Abstract

Plants and soil microorganisms have responsive mechanisms to obtain, mineralize and recycle soil phosphorus (P) to preserve cell homeostasis under P starvation conditions. Of the total soil P, organic P (Po) is the most abundant fraction, and phytic acid is the most abundant Po compound. Accordingly, Po is mineralized into soil solutions by phosphatases and phytase, respectively. Otherwise, is little is know about the dynamic of phosphatase and phytase activity of soil in each phenological stages of crops. A greenhouse study was conducted to examine weekly the acid phosphatase and phytase activities in the rhizosphere of soil-canola (Brassica napus) and soil-wheat (Triticum aestivum) from seeding to maturity. For each crop, four replicated treatments were established: soil alone; soil + crop (unfertilized); soil + crop + fertilizer-N; soil + crop + fertilizer-NP. The soil belonged to a Manotick series of the Haplorthods (Melanic Brunisol) Great Group. Overall, soil acid phosphatase activity was higher in wheat than in canola rhizosphere,and in planted versus unplanted soil. In both crop rhizospheres, the highest phosphatase activity occurredin the N+P treatment, and the lowest activity occurred in the soil alone and the unfertilized crops. In canola, phosphatase activity in the N+P treatment was highest 35 days after seeding (DAS; 7 leaves), and after 42 DAS in wheat(6 to 7 tillers, end of heading). The lowest activities were measured after 7 and 56 DAS in canola, and at 14 DAS and beyond 49 DAS in wheat. In canola rhizosphere, soil phytase activity was highest under the N+P treatment 56 DAS, and lowest in the soil alone and the unfertilized crop 7 DAS. This poster will also present and discuss phytase activities in wheat rhizosphere.