Soybean growth with respect to N fertilizer rates, plant population densities and two cultivars was investigated on three Quebec soils at four sites. Soybean nodulation, growth, grain yields and nutrient uptake at three developmental stages were investigated. Soil nitrate levels after harvest were also studied. / N fertilizer application depressed soybean nodulation consistently, but improved soybean growth where initial soil nitrate levels were low. Grain yield was increased at one site with added N, where soybean growth was stressed by low initial soil nitrate levels (below 17 kg N/ha) and severe summer drought. Soybean N and K uptake were increased with increased N fertilizer but P uptake was not affected. Residual soil nitrate content in the 0-50 cm depth in the fall of the crop year increased linearly and this effect carried over to the following spring. / Plant population had little effect on individual plant nodulation but increased fresh nodule mass per unit area. Plant biomass, grain yield and nutrient uptake were increased with increased population densities. / The cultivar Apache had better nodulation potential and grain yield potential and was better adapted to intensive management practices with high plant populations than the cultivar Maple-Arrow.

No description available.

The economic feasibility of lupins in a cropping system as a protein supplement for a representative dairy cattle herd in Southwest Quebec (SWQ) to substitute for soybeans was investigated using a single period linear programming (LP) model. At current prices, lupins were not a profitable base case scenario. The gross margin of the dairy farm was $147,918. This resulted in a total soil loss of 3,504 tonnes (t), 50 percent higher than soil tolerance, T (acceptable level of soil loss) of 14 t ha$ sp-1,$ and produced 541 kg of Nitrogen (N). Sale of corn grain (CG) was 442.3 t, constituting about 39 percent of the gross margin but had a negative effect on the soil. The farm purchased 59 t of straw for animal bedding. / When the environmental constraint of soil erosion, 14 t ha$ sp{-1},$ was imposed, the gross margin was estimated to be $131,148 while total N and soil loss were 2,454 kg and 1,708 t, respectively. Lupins were produced on 18.3 ha with this soil loss level constraint. The tradeoff between soil loss and gross margin and lupins was observed. The N fixation constraint reduced the gross margin while it increased soil loss. CG sales were reduced from 442 to 244.5 t but milk production increased by 163 hectolitres (HL). Sensitivity analysis on labour supply and farm size indicated that lupins became an alternative to soybeans when farm size and labour supply were larger and fewer respectively. / Lupins would substitute for soybeans if yield is increased by 5 percent; cost of production is reduced by 10 percent and home grown clean lupin seed is used for 2 or 3 more years or government provides a subsidy of $328 ha$ sp-1.$ This is approximately equal to the CG subsidy.

No description available.