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v Field studies were conducted in 2017-2018 near Libau, Manitoba, under organic management v Selected soil properties: § Soil pH, 8.0–8.2; Olsen P, 2–3 mg kg -1 v Experimental design: RCBD with four replications v Treatments: Unamended control, plus three rates of commercial struvite fertilizer: § Wheat and flax studies: 20, 30, 40 kg P ha -1 § Alfalfa-grass forage study: 30, 60, 90 kg P ha -1 v Field operations and management outlined in Table 1 v Statistical analysis: One-way ANOVA using Proc GLIMMIX of SAS; mean separation using Tukey’s test (! = 0.05). Response of Organically Managed Crops to Struvite Fertilizer Background v Available soil phosphorus (P) often becomes depleted in Canadian prairie organic cropping systems. 1 v Struvite (NH 4 MgPO 4 -6H 2 O) recovered from municipal wastewater is gaining attention as a slow-release P fertilizer that helps close the global P cycle and is being considered for use in organic systems. v Crop response to struvite may be poor in high-pH soils due to low solubility. 2 v Struvite has not been tested in organically managed grain or forage crops in Canadian prairie soil and climate conditions. Figure 2. Forage biomass and tissue P concentration of alfalfa-grass in each of four hay cuts in 2017–2018, following addition of differing rates of struvite fertilizer in the spring of 2017. Figure 3. Control (left) and 90 kg P ha -1 (right) treatments at time of “Cut 2” sampling in August 2018, 15 months after struvite application. Control 30 kg P ha -1 60 kg P ha -1 90 kg P ha -1 A B Materials and Methods v Organic grain crops exhibited inconsistent responses to struvite addition in this low-P, high-pH soil. v Struvite was an effective P source for organic alfalfa-grass forage in this low-P, high-pH soil. Conclusions v Struvite addition increased grain yield of organically grown spring wheat (1 of 2 years), but not flax. v Struvite addition increased alfalfa-grass forage biomass and tissue P concentration over two years. Wheat Grain Yield v In 2017, wheat yield did not respond to struvite addition (Fig. 1A) v In 2018, all struvite treatments out-yielded the control (Fig. 1A); wheat yield was greatest where the highest rate of struvite was applied. Flax Grain Yield v Flax yield was not affected by struvite application in either year (Fig. 1B) Alfalfa-Grass Biomass Production v Forage biomass production in struvite treatments was greater than the control at all sampling dates except 2017 Cut 1 (Fig. 2A). v In 2018, forage biomass in the medium and high struvite rate treatments was greater relative to the low struvite rate treatment (Fig. 2A; Fig. 3). Alfalfa-Grass P Concentration v Forage P concentration increased with the high rate of struvite application at 3 out of 4 sampling dates (Fig. 2B). 1 Knight, et al. 2010. Can. J. Soil Sci. 90: 667-678. 2 Degryse et al. 2017. Plant Soil 410: 139-152. Highlights To evaluate the agronomic response of organically managed grain and forage crops to differing rates of struvite fertilizer addition in a low-P, high-pH soil. Next Steps v Repeat wheat and flax experiments in 2019, assessing biomass production, tissue P concentration and yield. v Monitor alfalfa-grass biomass production and tissue P in 2019 to assess the duration of the response to struvite addition. v Additional measurements in all 2018 and 2019 experiments: § Soil P fractions as determined by various P extractions, to determine fate of struvite P in soil § Mycorrhizal colonization of crop roots; relationships among AMF, rate of P addition and soil P fractions v Calculate P use efficiency indices for all experiments. v Investigate the role of differing plant P acquisition mechanisms in struvite P mobilization and uptake. References This study was funded by Ostara Nutrient Recovery Technologies. Ongoing research is funded by the Organic Science Cluster 3 under the AgriScience Program of Agriculture and Agri-Food Canada’s Canadian Agricultural Partnership, with support from Ostara Nutrient Recovery Technologies. Acknowledgements Joanne Thiessen Martens 1 , Kimberley Schneider 1 , Francis Zvomuya 1 and Martin Entz 2 1 Department of Soil Science, University of Manitoba, Winnipeg MB; 2 Department of Plant Science, University of Manitoba, Winnipeg MB Presenting author email: [email protected] 0 0.5 1 1.5 2 2.5 3 2017, Cut 1 2017, Cut 2 2018, Cut 1 2018, Cut 2 g kg -1 Alfalfa-Grass Forage Tissue P Concentration P = 0.004 P = 0.051 P < 0.0001 P = 0.014 b b ab a a a a a c b a a b ab a ab 0 1000 2000 3000 4000 5000 6000 2017, Cut 1 2017, Cut 2 2018, Cut 1 2018, Cut 2 kg ha -1 Alfalfa-Grass Forage Biomass P < 0.0001 P < 0.0001 P = 0.070 P = 0.001 a a a a b a a a c b a a c b a a Figure 1. Grain yield of wheat and flax in separate field trials in 2017 and 2018, following addition of differing rates of struvite fertilizer. 0 1000 2000 3000 4000 5000 2017 2018 kg ha -1 Wheat Grain Yield a a a a b b a c P < 0.0001 P = 0.25 0 500 1000 1500 2000 2500 2017 2018 kg ha -1 Flax Grain Yield a a a a a a a a P = 0.18 P = 0.10 Control 20 kg P ha -1 30 kg P ha -1 40 kg P ha -1 Results Table 1. Field operations and management in wheat, flax and alfalfa-grass studies. Wheat, Flax (2017, 2018) Alfalfa-Grass (2017–2018) Establishment Seeded and struvite applied in mid-May, 2017 & 2018 Struvite applied to established forage stand in mid-May 2017 Struvite application Banded with seed in the seed-row Banded approx. 2.5 cm deep, 15 cm spacing Management Mechanical weed control when required (2017 only) Forage cut for hay in early July and late August and removed from plots Measurements Grain yield, collected with plot combine (wheat; flax 2017) or by hand-harvesting (flax 2018) Above-ground biomass samples collected prior to each hay cut to determine forage productivity and tissue P concentration A B Results, continued Study Objective
