Selection of Non-Fixing Control Plants for Use in 15 N Dilution Method of Quantifying Dinitrogen Fixation in Soybean

Abstract

The choice of the most appropriate non-fixing control plants is essential to the accuracy of estimating N2 fixation by 15N isotope dilution. Experiments were conducted in North and Northeast Thailand using non-nodulating soybean isolines, maize, sorghum, barley, upland rice and wheat, to select appropriate controls for estimating N2 fixation in soybean (Glycine max) by the 15N dilution method. Two Japanese non-nodulating soybean lines, To1 -02 adn A62 - 2, were established as the most appropriate control plants for this type of study with Thai soybean sorghum and barley were also appropriate controls. The choice of the most appropriate control plants is not always clear-cut. It is recommended that several control plants be used in each experiment until the subject is further researched.