Effect of soil nitrate on the growth and nodulation of lupins (Lupinus angustifolius and L. albus)

Abstract

The effect of increasing external nitrate (NO-3) concentration on the nodulation of Lupinus albus and L. angustifolius lines was examined in 2 sand culture experiments. In the first experiment 4 lines, 3 L. albus and 1 L. angustifolius, were grown at NO-3 concentrations of 0, 2, 8, 16, and 30 mmol/L for 49 days. Increasing the NOT concentration reduced nodule weight in all varieties to a similar extent. In a second experiment, 18 L. angustifolius lines were grown at NO-3 concentrations of 2 and 8 mmol/L for 49 days. The ratio of nodule weights at the 8 and 2 mmol/L NO-3 treatments varied widely, from 23 to 71%, between the lines. There appears to be potential for selection of L. angustifolius varieties able to maintain N2 fixation at increased levels of soil N.