Effect of Soil Types and Mixtures on Nodulation of Some Beans and Groundnut Varieties

Groundnuts and beans have long been recognized as good sources of proteins and essential amino acids. Groundnut on its part is a good source of vegetable oil. The types of soil, rhizobia and nutrient components of the soil have long been known to affect the productivity and growth of nodule-forming legumes. This information was the basis of a field study carried out at the Yaba College of Technology botanical garden to determine nodule formation by soil types and their mixtures in five (5) beans and two (2) ground cultivars. Nodules were formed by all the beans and groundnut varieties in loamy soil. Beans variety 3 (brown/white beans) formed 19 nodules, while groundnut, Arachis hypogea ALR2 26 nodules. All beans varieties nodulated in humus soil, but less number of nodules were formed compared with loamy soil. Of the two groundnut varieties investigated, only Arachis hypogea ALR2 nodulated in humus soil. Beans 5 alone (brown/molted beans) nodulated in sandy soil. Groundnut ALR2 formed nodules in all the soil mixtures (except humus/loamy) than any of the beans varieties with mean nodules as high as twenty-eight (28) in clay/loamy soil. Analysis of the results using SPSS Version 17 showed that number of nodules and diameter of each plant stem are not significant at 5% confidence level (P < 0.005), while size of nodule formed is significant. In addition, there is significant positive association for nodule size and nodules numbers for clay soil at 5% confidence level (P < 0.005), whereas there is significant negative association for nodules size and numbers for clay and humus mixtures at 5% confidence level (P < 0.005). Using independent t-test for difference in means between nodules number and size, it was found that only sand/clay mixture and clay/humus are significant at 5% (P < 0.005) confidence level, while other soil types and their mixtures were not significant at the same level of confidence. This means there is no significant difference between the means of the number of nodules and nodule size. From the statistical analysis, clay and sandy soils were poor in encouraging nodule formation as they have the highest mean differences.