walp) 
  under Varying Phosphorus Rates in Lafia, Nasarawa State, Nigeria
Source: Lafia Weather Station

The highest yield and yield characters recorded by the application of 30 kg P ha-1 and not the highest rate of applied P (60 kg ha-1) could probably be attributed to fact that 30 kg P ha-1 is the optimum rate of P required for higher yield in cowpea. This result is in conformity with the findings of Abd El-Majeed et al. (2001) and Singh et al. (2011).

The highest yield produced by variety IT90K-277-1 compared with other varieties tested could be due to its superior genetic composition which efficiently utilised the available resources for growth and development that eventually translated to higher yield and yield characters. The higher values recorded for yield and yield characters of cowpea varieties in 2011 than 2009 and 2010 could be attributed to the fact that in 2011, rainfall during the growing period (August to October) was uniformly distributed and there was no rain in the month of November that could damage the ripped pods thereby reducing the yield as it occurred in 2009 and 2010 (Table 7). The higher values of agronomic efficiency of applied P at 30 kg ha-1 could be attributed to the fact that, consistently that applied rate produced the highest yield in 2009, 2010 and 2011.

CONCLUSION AND RECOMMENDATION

From the foregoing, it can be concluded that application of 30 kg P2O5 ha-1 and planting of variety IT90K-277-1 produced the highest yield and yield characters of cowpea in all the years of the experiment. Application of 30 kg P ha-1 and planting of variety IT90K-277-1 seems to be ideal phosphorus rate and cowpea variety respectively for this agro-ecology and is therefore recommended.

REFERENCES

1:  Abd El-Majeed, Y.T., S.A. El-Shobaky and O.F. Dakhly, 2001. Effect of inoculation with Rhizobium mutants and foliar spray with ortho-phosphoric acid on growth and yield of cowpea. Proceedings of the 5th Arab Horticultural Conference, March 24-28, 2001, Ismailai, Egypt., pp: 75-85

2:  Awodun, M.A., 2007. Effect of sawdust ash on nutrient status, growth and yield of cowpea (Vigna unguiculata L. Walp). Asian J. Agric. Res., 1: 92-96.
CrossRef  |  Direct Link  |  

3:  FAO, 2005. Cow-pea production data base for Nigeria, 1990-2004. Food and Agriculture Organisation, http://www.faostat.fao.org/.

4:  Haruna, I.M., 2011. Dry matter partitioning and grain yield potential in sesame Sesamum indicum L.) as influenced by poultry manure, nitrogen and phosphorus at Samaru, Nigeria. J. Agric. Technol., 7: 1571-1577.
Direct Link  |  

5:  Haruna, I.M., L. Aliyu, O.O. Olufajo and E.C. Odion, 2011. Growth of sesame (Sesamum indicum L.) as influenced by poultry manure, nitrogen and phosphorus in Samaru, Nigeria. Am. Eurasian J. Agric. Environ. Sci., 4: 561-568.

6:  Haruna, I.M. and L. Aliyu, 2011. Yield and economic returns of sesame (Sesamum indicum L.) as influenced by poultry manure, nitrogen and phosphorus at Samaru, Nigeria. Elixir Agric., 39: 4884-4887.
Direct Link  |  

7:  Kang, B.T. and M. Naggos, 1983. Phosphorous re-quirement of cowpea. IITA Ibadan, Annual Report.

8:  Madukwe, D.K., I.E. Christo and M.O. Onuh, 2008. Effects of organic manure and cowpea (Vigna unguiculata (L.) walp) varieties on the chemical properties of the soil and root nodulation. Sci. World J., 3: 43-46.
Direct Link  |  

9:  Muleba, N. and H.C. Ezumah, 1985. Optimizing Cultural Practices for Cowpea in Africa. In: Cowpea Research Production and Utilization, Singh, S.R. and K.O. Rachie (Eds.). John Wiley and Sons Ltd., Chichester, UK., pp: 289-295

10:  Singh, A., A.L. Baoule, H.G. Ahmed, U. Aliyu and M.B. Sokoto et al., 2011. Influence of phosphorus on the performance of cowpea (Vigna unguiculata (L.) Walp.) Varieties in the sudan savanna of Nigeria. Agric. Sci., 2: 313-317.
Direct Link  |  

11:  Snedecor, G.W. and W.G. Cochran, 1967. Statistical Methods. 6th Edn., Iowa State University, Ames, IA, USA., Pages: 456

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