COMPARISON OF PARAMETERS OF SOIL PHOSPHATE AVAILABILITY FOR THE NORTHWESTERN CANADIAN PRAIRIE

• Published in: Canadian Journal of Soil Science
• Main Author: SOON, Y. K.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 1990
• Subjects: Peace River
• Online Access: http://dx.doi.org/10.4141/cjss90-024; http://www.nrcresearchpress.com/doi/pdf/10.4141/cjss90-024

A greenhouse experiment was conducted to evaluate several P availability parameters using 17 soils from the Peace River region of northwestern Canada. Only one soil was calcareous; the rest were acidic. The extractants tested included alkaline bicarbonate, acidic fluoride and 0.01 M CaCl 2 solutions, and an anion exchange resin. Other availability indices evaluated were phosphoric acid potentials, phosphate buffer capacity and single point P sorption indices. The phosphoric acid potentials gave the highest correlation with percent relative yield of barley dry matter obtained after about 7 wk of growth. P sorption indices were not correlated with any crop response index. The phosphate buffer capacity and resin-extractable P performed at least as well as three chemical extractants: Olsen, Kelowna and Miller-Axley (modified) extractants. These three extractions were further evaluated using yield data from 11 field experiments with barley and 10 with rapeseed. There was little to choose from between these three extractants; however, the Kelowna extractant is a multi-element extractant and more convenient to use than the Olsen method. The Kelowna extractant also has a better buffering capacity, thus giving it a slight advantage over the modified Miller-Axley method for calcareous soils. These soil tests are, however, not fully satisfactory. In the greenhouse study, the Kelowna and Olsen methods made two errors and the modified Miller-Axley method three errors in prediction of P fertilizer requirement or non-requirement for the experimental soils. Key words: Soil testing, phosphate potential, chemical extractants, P sorption index, critical level