SOYBEAN NODULATION AND GRAIN-YIELD AS INFLUENCED BY N-FERTILIZER RATE, PLANT-POPULATION DENSITY AND CULTIVAR IN SOUTHERN QUEBEC

Optimum soybean (Glycine max (L) Merr.) production requires information on the interaction between cultivars, population densities and fertilizer nutrients as related to climate and region. Consequently, field experiments were conducted to determine the effects of N-fertilizer rate, plant population and cultivar on soybean nodulation and grain yield on two soils in southern Quebec. N-fertilizer application consistently depressed soybean nodulation, but it improved soybean growth where initial soil inorganic-N levels were low. High plant population densities had little effect on individual plant nodulation, but they increased fresh nodule mass per unit area. Grain yields were increased with high plant population densities. The two cultivars tested, Apache and Maple Arrow, generally produced similar grain yields on the Ste. Rosalie soil, where yields were low due to moisture stress or tow initial inorganic-N levels. On the more productive Ormstown soil, Apache produced higher grain yields than Maple Arrow.