A model of critical phosphorus concentration in the shoot biomass of wheat
Bélanger, G., Ziadi, N., Pageau, D., Grant, C., Högnäsbacka, M., Virkajärvi, P., Hu, Z., Lu, J., Lafond, J., Nyiraneza, J. (2015). A model of critical phosphorus concentration in the shoot biomass of wheat, 107(3), 963-970. http://dx.doi.org/10.2134/agronj14.0451
© 2015 by the American Society of Agronomy, 5585 Guilford Road, Madison, WI 53711. All rights reserved. Critical nutrient concentrations are required for assessing the level of crop nutrition. Our objectives were to validate an existing model of critical phosphorus concentration (P<inf>c</inf> = 0.94 + 0.107N) in the shoot biomass (SB) of wheat (Triticum aestivum L.) and to assess the alternative approach of expressing P<inf>c</inf> as a function of SB rather than shoot N concentration (N). We applied four rates of P fertilizer (0, 10, 20, and 30 kg P ha<sup>–1</sup>) on soils with a low to medium available P concentration at four locations in three countries (Normandin [Canada; 2010, 2011, 2012], Brandon [Canada; 2010, 2012], Ylistaro [Finland; 2010, 2011], and Beijing [China; 2012]) for a total of 8 site-years. Shoot biomass, and N and P concentrations were measured on ‑ ve dates with 1-wk intervals from vegetative to late heading stages of development, and grain yield was measured. Increasing P fertilization did not increase grain yield at any of the 8 site-years and had little e ect on SB. Under nonlimiting P conditions achieved in most cases with no applied P, the allometric relationship between P<inf>c</inf> and SB di ered among locations, while the relationship between P<inf>c</inf> and shoot N concentration (P<inf>c</inf> = -0.677 + 0.221N - 0.00292N2, R2 = 0.82, P < 0.001) was independent of locations. This model of critical P concentration predicts lower P<inf>c</inf> values than that previously reported, mostly for high shoot N concentrations. This predictive model of P<inf>c</inf> can be used to quantify the degree of P de‑ ciency during the wheat growing season.
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