Effects of Watering Regime and Rhizobium Inoculation on the Growth, Functional and Yield Traits of Four Legume Species

The effects of watering regime and rhizobial inoculation on the growth, nodulation and seed yields of some legume species was evaluated in the screenhouse of the Department of Crop, Soil & Pest Management, Federal University of Technology, Akure, Nigeria. The experimental layout was 5 x 3 x 2 factorial with 3 replications given a total of 90 treatments. Seeds of five staple and forage legume species: Pakala (Phaseolus lunatus), Soy bean (TGX 199057f’ and TGX198057), Stylozanthes (Stylozanthes macrocephala) and the Greenleaf Desmodium (Desmodium intortum (Mill.) Urb.) were sown into plastic pots which were watered at 4-, 8- and 12- days intervals, with or without rhizobium inoculation using a rhizobium strain, Rhizobium phaseoli. The plastic pots (5 litre capacity were perforated at bottom to allow for drainage and were filled with pure river sand. The effect of watering regimes on legume species was significant on leaf development, soybean variety, TGX199057f had the highest number of leaves while Desmodium had the least number of leaves. Seedlings that were watered at 4- and 8-days interval had better vigour of growth compared to 12- days watering interval. Compared with 12-days watering interval, both inoculated and non-inoculated seedlings subjected to 4- and 8-days watering intervals had higher root and shoot biomass. TGX 199057f non- inoculated at 8-days watering intervals had the highest value for number of pods and TGX198057 watered at 12- day intervals had higher pod weight. Rhizobium inoculated legumes produced more vigorous plants in addition to higher root nodules, plant height and number of leaves compared with the non-inoculated species. The highest number of leaves and nodules were produced by Phaseolus lunatus when inoculated with the rhizobium strain. However, the highest number of pods was obtained for inoculated soybean (TGX 199057f) compared with the non-inoculated plants. The highest seed yield was obtained from rhizobium inoculated soybean (TGX 198057). Desmodium produced few seeds compared to Phaseolus lunatus and Styolzanthes. The effects of watering regimes and rhizobium inoculation varied on leaf proximate and chemical composition of legume species. The nitrogen, crude protein, ash, chlorophyll, soluble carbohydrates content in leaf differed among the legume species. The legume species inoculated and grown at 4- days watering intervals had the highest contents of moisture, nitrogen, chlorophyll, soluble carbohydrates and ash compared to non-inoculated legume species. Application of rhizobium strain significantly increased seed yield in soybean and Desmodium and caused substantial increase in nodulation. The study has shown that to increase legume productivity under soil moisture deficit stress of marginal/degraded soil, application of rhizobium inoculant is recommended.