THE EFFECT OF NITROGEN-FERTILIZATION AND POPULATION-DENSITY OF THE FIELD BEAN (VICIA-FABA L. MINOR) OF INDETERMINATE AND DETERMINATE GROWTHHABIT ON THE SYMBIOSIS WITH ROOT-NODULE BACTERIA AND ON THE SEED YIELD

Field beans of indeterminate (cv. Nadwislanski) and determinate (cv. T ibo) growth habits were grown on field plots with a density of 20, 40 and 80 plants m(-2) at two levels of nitrogen fertilization: low (20 k g N ha(-1)) and very high (150 kg N ha(-1)). At the phase of intense p od growth the number and the dry matter weight of root nodules as well as their nitrogenase activity and some features of the plants growth were determined, and in the period of ripeness the components of seed yield were established. It was found that increased density of sowing as well as the high level of nitrogen fertilization inhibited the grow th and development of root nodules and limited their nitrogenase activ ity in both cultivars. Plants of both varieties were characterized by a similar potential of forming the root nodules, however, in plants of the cv. Tibo the nitrogenase activity of nodules was much lower than in the cv. Nadwislanski. Increased population density of the plants ha s in both varieties given increased seed yield when calculated per m(2 ) of the soil, compensating in excess the depression of the seed yield from one plant. Such compensation did not occur in the case of the de pression of nitrogen fixation under intense nitrogen fertilization.