Introduction

1. Responses of Wheat Genotypes to Phosphorus In Organic and Conventional Cropping Systems In the Pacific Northwest Julia L. Piaskowski, Washington State University, Pullman, WA, Chris Hoagland, Purdue University, West Lafayette, IN and Kimberly Garland Campbell, Wheat Genetics, Quality, Physiology and Disease Research Unit, USDA Agricultural Research Service, Pullman, WA Results Introduction Figure 4: Boxplots of Changes in Seed Cu In 2009 Organic Field Site Due to P Fertilizer Table 1: Heat Map of Statistical Significance at a = 0.10* Phosphorus (P) is arguably the most limiting macronutrient in the world. Dwindling resources of easily mineable P, along with water quality concerns and recent spikes in fertilizer prices, have lead to a renewed interest in improving phosphorus use efficiency in crops.  Cu (mg/g seed) Cu (mg/hectare) p=0.0018 nonsignificant Blanca Grande Otis Alpowa Louise Walworth Blanca Grande Louise Walworth Alpowa Otis Figure 5: Boxplots of Changes in Seed Fe Due to P Fertilizer Conventional 2010 (Lind) Organic 2009 (Benge) Data from the ERS p=0.0550 p=0.0217 Materials and Methods p=0.0037 Otis • Field trials were conducted in organic and conventionally-managed locations across Washington state dryland production region in 2009 and 2010 to test the responsiveness of five spring wheat (Triticum aestivum) cultivars to phosphorus fertilizer and inoculation with arbuscular mycorrhizal (AM) fungi. • Each site consisted of two fertilizer treatments, two inoculation treatments, and five cultivars arranged in split-split plot design with four blocks. • The fertilizer treatment consisted of no additional fertilizer and 20 pounds per acre of P2O5, applied as either inorganic ammonium polyphosphate (11-37-0) or OMRI-certified fertilizers from Perfect Blend® and Nature Safe® p<0.0001 p=0.0732 Blanca Grande Blanca Grande Otis *The effect of cultivar is significant for all traits and sites at a = 0.01; those results are omitted because cultivar differences alone are not the objectives of this study. ** All sites except organic 2010 (Boyd) had significant differences for this test. *** All sites except conventional 2010 (Lind) had significant differences for this test Louise Walworth Alpowa Louise Walworth Alpowa Figure 3: Changes in Yield by Phosphorus Fertilizer Mycorrhizal fungal arbuscle infecting Alpowa **Louise: p = 0.0015 **Louise: p = 0.0647 p = 0.0537 Boyd: 2010 Organic Lind: 2009/10 conventional Conclusions Benge: 2009 Organic **Blanca Grande 0.0003 • The statistically significant P-values are broadly spread over multiple variables, main effects and interactions. No obvious pattern is evident across years, sites or management regimes. • The observed response to phosphorus is cultivar-specific and in some cases, site-specific. • The locally adapted cultivar Louise consistently yielded higher than the others and responded to additional P fertilizer despite high soil test P levels during 2010 (12-24 ppm, bicarbonate assay) • Blanca Grande, a hard white wheat from California, performed erratically, undergoing a yield loss under additional fertilizer in the organic field sites. • Differences in seed Cu concentration were cultivar specific for Benge, 2009, but those differences became biologically and statistically insignificant once adjusted for yield per unit area. • Differences in seed concentration of Fe were also cultivar and site-specific. Additionally, those effects are not correlated with Cu or other micronutrients within the same site. • P fertilizer resulted in an increase in P content in early growth tissue, a growth stage in which tissue analysis for P have been shown to identify P deficiencies. These effects were amplified by AM fungi, resulting in increased [P] in the high P samples and decreased [P] in the low samples, possibly due to increased biomass from growth stimulation. **Louise: p = 0.0205 **Louise: p = 0.0806 **Alpowa: p 0.0058 **Otis: p 0.0022 **Blanca Grande 0.0433 Figure 2: Location of Field Sites and Experimental Design **Blanca Grande 0.0180 Map: Spatial Climate Analysis Service Oregon State University Experiment at the Boyd Farm, 2010, (Certified Organic Land) Acknowledgements • Funding was provided by the USDA-OREI Grant (Accession #0218862) and a Washington State University BioAg Seed Grant • Land and consultation provided by the WSU Lind Dryland Experimental Research Station, Gregg Beckley of G&L Farms and by Pat and and Les Boyd All Photos: Julia Piaskowski