Rhizobium inoculation and the supply of molybdenum and lime affect the uptake of macroelements in common bean (P. vulgaris L.) plants

This study was conducted to investigate the effect of Rhizobium inoculation and the supply of Mo and lime on the uptake of macroelements in P. vulgaris. To achieve this aim, experiments were conducted at the glasshouse of the Cape Peninsula University of Technology, Cape Town (i.e. from August 2008 to January 2009) and field experiment at the Agricultural Research Council (ARC) Nietvoorbij site in Stellenbosch, South Africa (i.e. during the summer seasons from October 2008 to March 2009). A randomised complete block design was used in a 3-factorial arrangement with 2 levels of Rhizobium inoculation (with and without rhizobia), 3 levels of Mo (0, 6 and 12 g kg seeds) and 3 levels of lime (0, 2 and 3 t ha) with 4 replications per treatment. The result showed that Rhizobium inoculation significantly (P ≤ 0.05) increased the uptake of P, K, Ca and Mg in the plant parts attributed to increased soil pH. Similarly, Mo significantly (P ≤ 0.05) increased the uptake of P, K, Ca and Mg in all organs of P. vulgaris but decreased the S content in roots. Application of lime significantly increased the uptake of the macroelements in shoots and whole plant only in the glasshouse probably due to differences in soil volumes between the glasshouse and the field conditions. There was significant interaction between Rhizobium × Mo on P, K and S in roots, shoots and pods of P. vulgaris in glasshouse and field experiments; Rhizobium × lime on the amount of S in shoots and whole plant of P. vulgaris grown in the field experiments; Mo × lime on the uptake of P in roots and Ca in pods in glasshouse as well as P in roots in field studies. Regardless of the type of interaction, combining Rhizobium and Mo at 12 g g seeds and/or lime at 3 t ha maximised the uptake of P and K in roots and Ca in pods compared with zero control. These results suggest that Rhizobium inoculation and the supply of Mo and lime can be of great benefit to farmers growing grain legumes such as P. vulgaris in acidic soils ranging from pH 6.1 to 6.2. Furthermore, these inputs have shown to improve the uptake of P, K, Ca and Mg, which are greatly required by the plant for growth, nodulation and N2 fixation.