Bangladesh Agron. J. 2021, 24(1): 25-36 GROWTH AND YIELD OF COWPEA AS INFLUENCED BY DIFFERENT PHOSPHORUS LEVELS F.B. Putul1, A.R. Khan1, M.S. Hossain1, A. Mahmud1, Q.A. Khaliq1 and T. Ahmed2 1Department of Agronomy and 2Department of Agroforestry and Environment, Bangabandhu Sheikh Mujibur Rahman Agricultural University, Gazipur- 1706, Bangladesh. Corresponding Email: arif@bsmrau.edu.bd (Received: 15 January 2021, Accepted: 20 April 2021) Keywords: Legume, triple super phosphate, absolute growth rate, quality Abstract The experiment was carried out at the research field of the Department of Agronomy of Bangabandhu Sheikh Mujibur Rahman Agricultural University (BSMRAU), Gazipur during December 2016 to April 2017 to investigate the effect of different phosphorus levels (0, 30, 60 and 90 kg P ha-1) on the growth and yield of four selected cowpea genotypes (BARI Felon-1, A-06008, VI046192 and VI034386). The experiment was laid out in a factorial randomized complete block design with three replications. The results indicated that, among the genotype, BARI Felon-1 required minimum days to 1st (96 DAS) and 50% flowering (108 DAS) showing the highest absolute growth rate (0.71 g day-1), crop growth rate (23.69 g m-2 day-1), relative growth rate (0.047 g g-1 day-1), net assimilation rate (1.40 g m-2 day-1), leaf area index (6.68), SPAD value (51.03), seed length (0.71 cm) and breadth (0.54 cm). But the genotype, A-06008 gave the highest grain yield (0.62 t ha-1). Application of phosphorus at 90 kg ha-1 showed the highest leaf area index (6.67), SPAD value (50.98), pod length (14.33 cm), seed length (0.70 cm), seed breadth (0.50 cm) and grain yield (0.34 t ha-1). In terms of growth and yield, the cowpea genotype A-06008 showed the best performance at the phosphorus level of 90 kg ha-1. Introduction Cowpea (Vigna unguiculata L. Walp) is an important legume-pulse crop grown around the world which serves food for human consumption and fodder for livestock (Mfeka et al., 2019). The ripe seed on an average contains 22% protein, 1.4% fat, 59.1% carbohydrate, and 3.7% ash. The energy value is 340 kcal/ 100 g. Cowpea is suitable to grow at all regions of Bangladesh and grown as a short-duration crop in the rice based cropping systems after the harvest of transplant aman rice (William, 2016). Cowpea production is lower which is mainly due to the poor agronomic management as adopted to its production. Although cowpea is known to obtain most of its nitrogen requirements through symbiotic fixation, cowpea requires more phosphorus (P) than nitrogen (FAO, 2005). Basically, all legume crops need more P for growth and seed development (Sanginga et al., 2000). Phosphorus plays important role to cowpea yields as it stimulates growth, initiates nodule formation as well as accelerates the efficiency of the rhizobium-legume symbiosis (Haruna and Aliyu, 2011). Phosphorus stimulates root development and growth of young plants, giving them a good and vigorous start and control key enzyme reactions in the regulation of metabolic pathways. P favors increased leaf area and leaf area index by greater 26 Putul et al. growth of the leaf blade (Abayomi et al., 2008). P inputs either from soil reserves or from added fertilizer based on successful production systems of legumes (Brynes and Bumb, 1998). Acquisition of P fertilizer by crop depends on soil and plant properties. The research on genotypic variation of cowpea and the effect of P on the growth and development is little in Bangladesh. Therefore, this study was aimed to determine the effects of different levels of P with genotypic variation on the growth and quality of four selected cowpea genotypes. Materials and Methods A field experiment was conducted at the Agronomy Research Field of Bangabandhu Sheikh Mujibur Rahman Agricultural University, Gazipur 1706 from December 2016 to April 2017. The experimental site is located in Madhupur Tract under Agro Ecological Zone (AEZ) 28 at geographic coordinate between 24°09´ N latitude and 90°26´ E longitude with an elevation of 8.4 m from the sea level. The experiment consisted of two factors viz. four cowpea genotypes i.e. BARI Felon-1(G1), A-06008 (G2), VI046192 (G3) and VI034386 (G4) and four levels of phosphorus like P0(no phosphorus i.e. control), P30(30 kg P ha-1), P60(60 kg P ha-1) and P90(90 kg P ha-1). The experiment was laid out in a randomized complete block design (RCBD) with three replications. The unit plot size was 1.5 m1.5 m with a planting configuration of 30 cm10 cm. A fertilizer dose of 30 kg N, 30 kg K, 10 kg S, 2 kg Zn and 1 kg B ha-1 (BARC, 2012) was applied as basal during final land preparation in the form of urea, muriate of potash (MoP), sulfur, zinc sulphate and boric acid, respectively. Different levels of phosphorus were applied as treatment in soil in the form of triple super phosphate (TSP). All fertilizers were applied during final land preparation. Seeds of similar size were sown after treating with Bavistin @ 2 g kg-1 of seeds. A light irrigation was provided immediately after sowing to ensure uniform emergence. Plant protection measures were taken and intercultural operations were done whenever necessary. Days to 1st flower initiation and 50% flowering from each plot were recorded. Soil Plant Analysis Development (SPAD) value of leaf was recorded from 3 plants in each plot at 120 DAS using a SPAD meter (model: SPA-502, Minolta Camera Co. Ltd. Japan). For growth estimation, sampling was done at 40, 60, 80, 100 and 120 DAS. At maturity, 1 m2 area excluding border was selected to record the agronomic parameters and yield. Ten sample pods and ten sample seeds were used to measure pod length, seed length and breadth. Grain yield was recorded and adjusted at 12% moisture content. Absolute growth rate (AGR), crop growth rate (CGR), relative growth rate (RGR), net assimilation rate (NAR) and leaf area index (LAI) were calculated using the following formulae: 1 dayg 1 T 2 T 1 W 2 W AGR     1 dayg GA 1 1 T 2 T 1 W 2 W CGR      1 day 1 gg 1 T 2 T 1 LnW 2 LnW 1 T 2 T 1 W 2 W 1 W 1 RGR        1 day 2 mg 1 T 2 T 1 W 2 W 1 L 2 L 1 LnL 2 LnL NAR         Growth and Yield of Cowpea as Influenced by Different 27 area Ground leafof area Surface LAI  Where, W1 = Dry weight at time T1 (g), W2 = Dry weight at time T2 (g), GA = Ground area (m2), Ln = Natural logarithm, L1 = Leaf area at time T1 (m2), L2 = Leaf area at time T2 (m2). The recorded data for different plant parameters were subjected to statistical analysis. Statistix 10 software program was used to perform analysis of variation. The treatment means were compared using the least significant difference (LSD) test at 5% level of significance (Gomez and Gomez, 1984). Results and Discussion Days to 1st and 50% flowering Cowpea genotypes showed significant variation in number of days required to 1st flower initiation. The genotype G4 took maximum time (99 DAS) and the genotype G1 required the lowest time (96 DAS) for 1st flowering (Table 2). Phosphorus (P) fertilizer did not exert significant effect on days to 1st flowering. However, the highest number of days to 1st flowering (97 DAS) was obtained from P90 and the lowest (97 DAS) in P0 as presented in Table 2. Interaction between genotypes and P (Table 2) did not exert significant impact on days to 1st flowering. Days required to 50% flowering differed significantly in the genotypes tested. The maximum number of days required for 50% flowering (112 DAS) was observed in the genotype G4 and genotype G1 needed significantly the lowest number of days (108 DAS) as presented in Table 2. P fertilizer did not exert significant effect on days to 50% flowering (Table 2). The tested cowpea genotypes showed a marked variation in 1st and 50% flowering. The variation in 1st and 50% flowering is due to the inherent characters of the cowpea genotypes. Genotypic variation of flowering was also observed in common bean (Wondimu and Tana, 2017). Variation in 1st and 50% flowering due to application of different levels of phosphorus has also been reported in cowpea (Ayodele and Oso, 2014; Nkaa et al., 2014). Absolute growth rate Absolute growth rate (AGR) showed a significant variation in the different cowpea genotypes tested. AGR in genotypes G1, G2 and G4 increased progressively up to 100 DAS and in G3reached a peak at 80 DAS after that those genotypes gradually decreased. AGR decreased as the plant matured because of cessation of vegetative growth and senescence of leaves and AGR was decreasing after 80 DAS in genotype G3 and 100 DAS in genotypes G1, G2 and G4. Among the genotypes, G1 registered a maximum AGR (0.71 g day-1) and genotype G3 gave the lowest AGR (0.17 g day-1) at 100 DAS (Fig. 1a). Different P levels significantly influenced the growth of cowpea. AGR increased gradually with time reaching a peak at 100 DAS and declined afterwards till 120 DAS regardless of the P levels. Plants treated with P60 showed the highest AGR (0.56 g day-1) and P0 gave the lowest AGR (0.38 g day-1) at 100 DAS (Figure 2a). These results are in accordance with the findings of Seyed et al. (2011). The interaction of G3P90 gave the lowest (-0.15 g day-1) and G1P30 gave the highest AGR (0.95 g day-1) at 100 DAS (Table 1). Crop growth rate Crop growth rate (CGR) in different genotypes varied significantly as shown in Fig. 1b. CGR in genotypes G1, G2 and G4 increased progressively up to 100 DAS and G3 reached a peak at 80 DAS after that those genotypes gradually decreased (Fig. 1b). The highest CGR (23.69 g m-2 28 Putul et al. day-1) was obtained in the genotype G1 and the lowest (5.64 g m-2 day-1) in genotype G3. Different P levels significantly influenced the growth of cowpea. CGR increased gradually with time reaching a peak at 100 DAS and declined afterwards till 120 DAS regardless of the P levels. Similar result was reported that values of crop growth rate are normally low during early growth stages and increase with time, reaching maximum values at about the time of flowering (Fageria et al., 2006). Application of P enhanced leaf growth, reduced leaf senescence and helped intercept more radiation resulting in greater amount of photosynthesis. Among the levels of P, P60 registered a maximum CGR (18.56 g m-2 day-1) while P90 gave the lowest CGR (12.82 g m-2 day-1) at 100 DAS (Fig. 2b). Ehsan et al. (2017) also found the highest CGR applying 60 kg Pha-1at all the growing period of mungbean. The interactions between genotypes and levels of P also showed significant variation in crop growth rate throughout the growing periods (Table 1). At 100 DAS the interaction of G1P30 gave the highest (31.79 g m-2 day-1) and G3P60 gave significantly the lowest CGR (3.14 g m-2 day-1). Relative growth rate The relative growth rate (RGR) gives the efficiency of current dry matter to produce future dry matter. RGR was high in early of the growth period and showed decreasing trend as the crop advanced in age (Fig. 1c). RGR decreases as the plant ages due to the fact that an increasing part of the plant is structural rather than metabolically active tissue and as such does not contribute to growth (Chattjrvedi et al., 1980). Among the genotypes tested, the highest RGR was 0.08 g m-2 day-1 in genotype G4 and the lowest in genotype G2 (0.05 g g-1 day-1) at 60 DAS. The RGR was significantly influenced by different P levels. However, irrespective of different P levels, RGR was pronounced early in the season and showed a decreasing trend as the crop advanced towards maturity (Fig. 2c). Similar decreasing trend of RGR was also reported by Ehsan et al. (2017) in mungbean. P90 registered maximum RGR (0.07 g g-1 day-1) while plants treated with P0 gave the lowest RGR (0.05 g g-1 day-1) at 60 DAS in this study. Again, the interaction effect of genotypes and different levels of P on RGR was found significant. The interaction of G4P90 gave the highest RGR (0.09 g g-1 day-1) and G2P0 gave the lowest (0.01 g g-1 day-1) at 60 DAS (Table 1). Net assimilation rate Net assimilation rate (NAR) is a value that relates plant productivity to plant size. It is useful as a measure of the photosynthetic efficiency of plants and reflects the balance of photosynthetic rate against respiration and tissue loss rates (Quero et al., 2006). In the present study, different genotypes showed significant effect on NAR under different P levels (Fig.1d). NAR increased progressively from 60 DAS to 100 DAS after that the trend decreased in all the studied genotypes except G3. NAR in the genotype G3 increased gradually from 60 DAS to 80 DAS after that it decreased (Fig. 1d). At 100 DAS, the genotype G1 gave the highest NAR (4.10g m-2 day-1) and G3 genotype gave the lowest (1.40 g m-2 day-1). Different levels of P showed significant effect on NAR. NAR increased progressively up to 100 DAS in all levels of P after that the trend decreased gradually (Fig. 2d). At 100 DAS, P60 gave the highest NAR (3.54 g m-2 day-1) and P90 gave the lowest (2.15 g m-2 day-1). Likely, the interaction between genotypes and different P levels showed significant impact on NAR. The interaction of G4P60 gave the highest (5.96 g m-2 day-1) and G3P60 gave the lowest (0.75 g m-2 day-1) NAR at 100 DAS (Table 1). NAR decreased during the growing season as more and more leaves were fully or partially shaded. Also, the decrease in NAR with plant age may be due to older average leaf age which resulted in lower photosynthetic efficiency. Growth and Yield of Cowpea as Influenced by Different 29 Leaf area index Leaf area index (LAI) depends on number of leaves and leaf expansion in a plant. Leaf area is made up of the total green area of emerged leaves (Keating and Carbery, 1993). It was indicated that leaf area index, leaf area duration and dry matter accumulation during the reproductive period strongly influence the yield components (Liu et al., 2004). Greater leaf area is necessary to have superior yield components in grain legumes (Muchow, 1985). Here, LAI increased progressively up to 100 DAS in all cowpea genotypes after that it gradually decreased (Fig. 1e). At 100 DAS, the highest LAI (6.68) was obtained in the genotype G1 and the lowest (5.03) in genotype G3. The variation in LAI among the genotypes might be due to genetic character of the genotypes. Greenness duration The greenness of different genotypes at 120 DAS was measured by SPAD meter. The highest SPAD value (51.03) was obtained in the genotype G1 and the lowest (46.48) in G3 (Fig. 1f). The general trend was an increase in SPAD value with the increase in P levels except in P60 though the variation wasn’t significant. At 120 DAS, the highest SPAD value (50.98) was recorded at P90 and the lowest (47.19) at P60 (Fig. 2f). The interaction of genotypes and P levels did not exert significant impact on SPAD value of cowpea (Table 1). 30 Putul et al. Fig. 1. Variation in (a) absolute growth rate (AGR), (b) crop growth rate (CGR), (c) relative growth rate (RGR), (d) net assimilation rate (NAR), (e) leaf area index (LAI) and (f) SPAD values of cowpea genotypes over time. Vertical bars indicate LSD (0.05). (c) (b) (d) (e) (f) (a) Growth and Yield of Cowpea as Influenced by Different 31 Fig. 2. Variation in (a) absolute growth rate (AGR), (b) crop growth rate (CGR), (c) relative growth rate (RGR), (d) net assimilation rate (NAR), (e) leaf area index (LAI) and (f) SPAD values due to different levels of P over time in cowpea genotypes. Vertical bars indicate LSD (0.05). (a) (d) (b) (c) (e) (f) 32 Putul et al. Table 1. Interaction effect of cowpea genotypes and levels of P on absolute growth rate (AGR), crop growth rate (CGR), relative growth rate (RGR), net assimilation rate (NAR), leaf area index (LAI) and SPAD value over time Interaction (G×P) AGR at different DAS CGR at different DAS RGR at different DAS NAR at different DAS LAI at different DAS SPAD value 60 80 100 120 60 80 100 120 60 80 100 120 60 80 100 120 40 60 80 100 120 120 G1P0 0.09 0.34 0.74 -0.25 3.06 11.17 24.76 -8.42 0.07 0.07 0.05 -0.01 2.36 3.05 4.63 -1.63 0.48 2.76 4.73 6.02 4.38 49.93 G1P30 0.12 0.32 0.95 -0.12 3.84 10.54 31.79 -4.13 0.07 0.06 0.06 0.00 2.48 2.76 5.63 -0.71 0.75 2.78 5.10 6.24 5.37 52.47 G1P60 0.11 0.24 0.59 0.38 3.56 7.95 19.51 12.59 0.06 0.05 0.05 0.02 2.10 1.93 3.37 2.10 0.74 3.26 5.14 6.48 5.55 52.73 G1P90 0.09 0.36 0.56 0.31 2.86 12.01 18.69 10.41 0.05 0.07 0.04 0.01 1.46 2.43 2.74 1.54 0.72 4.17 5.80 7.97 5.69 56.21 G2P0 0.03 0.25 0.28 0.19 0.95 8.45 9.35 6.25 0.01 0.05 0.03 0.01 0.77 2.63 1.99 1.10 0.47 2.57 3.97 5.51 5.84 45.10 G2P30 0.13 0.19 0.54 -0.08 4.32 6.28 18.01 -2.75 0.07 0.04 0.05 0.00 3.08 1.63 3.35 -0.55 0.48 3.09 4.71 6.09 4.03 49.87 G2P60 0.08 0.22 0.66 -0.27 2.74 7.41 21.95 -9.01 0.06 0.05 0.05 -0.02 2.53 2.61 4.09 -1.72 0.62 1.74 4.34 6.56 4.08 50.23 G2P90 0.10 0.42 0.44 0.04 3.35 13.95 14.80 1.41 0.06 0.07 0.03 0.00 2.16 3.45 2.32 0.23 0.73 2.83 5.57 7.24 5.07 51.70 G3P0 0.06 0.14 0.16 0.19 1.95 4.75 5.32 6.39 0.06 0.05 0.03 0.02 2.94 2.34 1.40 1.83 0.31 1.22 3.15 4.54 2.64 48.87 G3P30 0.05 0.24 0.27 0.07 1.50 8.01 9.04 2.35 0.04 0.07 0.03 0.01 2.97 5.26 2.27 0.49 0.39 0.64 2.98 5.21 4.46 48.20 G3P60 0.05 0.21 0.09 0.25 1.80 7.11 3.14 8.41 0.06 0.07 0.01 0.03 2.62 3.58 0.75 1.79 0.46 0.98 3.53 4.96 4.45 39.57 G3P90 0.07 0.09 0.15 0.16 2.36 3.10 5.05 5.26 0.08 0.04 0.03 0.02 2.26 1.29 1.20 1.21 0.57 1.74 3.21 5.40 3.45 49.30 G4P0 0.09 0.21 0.73 -0.31 3.16 6.87 24.18 -10.30 0.08 0.05 0.06 -0.02 3.11 2.05 4.62 -2.09 0.40 2.07 5.07 5.41 4.50 49.300 G4P30 0.10 0.30 0.25 0.21 3.46 9.94 8.22 7.09 0.08 0.06 0.02 0.01 2.42 2.97 1.86 1.61 0.58 2.87 3.88 5.02 3.84 44.00 G4P60 0.07 0.36 0.89 -0.18 2.40 11.93 29.63 -5.89 0.06 0.07 0.05 -0.01 1.92 3.62 5.96 -1.18 0.66 2.13 4.83 5.12 4.91 46.23 G4P90 0.12 0.16 0.38 0.34 3.86 5.34 12.75 11.44 0.09 0.04 0.04 0.02 2.33 1.34 2.33 2.01 0.72 3.18 4.93 6.05 5.33 53.93 LSD (0.05) 0.00 0.00 0.00 0.00 0.10 0.14 0.13 0.10 0.00 0.00 0.00 0.00 0.13 0.10 0.07 0.05 0.02 0.09 0.13 0.11 0.13 NS CV (%) 2.09 0.99 0.47 3.05 2.09 0.99 0.47 3.05 4.02 1.31 0.83 2.40 3.44 2.24 1.43 7.42 1.56 2.36 1.71 1.08 1.65 11.37 DAS = Days after sowing Growth and Yield of Cowpea as Influenced by Different 33 Different levels of P significantly influenced the LAI (Fig. 2e). Regardless of the levels of P, LAI increased progressively up to 100 DAS in all P treatments after that it gradually decreased (Fig. 2e). Plants treated with P90 showed the highest LAI (6.67) and P0 showed the lowest (5.37) at 100 DAS. Variation in LAI due to the application of different levels of P in cowpea was also reported in several studies (Ayodele and Oso, 2014; Nkaa et al., 2014). The interaction effect of genotypes and levels of P was also significant on LAI throughout the growth period (Table 1). At 100 DAS the best interaction was G1P90 which gave the highest (7.97) and G3P0gave the lowest (4.54) LAI. Increase in LAI due to increasing rate of applied P might be attributed to well- developed root system of the genotypes favored by P uptake. These findings were also supported by the results found in soybean (Singh and Bansal, 2000). Pod length Pod length was significantly influenced by the variation in genotypes and different levels of P. The longest pod (18.31 cm) was recorded in genotype G4 and the shortest (8.59 cm) in G3 (Table 2). Application of different levels of P showed significant influence on pod length. The P90 had the longest pod (14.33 cm) and P30 had the shortest (13.94 cm) as presented in Table 10. Nkaa et al. (2014) also showed an increasing pod length due to P application in cowpea. The interaction of genotypes and different levels of P showed significant impact on pod length. The highest pod length (19.1 cm) was measured from the G4P30 interaction and the shortest (7.78 cm) from G3P30 (Table 2). Seed length and breadth Seed length and breadth in cowpea genotypes varied significantly as shown in Table 2. The average highest seed length and breadth (0.71 cm and 0.54 cm, respectively) were obtained in the genotype G1 and the lowest in G3 (0.62 cm and 0.43 cm, respectively). Application of different levels of P also showed significant influence on seed length and breadth. The average lowest seed length and breadth (0.67 cm and 0.47 cm, respectively) were obtained in P0 and the highest (0.70 cm and 0.50 cm, respectively) in P60 and P90 (Table 2). The interaction between genotypes and levels of P showed significant effect on seed length and breadth (Table 2). The G1P60 interaction gave the highest seed length and breadth (0.77 cm and 0.60 cm, respectively) and G3P0, G3P30 and G3P60 had the lowest (0.60 cm and 0.40 cm, respectively). Grain yield Both genotypes and P levels exerted significant influence on grain yield. Genotypic variations in grain yields were evident (Table 2). The genotype G2 gave significantly the highest grain yield (0.62 t ha-1) and G4 gave the lowest (0.03 t ha-1). Grain yield also increased significantly with increasing level of P. P0 obtained the lowest (0.27 t ha-1) and P90 obtained the highest (0.34 t ha-1) grain yield (Table 2). Moreover, the interaction of genotypes and different P levels exerted significant effect on grain yield (Table 2). G2P90 gave the highest grain yield (0.69 t ha-1) and G4P30 gave the lowest (0.01 t ha-1). The tested cowpea genotypes varied significantly in their grain yield though different P levels exerted significant influence on it. Grain yield increased with the increasing level of P. This might be due to the fact that P90 contributed to the highest NAR, LAI, greenness duration, pod length, seed length and breadth. These results are in accordance with the findings obtained by Nkaa et al. (2014) and Singh et al. (2011). 34 Putul et al. Table 2. Days to 1st flowering, days to 50% flowering, pod length, seed length, seed breadth and grain yield of cowpea genotypes as influenced by different levels of P Genotypes (G) Days to 1st flowering (DAS) Days to 50% flowering (DAS) Pod length (cm) Seed length (cm) Seed breadth (cm) Grain yield (t ha-1) G1 95.67 107.75 14.83 0.71 0.54 0.51 G2 96.67 108.50 14.70 0.70 0.50 0.62 G3 97.67 109.08 8.59 0.62 0.43 0.04 G4 99.25 112.08 18.31 0.70 0.50 0.03 LSD (0.05) 0.44 0.73 1.00 0.02 0.02 0.01 CV (%) 0.55 0.80 8.89 3.87 5.87 3.32 Phosphorus (P kg ha-1) Days to 1st flowering (DAS) Days to 50% flowering (DAS) Pod length (cm) Seed length (cm) Seed breadth (cm) Grain yield (t ha-1) P0 97.17 109.08 14.02 0.67 0.47 0.27 P30 97.22 109.50 14.13 0.68 0.50 0.28 P60 97.25 109.33 13.9 0.70 0.50 0.32 P90 97.42 109.50 14.33 0.70 0.50 0.34 LSD (0.05) NS NS 1.04 0.02 0.02 0.01 CV (%) 0.55 0.80 11.84 3.87 5.87 3.32 Interaction (G×P) Days to 1st flowering (DAS) Days to 50% flowering (DAS) Pod length (cm) Seed length (cm) Seed breadth (cm) Grain yield (t ha-1) G1P0 95.67 107.67 14.80 0.67 0.47 0.39 G1P30 95.67 108.00 15.62 0.72 0.60 0.59 G1P60 95.67 107.67 14.19 0.77 0.60 0.49 G1P90 95.67 107.67 14.72 0.70 0.50 0.56 G2P0 96.67 108.00 14.55 0.70 0.50 0.65 G2P30 97.00 109.00 14.04 0.70 0.50 0.49 G2P60 96.33 108.33 14.89 0.70 0.50 0.67 G2P90 96.67 108.67 15.31 0.70 0.50 0.69 G3P0 97.33 109.00 8.68 0.60 0.40 0.03 G3P30 97.67 108.67 7.78 0.60 0.40 0.02 G3P60 97.67 109.00 8.42 0.60 0.40 0.09 G3P90 98.00 109.67 9.46 0.67 0.50 0.04 G4P0 99.00 111.67 18.1 0.70 0.50 0.02 G4P30 99.33 112.33 19.1 0.70 0.50 0.01 G4P60 99.33 112.33 18.25 0.70 0.50 0.03 G4P90 99.33 112.00 17.83 0.70 0.50 0.08 LSD (0.05) NS NS 2.09 0.04 0.05 0.02 CV (%) 0.55 0.80 11.84 3.87 5.87 3.32 Conclusions Growth and quality parameters of four cowpea genotypes in response to four phosphorus fertilizer application levels were evaluated. Growth and quality of cowpea were influenced by different phosphorus levels though genotypic variation was conspicuous. The results revealed that among the four selected cowpea genotypes, the highest absolute growth rate, crop growth rate, relative growth rate, leaf area index, greenness duration and seed length and breadth were obtained from BARI Felon-1, but the genotype A-06008 gave the highest grain yield (0.62t ha-1). Plants with phosphorus 90 kg ha-1 gave the highest leaf area index, greenness duration, Growth and Yield of Cowpea as Influenced by Different 35 pod length, seed length, breadth and grain yield (0.34 t ha-1). The genotype A-06008 gave the highest grain yield (0.69 t ha-1) at P 90 kg ha-1. References Abayomi, Y.A., T.V. Ajibade, O.F. Sammuel and B.F. Sa´adudeen. 2008. Growth and yield responses of cowpea (Vignaunguiculata (L.) Walp) genotypes to nitrogen fertilizer (N) application in the Southern Guinea Savanna zone of Nigeria. Asian J. Plant Sci. 7(2): 170- 176. 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