EFFECT OF SALINITY ON GERMINATION, GROWTH ...

NIGERIAN ANNALS OF NATURAL SCIENCES, VOLUME 15 (1) 2015 (pp 018 –023) ISSN: 1115-2702 @ www.nansjourmal.org

EFFECT OF SALINITY ON GERMINATION, GROWTH AND YIELD PERFORMANCE OF COWPEA (Vigna unguiculata L. Walp.) IN MUBI, NIGERIA Mshelmbula, B.P.1, Zakariya, R. 1, Mensah J.K.2 and Ikhajiagbe, B.3 1

Department of Biological Sciences, Adamawa State University Mubi, P.M.B 25, Mubi, Nigeria. 2 Department of Botany Ambrose Alli University Ekpoma, Edo State, Nigeria. 3 Department of Plant Biology and Biotechnology, University of Benin, Benin City, Nigeria. *Corresponding author: Email: [email protected] ABSTRACT

Salinity remains a threat to agricultural crop productions, especially in cowpea production in many parts of the world. This research work was conducted to evaluate the impact of salt on germination, growth and yield performance of cowpea in Mubi, Nigeria. Different NaCl concentrations (0.25, 1.0, 2.0 and 2.50g/L) were tested on the parameters as experimental treatments, while the control contained only water without any NaCl additive. Data were collected on germination, growth and yield performance of cowpea under the salt stress, and were subjected to One-way analysis of variance, and the treatment means were compared using Duncan’s New Multiple Range (DMR) Test at 5% (P>0.05) level of significance. The results obtained showed that the germination of cowpea seeds, growth and yield were highly affected by salinity at all levels of treatments when compared with the control. In conclusion, therefore, the results further confirmed the deterrent of salinity to cowpea production especially in Mubi, Nigeria. Key words: Cowpea, germination, salinity, yield.

INTRODUCTION Cowpea (Vigna unguiculata L. Walp.) is widely cultivated in a range of ecologies especially in the savannah regions and in tropics and sub-tropics (Singh, 2007). It is one of the most important food legume crops in the semi arid tropics covering Asia, Africa, Southern Europe and Central America (Fazal et al., 2012). Cowpea is also an important food crop in west and Central Africa (Victor et al., 2009). High protein content of cowpea, ranging between 20 to 28% makes it an important supply to the diet of many African people (Giami et al., 2001). Cowpea also contributes to the soil nitrogen status through symbiotic N2 fixation, thereby enhancing soil fertility (Martins et al., 2003). Salinity is one of the most serious factors limiting crop production, especially the sensitive ones (Zhang and Hodson, 2001). High soil salinity affects agricultural production in large propotion in the world territorial areas (Zhang and Hodson, 2001). Munns (2002), reported that salinity reduced the ability of plants to take up water, leading to growth reduction as well as metabolic changes similar to those caused by water stress. Similarly, Alan et al. (2004) and Taffouo et al. (2004) reported that high salt concentration in roots, affects the growth and yield of many important crops. The salinity reduced the crop yield

by upsetting water and nutritional balance of plant. Salinity is a wide spread environmental stress for crop plant in arid coastal regions of the world (Patel et al., 2010). Due to increasing salt salinity, large areas of arable land are being removed from crop production every year (Epstein et al., 1980). The use of saline irrigated water and application of fertilizer are the main factors for increasing soil salinity (Epstein et al., 1980). Excess salinity in the soil water can decrease plant availability and can cause plant stress (Agassi et al., 1981). High level of soil salinity can significantly inhibit seed germination and seedling growth, due to the combined effects of high osmotic potential and specific ion toxicity (Grieve and Suarez, 1997). For cowpea, quite a number of reports have been reported on the effects of salinity on the growth of cowpea. Silva et al. (2003), stated that salinity levels adversely affected growth of cowpea, while testing 25 genotypes of cowpea at different salinity levels; Amador and Dieguez (2007), reported that the weight of sodium chloride pre-treated seeds of cowpea decreased significantly at increased salinity. Filho (2008), observed that lengths of the main roots and shoots of cowpea decreased to 23% and 44% respectively when treated

Nigerian Annals of Natural Sciences

with 100m sodium chloride. Because of the high economic contributions of cowpea to both human and livestock all over the world and particularly in Nigeria, there is need to know the salt tolerance of cowpea grown especially in Mubi, Nigeria. Hence, this research was therefore designed to evaluate the effects of salinity on the germination, growth and yield performance of cowpea in Mubi, Nigeria.

MATERIALS AND METHODS Study Area The study area is Mubi. Mubi is located in the North Eestern part of Nigeria between latitude 10º 14’N and 10º 18’ N of the equator and longitude 13º 14’ E and 13º 19’E of the Greenwich meridian. It occupies a land of about` 725.85km with an estimated population of about 300,000 people. The area has tropical climate with an average temperature of 32ºC and lies within the Sudan savannah vegetation zone in Nigeria. The area has an average relative humidity from 28%-45% and annual rainfall of about 1056mm (Adebayo and Tukur, 1999).

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water (1liter) without any additive was also measured and was used as control. All the treatments including the control (untreated) were replicated 5 times. These were labeled as L1, L2, L3, L4, and L5. The soil filled pots (five replicates for each treatment), were spaced 15cm apart, within each row. Four (4) seeds randomly selected were sown in each of the polythene bags including the control portion. The seeds were maintained on non-saline nutrient solution until they reached the first trifoliate leaf stage (about 3 weeks after planting). Thereafter, constant irrigation using the treatments was done every morning and evening throughout the experiment.

Data Collection Data were collected on the following observations:

Number of Days to Seed Germination Germination of the cowpea seeds sown in all the experimental pots were subsequently noted, until they were fully germinated.

Collection of Materials Clean cowpea seeds (‘Efe brown’) were obtained from a farmer around Tudun-Wada area of Mubi, and were kept in the laboratory of Adamawa State University Mubi, located in lokuwa area of Mubi. Thereafter, the seeds were treated with Dress Force (20% imidacloprid, 20% metalaxyl-M, 20%Ws Tebuconazole), until it was ready for planting. The soil that was used (mixture of sandy, loamy, and clay soil),was collected around the Botanical Garden of the Adamawa State University Mubi, as the area has not been cultivated for a very long time ,and was expected to be highly fertile. Top soil (0-10cm) was collected for use. The soil was sun dried to constant weight, and thereafter, 5kg of soil was measured into palm nursery poly bags of 30cm in height and 15cm in diameter. These were perforated at the bottom. The bags were placed in the screen house at a spacing of 60cm x 30cm, as proposed by Okeleye et al. (1999). An analytical reagent sodium chloride (NaCl = 58.44) was obtained from a chemical store in Yola, Adamawa State.

Percentage (%) of Seed Germination The percentage of the seeds germinated was calculated using the formula as shown:

n x 100 N Where n = Number of seeds germinated N = Total number of seeds planted (=4)

Number of Leaves per Plant Number of leaves per plant after germination was continuously counted on weekly basis.

Plant Height The height of the plants in all the experimental pots was measured with the aid of a ruler (30cm). This was done on weekly basis for ten (10) weeks.

Method of Application 0.25g, 1.00g, 2.00g and 2.50g of sodium chloride were measured and diluted in one liter of tap water each. The mixture was stirred vigorously to ensure a total and complete dilution of the NaCl reagent. These were stored in bottles with screw cap top. Another portion of the tap

Number of Root Nodules The distribution of root nodules within the soil profile was determined by uprooting the cowpea plants and number of nodules counted. This was done immediately after


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Table 1. Effect of salinity on germination of cowpea.

Treatment [NaCl (g/l)] 0.00 (control) 0.25 1.0 2.0 2.5

No. of days to germination a 3.60±0.55 b 4.70±0.84 b 5.33±0.76 b 5.38±1.11 c 6.00±0.71

% of seeds germinated a 75.00±17.68 b 45.00±20.92 b 35.00±33.54 b 30.00±20.92 b 40.00±28.50

Values are means of five replicates. Means carrying the same superscripts are not significantly different from each other at P>0.05 probability level.

harvest. Estimate of root size was determined with the aid of a caliper. Number of Days to First Flowering

germination. The control plants germinated earlier (3.60±0.55) than the saline treated plants. The germination of seeds in the salt treated pots delayed with increasing salinity, as follows: 0.00>0.25>1.00>2.00>2.50

The experiment was also noted for first flowering in all the plants between 7-10 weeks. The mean of the results was also calculated and recorded.

At 2.50 concentrations, cowpea seeds germination recorded the highest delay.

Number of Days to First Pod Formation

Percentage (%) of Seeds Germinated

This is the number of days after planting, taken for the plants to produce its newest viable pod. This was subsequently noted, and recorded.

Data analysis showed that different Nacl concentrations significantly affected the percentage germination/number of days to germination (Table 1). The control treatment germinated highest with about 75% (75.00±17.68) of seeds germination than the NaCl treatments at all concentrations. In this parameter, the salt treated plants at all concentrations did not differ significantly from each other when compared with the control (untreated) at P>0.05 probability level (Table 1).

Number of days to first pod maturity The number of days taken by each cowpea plant to produce

its first matured pod was also noted and recorded. Number of Pods per Plant

Number of Leaves per Plant After harvest, the number of pods formed on each cowpea plant was counted.

Number of Seeds per Pod Number of seeds in each pod was counted for every cowpea plant and recorded.

Number of leaves per plant was significantly affected by Nacl at different concentrations when compared with the control (untreated). The control had maximum leaves per plant (39.40±3.65), followed by 0.25 (32.33±4.93), 1.00 (24.25±1.06), 2.50 (19.67±1.16) and 2.00 (19.00±0.00) (Table 2). Plant Height

Data Analysis Data collected were subjected to one-way analysis of variance, and Duncan’s New Multiple Range (DMR) Test was used to separate the mean differences at 5% level of significance. RESULTS

Table 2 also shows the effect of Nacl on the height of plant stems grown under different salt stress. Nacl at all concentrations significantly affected the stem height of plants. The control recorded the longest stem height (124.00±15.33), followed by cowpeas treated with Nacl at 0.25 (86.67±18.55), 2.00 (73.75±8.84), 1.00 (73.25±8.13) and 2.50 (65.57±5.87) respectively.

Number of Days to Germination

Number of root nodules per plant

Table 1 shows the effect of salinity on cowpea seed

The number of root nodules also varies among the


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Table 2. Effect of salinity (Nacl) on the growth performance of cowpea.

Treatment (Nacl (g/l)) 0.00 (Control) 0.25 1.00 2.00 2.50

No. of leaves per plant c 39.40±3.65 b 32.33±4.93 a 24.25±1.06 a 19.00±0.00 a 19.67±1.16

Plant height b 124.00±15.33 a 86.87±18.55 a 73.25±8.13 a 73.75±8.84 a 65.57±5.87

No. of root nodules b 21.80±3.40 a 14.50±1.80 ab 18.40±1.27 ab 16.50±4.95 ab 18.68±1.16


Table 3. Effect of salinity on the yield components of cowpea.

Treatment (Nacl (g/l)) Control (0.00) 0.25 1.00 2.00 2.50

No. of days to flowering a 59.20±2.93 ab 60.43±4.03 ab 61.25±1.77 b 67.25±0.35 ab 65.88±5.11

No. of days to 1 pod formation a 67.70±2.86 a 67.23±3.22 a 70.75±2.48 a 74.00±1.41 a 72.33±2.52

st

No. of days to 1 pod maturity a 82.10±3.05 ab 84.10±2.01 bc 86.50±0.71a c 90.50±2.12 bc 87.33±1.16

st

No. of pods per plant d 6.50±1.23 cd 4.73±0.87 bc 4.30±0.42 ab 2.75±0.35 a 1.97±0.65

No. of seeds per pod b 6.62±0.67 b 6.03±0.40 b 5.20±1.13 a 3.45±1.20 a 2.37±1.03


treatment. In a similar trend, the control had the maximum (21.80±3.40), but was not significantly different from 1.00 (18.40±1.27), 2.00 (16.50±4.95), and 2.50 (18.68±1.16) at P>0.05 probability level (Table 2). Among the Nacl treatments, 0.25 suppressed the growth of root nodules to the least (21.80±3.40).

Number of Days to Flowering Table 3 shows the number of days to flowering. The result showed that different concentrations of Nacl significantly affected the period of flowering in the cowpea plants. The control untreated yielded flowers earlier than the plants treated with Nacl. Among the plants treated with Nacl, 2.00 recorded the highest value (67.25±0.35).

was shown. The control plants recorded the earliest pod maturity before the cowpeas treated with Nacl. 2.00 delayed maturity more 0.25, 1.00, and 2.50 treatment concentrations in the following order: 2.00>2.50.1.00>0.25>control (90.50±2.12>87.33±1.16>86.50±0.71>84.10±2.01>82.10 ±3.05 respectively) Number of Pods per Plant In Table 3, different concentrations of salinity (Nacl) have significantly affected the number of pods per plant. At the control level, maximum (6.50±1.23) number of pods per plant was achieved and decreases significantly with increased salinity in the following order:

Number of Days to First Pod Formation Control>0.25>1.00>2.00>2.50 There is no significant difference between the control (untreated) and the treated plants at various concentrations of Nacl in the number of days to first pod formation (Table 3). 0.25 concentration recorded the earliest pod at 67.23±3.22 and 2.00 concentration recorded the highest at 74.00±1.41, but did not differ significantly from the other treatments at P>0.05 probability level. Number of Days to First Pod Maturity Also, in Table 3, the number of days to first pod maturity

Number of Seeds per Pod The number of seeds per pod followed a similar trend with the number of pods per plant (Table 3). The control recorded the maximum number of seeds per pod (6.60±0.67) and decreases with increased concentrations in the following order: Control(6.62±0.67)>0.25(6.03±0.40)>1.00(5.20±1.13)>2. 00(3.45±1.20) >2.50 (2.37±1.03) respectively.


DISCUSSIONS In Table 1, the effect of salinity on germination showed that number of days to germination increases with increased salinity. This means that seed germination delayed with enhanced salinity. This coincides with the findings of Amado et al. (2006), Amador and Dieguez (2007), Mahmood et al. (2009), Muhammad and Hussain (2010), and Ghaloo et al. (2011), who reported that increase in Nacl concentrations increases the days to germination. This could also be that the plumule and radial growth decreases at high levels of salinity. Percentage (%) of seed germination increases significantly (P0.05) by salinity (Table 3). This present finding agrees with the findings of Ahmed (2009) who earlier reported reduced flowers, pods and seeds under salinity stress. The significant decrease in yield observed in the salt treated cowpeas would be related to a significant reduction of the foliar chlorophyll contents and potassium concentrations in saline medium (Victor et al., 2009). Conclusively, the salinization of agricultural soils is a worldwide concern, especially in irrigated land where water is the salt transporting agent through soil profile. In this study, the results obtained further confirmed the deterrent of salinity to cowpea production especially in reducing the yield components.

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