Crop response to current and previous season applications of phosphorus as affected by crop sequence and tillage

Field studies were conducted over a 4-yr period at two locations in western Manitoba, Canada, to evaluate the effect of phosphorus (P) fertilizer management on crop growth as affected by tillage system through a 2-yr cropping sequence. In the first phase of the cropping sequence, canola (Brassica napus L.), a non-mycorrhizal crop, and spring wheat (Triticum aestivum L.), a mycorrhizal crop, were grown under conventional (CT) and reduced (RT) systems, with 0.11 and 22 kg P ha-1 applied as monoammonium phosphate (MAP). In the second phase of the sequence, flax (Linum usitatissimum L.) was seeded following the spring wheat or canola, with application of 0 or 11 kg P ha -1 as MAP. Phosphorus application increased the early-season biomass, P concentration, and P accumulation of canola and wheat and the seed yield of canola. Tillage system had no consistent effects on growth, P concentration or uptake, or seed yields of canola or wheat, nor were P by tillage system interactions observed. Early-season biomass production and seed yields of flax were relatively unaffected by P fertilization whether applied in the same season as flax or in the previous season, although early-season P concentration and P accumulation were increased when P fertilizer was applied to the flax. Of the factors evaluated in this study, preceding crop had the greatest influence on flax growth with flax establishment, early-season biomass, and P accumulation, and seed yield all being significantly greater when flax was seeded after wheat than after canola.