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Groundnut ( Arachis hypogaea ), cowpea ( Vigna unguiculata ) and soybean ( Vigna radiata ) are the main food legumes grown in Cote d ’ Ivoire and the localities of Haut-Sassandra. These legumes are highly valued for their nutritional, agronomic and economic value. Groundnut, cowpea and soybean are the main food legumes grown in Cote d ’ Ivoire and in the localities of Haut-Sassandra. On the other hand, Ivorian soils are characterized by a tendency towards acidification and a decrease in the content of nutrients such as phosphorus and nitrogen which have a direct impact on the products. To restore soil fertility, farmers use mineral fertilization. However, this fertilization has an influence on the nodulation of these legumes. The study took place at Jean Lorougnon University. We adopted a completely random experimental block device. The parameters measured included the number of nodules, the length and weight of the plant, the length and weight of the root system. Our results showed that mineral fertilization reduced the nodulation capacity of legumes. However, a small dose of phosphorus (<2 g) would be required for early growing legumes.

In rotational cropping systems, legume-fixed nitrogen can be used first by the legumes and then by subsequent crops [

Despite their nutritional and agricultural importance, legumes’ yields are still low in our country. This low yield can result from the control of the quality of the sufficient information, the quality of cultural practice and especially the decline in fertility [

· fertilization influences the agronomic parameters of legumes;

· there are fertilizer doses to increase the nodulation of the three legumes alone or in combination.

The study was carried out on an experimental plot in the locality of Daloa. The city of Daloa is located in the Upper Sassandra region of west-central Côte d'Ivoire between 6˚ and 7˚ North latitude and 7˚ and 8˚ West longitude. This region has an area of 15,200 km^{2} for an estimated population of 1,430,960 inhabitants. The department of Daloa is bounded in the North by the departments of Vavoua and Zuénoula, in the South by those of Issia and Sinfra, in the west the county districts of Duékoué and Bangolo and in the East by that of Bouaflé. It covers an area of 5423 km^{2}, comprising 137 localities and 6 sub-prefectures (^{2}.

The plant material used in this study consisted of three legume species from the Jean Lorougnon Guédé University collection. It is between the other Vigna unguiculata, Vigna radiata and Arachis hypogaea (

three species is due to the fact that they are more cultivated and consumed in the Upper Sassandra region.

The experimental device used is that of completely randomized blocks with three repetitions. A plot of 5 m^{2} was divided into 3 blocks distant from each other by 0.5 m. Each block consists of 28 elementary batches spaced 0.05 m apart. Each lot consists of 5 pots. These pots are actually bags of black polyethylene 80 microns thick, 25 cm high and 12 cm wide flat. They are filled with earth 7.5 cm in diameter and 21 cm high, a volume of one liter and a weight of about 1.2 kg. The lots are arranged in 4 rows per block. Each row corresponds to a single dose of nitrogen, phosphorus or nitrogen-phosphorus mixture (0 g, 2 g, 4 g or 6 g) (

All data were collected six weeks after sowing corresponding to the flowering period. They concerned the number of nodules, the length of the plant and that of the root system, the weight of the plant and that of the root system. All measurements were taken on three feet of each lot taken at random for each species. However, care must be taken to avoid the cutting of secondary roots and the loss of nodules detached from the roots by ridding the plants of the bags. The root of the plants is soaked in water to better see and count the nodules measurements began with the counting of nodules which consisted in giving the number of nodules on the root system of the plant. The length of the plant consisted in measuring the distance of the main stem from the neck to the most extreme leaf. That of the root system from the neck to the end of the root. They were measured using a tape measure. The root system was separated from the plant and its weight was determined using a precision Howell scale 5 kg × 1 g. The weight of the plant was also determined.

The data collected for each of the 5 variables were entered with the Excel spreadsheet version 97-2003 and then processed taking into account the species and the fertilizer using the STATISTICA version 7.1 software through analysis of variance (ANOVA). The significance of the test was determined by comparing the probability (P) associated with the threshold statistic α = 0.05. When a significant difference was observed between the characters, the ANOVA was supplemented by the Smallest Significant Difference (LSD) test. SDPP allows you to see homogeneous groups, since it tells us where this significant difference is. This analysis of variance makes it possible to note the significant differences between the species and the mineral fertilizers considered.

The results of the analysis of variance indicate that agronomic parameters were influenced by mineral fertilization. Significant differences were observed in all fertilizer rates applied to groundnut for all agronomic parameters (

Measurements made on the length of the plant showed that groundnuts grown with 2 g of nitrogen recorded the highest average (16.75 ± 21.6), while that cultivated with 4 g of nitrogen had the highest average low average (6.41 ± 5.2). The length of the plant is significantly identical for groundnut grown with 6 g of nitrogen, phosphorus (2 g, 4 g and 6 g), the nitrogen-phosphorus mixture (2

Variables | Averages (±gap-type) | Statistics | ||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|

2 gN | 4 gN | 6 gN | 2 gP | 4 gP | 6 gP | 2 gNP | 4 gNP | 6 gNP | D0 | F | P | |

N. NOD | 16.91 ± 15.0^{a } | 3.33 ± 5.0^{a} | 2.00 ± 6.9^{a} | 5.41 ± 9.1^{a} | 9.41 ± 16.0^{a} | 2.83 ± 4.2^{a} | 4.16 ± 7.1^{a} | 9.50 ± 7.6^{a} | 9.66 ± 20.2^{a} | 59.83 ± 24.2^{b} | 3591.2 | 0.0 |

L. p (cm) | 16.75 ± 21.6^{c} | 6.41 ± 5.2^{a} | 9.25 ± 3.9^{b} | 10.91 ± 3.3^{b} | 10.41 ± 3.8^{b} | 9.75 ± 2.9^{b} | 9.00 ± 2.8^{b} | 8.50 ± 2.4^{b} | 6.66 ± 3.3^{b} | 13.66 ± 5.0^{b} | 1.9 | 0.0 |

P. p (g) | 40.14 ± 29.9^{b } | 18.15 ± 13.6^{a} | 19.26 ± 9.2^{a} | 43.87 ± 27.0^{b} | 46.10 ± 29.5^{b} | 37.33 ± 25.3^{b} | 36.47 ± 18.0^{b} | 29.46 ± 19.6^{a} | 25.93 ± 11.0^{a} | 60.08 ± 32.3^{c} | 3.9 | 0.0 |

L. SR (cm) | 36.08 ± 15.3^{e} | 15.66 ± 12.3^{a} | 22.16 ± 6.4^{b} | 28.00 ± 3.9^{d} | 35.75 ± 8.7^{e} | 32.33 ± 9.4^{d} | 30.50 ± 6.6^{d} | 34.08 ± 7.3^{e} | 27.41 ± 5.8^{c} | 29.50 ± 8.0^{d} | 6.0 | 0.0 |

P. SR (g) | 9.56 ± 8.3^{a} | 6.86 ± 8.2^{a} | 9.66 ± 5.9^{a} | 10.76 ± 7.3^{a} | 8.73 ± 5.4^{a} | 8.73 ± 5.7^{a} | 12.67 ± 6.7^{a} | 9.06 ± 4.9^{a} | 7.81 ± 3.8^{a} | 11.95 ± 6.8^{a} | 0.9 | 0.5 |

For each variable, values with the same letters on the line are statistically equal. 2 gN: two grams of nitrogen, 4 gN: four grams of nitrogen, 6 gN: six grams of nitrogen, 2 gP: two grams of phosphorus, 4 gP: four grams of phosphorus, 6 gP: six grams of phosphorus, 2 gNP: two grams of Nitrogen-phosphorus mixture, 4 gNP: four grams of the nitrogen-phosphorus mixture, 6 gNP: six grams of the nitrogen-phosphorus mixture, D0: zero dose. N.NOD: Number of nodules, L. p. (cm): Length of the plant, P. p. (g): Weight of the plant, L. SR (cm): Length of the root system, P. SR (g): Weight of the root system.

g, 4 g and 6 g) and of that cultivated without the use of mineral fertilizers. As for the weight of the plant, the highest average was obtained in groundnut cultivated without the use of mineral fertilizers (60.08 ± 32.3), while the lowest average was recorded at the level of 4 g. nitrogen (18.15 ± 13.6). Groundnuts grown with 2 g of nitrogen, phosphorus (2 g, 4 g and 6 g) and 2 g of nitrogen-phosphorus are significantly identical. In terms of the length of the root system, peanuts grown with 2 g of nitrogen gave the highest average (36.08 ± 15.3), while the lowest average was obtained in groundnut cultivated with 4 g of nitrogen (15.66 ± 12.3). The length of the root system is significantly identical for groundnuts grown with 2 g of phosphorus, 6 g of phosphorus, 2 g of nitrogen-phosphorus and that grown without the use of mineral fertilizers. The weight of the root system showed no significant difference for peanuts grown with or without mineral fertilizers.

Variables such as number of nodules, plant length, plant weight, length of root system and root system weight in cowpea were measured and analyzed in relation to mineral fertilization. Results from statistical analyze showed a significant difference between the different doses of mineral fertilization (

Variables | Averages (±gap-type) | Statistics | ||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|

2 gN | 4 gN | 6 gN | 2 gP | 4 gP | 6 gP | 2 gNP | 4 gNP | 6 gNP | D0 | F | P | |

N. NOD | 1.41 ± 2.2^{a} | 4.72 ± 12.0^{a} | 0.83 ± 2.8^{a} | 1.58 ± 2.8^{a} | 2.66 ± 6.1^{a} | 1.16 ± 1.9^{a} | 0.00 ± 0.0^{a} | 1.00 ± 2.4^{a} | 1.50 ± 4.3^{a} | 35.91 ± 27.4^{b} | 14.7 | 0.0 |

L. p (cm) | 9.66 ± 4.2^{c} | 13.77 ± 4.5^{f} | 8.14 ± 6.0^{b} | 11.50 ± 3.4^{e} | 16.58 ± 1.5^{g} | 11.00 ± 4.2^{d} | 4.91 ± 3.5^{a} | 10.66 ± 3.9^{d} | 7.38 ± 5.1^{b} | 16.69 ± 3.3^{g} | 10.0 | 0.0 |

P. p (g) | 25.85 ± 19.4^{c} | 38.81 ± 26.1^{e} | 15.68 ± 17.6^{b} | 24.75 ± 16.7^{c} | 47.81 ± 6.1^{f} | 25.11 ± 14.8^{c} | 6.81 ± 5.2^{a} | 17.11 ± 14.7^{b} | 8.88 ± 7.7^{b} | 29.75 ± 21.4^{d} | 7.2 | 0.0 |

L. SR (cm) | 16.88 ± 8.8^{b} | 23.91 ± 11.7^{d} | 15.66 ± 12.5^{b} | 18.50 ± 4.5^{c} | 20.58 ± 5.1^{c} | 18.25 ± 4.0^{c} | 13.33 ± 8.3^{b} | 16.33 ± 6.4^{b} | 11.66 ± 7.6^{a} | 28.75 ± 10.2^{e} | 4.2 | 0.0 |

P. SR (g) | 7.09 ± 6.2^{c} | 11.35 ± 9.2^{e} | 3.96 ± 4.1^{c} | 7.20 ± 6.2^{c} | 9.75 ± 5.0^{d} | 6.93 ± 4.0^{e} | 2.03 ± 1.2^{a} | 5.12 ± 3.6^{c} | 2.56 ± 2.1^{b} | 10.91 ± 8.8^{e} | 4.0 | 0.0 |

For each variable, values with the same letters on the line are statistically equal. 2 gN: two grams of nitrogen, 4 gN: four grams of nitrogen, 6 gN: six grams of nitrogen, 2 gP: two grams of phosphorus, 4 gP: four grams of phosphorus, 6 gP: six grams of phosphorus, 2 gNP: two grams of Nitrogen-phosphorus mixture, 4 gNP: four grams of the nitrogen-phosphorus mixture, 6 gNP: six grams of the nitrogen-phosphorus mixture, D0: zero dose. N. NOD: Number of nodules, L.p. (cm): Length of the plant, P. p. (g): Weight of the plant, L. SR (cm): Length of the root system, P. SR (g): Weight of the root system.

grown with 2 g of nitrogen, 6 g of nitrogen, 2 g of nitrogen-phosphorus, 4 g of nitrogen-phosphorus and that grown with phosphorus (2 g, 4 g and 6 g).

With regard to the weight of the root system, cowpea grown with 2 g of nitrogen was distinguished by its high average (11.35 ± 9.2) while that cultivated with 2 g of nitrogen-phosphorus recorded the lower average (2.03 ± 1.2). The weight of the root system is significantly identical between cowpea grown with 2 g of nitrogen, 6 g of nitrogen, 2 g of phosphorus and 4 g of nitrogen-phosphorus.

The result of the statistical analysis of the data presented in

Variables | Averages (±gap-type) | Statistics | ||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|

2 gN | 4 gN | 6 gN | 2 gP | 4 gP | 6 gP | 2 gNP | 4 gNP | 6 gNP | D0 | F | P | |

N. NOD | 1.66 ± 2.30^{b} | 1.41 ± 3.05^{b} | 0.41 ± 0.79^{b} | 10.75 ± 12.27^{c} | 10.08 ± 13.13^{b} | 1.66 ± 2.60^{b} | 0.16 ± 0.57^{a} | 0.75 ± 2.05^{b} | 0.58 ± 1.16^{b} | 22.08 ± 16.91^{d} | 9.78 | 0.00 |

L. p (cm) | 12.58 ± 7.83^{b} | 14.70 ± 7.21^{c} | 11.12 ± 8.55^{b} | 17.45 ± 5.13^{c} | 20.70 ± 5.66^{d} | 13.58 ± 9.54^{c} | 7.89 ± 6.28^{a} | 10.83 ± 10.63^{a} | 8.88 ± 5.70^{a} | 23.25 ± 4.88^{e} | 5.54 | 0.00 |

P. p (g) | 13.91 ± 12.88^{a} | 11.28 ± 11.54^{a} | 15.05 ± 23.70^{a} | 10.05 ± 8.48^{a} | 13.06 ± 8.10^{a} | 6.28 ± 6.79^{a} | 6.87 ± 12.03^{a} | 4.88 ± 6.99^{a} | 3.42 ± 3.49^{a} | 17.28 ± 15.33^{a} | 1.77 | 0.08 |

L. SR (cm) | 13.58 ± 9.94^{a} | 16.23 ± 10.18^{b} | 13.41 ± 13.74^{a} | 18.66 ± 6.00^{b} | 20.50 ± 4.75^{b} | 12.58 ± 8.47^{a} | 11.43 ± 10.72^{a} | 10.50 ± 11.16^{a} | 14.66 ± 10.28^{a} | 28.16 ± 9.42^{c} | 3.52 | 0.00 |

P. SR (g) | 2.12 ± 1.88^{a} | 2.07 ± 3.01^{a} | 2.90 ± 5.42^{a} | 1.62 ± 1.46^{a} | 1.82 ± 1.41^{a} | 0.99 ± 1.19^{a} | 1.67 ± 3.35^{a} | 0.56 ± 0.80^{a} | 0.61 ± 0.75^{a} | 3.79 ± 3.41^{a} | 1.29 | 0.24 |

For each variable, values with the same letters on the line are statistically equal. 2 gN: two grams of nitrogen, 4 gN: four grams of nitrogen, 6 gN: six grams of nitrogen, 2 gP: two grams of phosphorus, 4 gP: four grams of phosphorus, 6 gP: six grams of phosphorus, 2 gNP: two grams of the nitrogen-phosphorus mixture, 4 gNP: four grams of the nitrogen-phosphorus mixture, 6 gNP: six grams of the nitrogen-phosphorus mixture, DO: Zero dose. N. NOD: Number of modules, L. P. (cm): lenght of the plant, P.p.(g):weight of the plant, L. SR(cm): Lenght of the root of the root system, P. SR (g): weight of the root system.

at soybean grown with 2 g of nitrogen-phosphorus respectively (0.16 ± 0.57 and 7.89 ± 6.28) (

The results obtained in our study showed that nodulation is influenced by mineral fertilization (nitrogen, phosphorus and nitrogen-phosphorus). The number of nodules depends on the type of fertilizer applied. However, our results are in contradiction with those of Yeboah [

The general objective of our study was to promote cultural practices that can improve the nodulation capacity of legumes. In this study, it was shown that mineral fertilization of legumes negatively affects nodulation. Thus, growing legumes without adding mineral fertilizers gave a high number of nodules. However, a dose of less than 2 g of phosphorus at the beginning of growth of legumes is important. Therefore, the development of legume crops with a low dose of phosphorus would be a way to enrich the soil with nutrients in order to benefit the crops that will succeed.

Our thanks go to the authorities of the University Jean Lorougnon GUEDE and the teachers of the laboratory of improvement and plant production for the efforts made in carrying out this work.

The authors declare no conflicts of interest regarding the publication of this paper.

Jacob, K.N., N’guessan, K., Alphonse, A.K., Joël, Y.K., Koutoua, A. and Justin, Y.K. (2019) Influence of Mineral Fertilization on the Capacity of Nodulation of Three Species of Legumes (Groundnut, Cowpea and Soybean). American Journal of Plant Sciences, 10, 2208-2218. https://doi.org/10.4236/ajps.2019.1012156