Performance of Non‐Nodulating and Nodulating Soybean Isolines in Mixed Culture with Nodulating Cultivars 1

Nodulating and non‐nodulating soybean isolines were grown in mixed culture with six nodulating soybean cultivars to determine if non‐nodulating plants would benefit from an association with nodulating plants. All seed mixtures were half isoline and half cultivar at planting. Pure cultures of the isolines and cultivars were included in the experiments. At maturity, seed yield, seed size, and protein and o11 concentration were determined for each component of the mixed cultures and for each pure culture. The average performance of the non‐nodulated component of the mixture was 38% greater than the average yield of the non‐nodulated line in pure culture. Likewise, protein concentration and total protein were 13 and 56% greater, respectively, in the non‐nodulated lines that were grown in mixed culture with nodulated cultivars. Considering the amount of available soil N at planting and competition of the cultivars for that N, the additional N accumulated by the non‐nod in mixture may have come from other than soll sources. It is likely that N was lost from the nodulated plants either through the sloughing and decomposition of root and nodular tissue and/or through the direct excretion of nitrogenous compounds from the roots. Evidence that the cultivars differed with respect to the amount of N lost, suggests that the trait could be changed with selection and breeding methods.