Seasonal biomass accumulation and nutrient uptake of canola, mustard, and flax on a black chernozem soil in Saskatchewan

Seed yield and nutrient use efficiency are related to biomass accumulation and nutrient uptake in the growing season. Biomass accumulation and nutrient uptake of canola (Brassica napus L. and Brassica rapa L.), mustard (Brassica juncea L.) and flax (Linum usitatissimum L.) and the relationship to days after emergence (DAE) or growing degree days (GDD) were determined during the 1998 and 1999 growing seasons in field experiments at Melfort, Saskatchewan, Canada. In general, biomass accumulation and nutrient uptake increased with time at early growth stages and reached a maximum at late growth stages. Significant R 2 values for both biomass accumulation and nutrient uptake indicated that a cubic polynomial type equation was suitable to represent these parameters as a function of DAE. All oilseed crops maximized biomass at mid way to the end of pod forming stages (74-84 DAE or 750-973 GDD). Maximum biomass accumulation rate occurred at the early to late bud forming stage (42-49 DAE or 390-498 GDD), and it was 146-190 kg ha(-1)d(-1) for canola, 158-182 kg ha(-1)d(-1) for mustard, and 174-189 kg ha(-1)d(-1) for flax. Maximum nutrient uptake occurred during flowering to early ripening (59-82 DAE or 597-945 GDD). Maximum nutrient uptake rate normally occurred at branching to early bud formation (21-42 DAE or 142-399 GDD). There was a close correlation between biomass accumulation and nutrient uptake, and among nutrients, suggesting interrelated absorption. For nitrogen (N), phosphorus (P), potassium (K), sulfur (S), and boron (B), respectively, maximum nutrient uptake rate was 2.3-4.5,0.3-0.5, 2.5-5.7,0.7-1. 1, and 0.005-0.008 kg ha(-1)d(-1) for canola; 2.3-3.9,0.4-0.5,2.6-4.9, 1.2-1.4, and 0.006-0.008 kg ha(-1)d(-1) for mustard; and 3.2-4.0, 0.3-0.4, 2.9-4.1, 0.3-0.5, and 0.004-0.009 kg ha(-1)d(-1) for flax. In general, maximum nutrient uptake rate and amount occurred earlier than maximum biomass accumulation rate and amount, and maximum rates of both nutrient uptake and biomass accumulation occurred earlier than their maximum amounts. The findings suggest that for high seed yields, there should be adequate supply of nutrients for plants, particularly to sustain high nutrient uptake rate at branching to bud forming stage and high biomass accumulation rate at early to late bud forming stage.