Interralations between varieties and nutrition in nodulation and symbiosis of soybean (Glycine max (L.) Merril)

Abstract

Three greenhouse experiments with soybeans were carried out following observations in several field experiments that certain varieties always were abundantly nodulated while others nodulated only on certain soils. In the present experiments one easy nodulating variety (Mamouth) was compared with two varieties presenting difficulties in nodulation (L-571 or L-2006). In confirmation of the field experiments, the variety Mamouth, in all three experiments showed higher nodule weight and nitrogen fixation less affected by the different treatments or by factors not controlled in these experiments. This is apparent in one of the experiments by the low coefficient of variability (11,8%) in the analysis of nodule weight for the variety Mamouth compared to a very high coefficient of variability (47,5%) for the variety L-571. Liming stimulated nodulation and nitrogen fixation of the varieties Mamouth and L-2006 while the effect of gypsum was dependent on the level applied and on the variety. For the variety Mamouth 100 ppm of gypsum seemed to be optimal and 200 ppm for the variety L-2006 whereas 400 ppm of gypsum were excessive for both varieties. The varieties also responded differently to nitrogenous fertilizer. Nitrogen fixation and nodulation for the variety Mamouth were reduced less by N applications than were those of the variety L-2006. The regression of total plant nitrogen (log) with nodule weight showed different coefficients for the two varieties (Mamouth and L-2006) at the lowest N level (10 ppm). This was not the case in the pots without nitrogen or at the highest N level (40 ppm). Magnesium stimulated nodulation and nitrogen fixation of the varieties Mamouth and L-571 while potash seemed to have the opposite effect. It is suggested that physiological differences between varieties, related to calcium and nitrogen metabolism might be the cause of hereditary differences in nodulation and nitrogen fixation of soybeans.