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

Grant, C. A., Monreal, M. A., Irvine, R. B., Mohr, R. M., McLaren, D. L. and Khakbazan, M. 2009. Crop response to current and previous season applications of phosphorus as affected by crop sequence and tillage. Can. J. Plant Sci. 89: 49-66. 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.