EXAMINING THE GROWTH AND NITROGEN ECONOMY OF ORGANICALLY SELECTED SPRING WHEAT CULTIVARS By Laura Wiebe A Thesis submitted to the Faculty of Graduate Studies of The University of Manitoba in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Department of Plant Science University of Manitoba Winnipeg, Manitoba Copyright © 2014 by Laura Wiebe TABLE OF CONTENTS ABSTRACT ......................................................................................................................................... III ACKNOWLEDGEMENTS ................................................................................................................ IV LIST OF TABLES & FIGURES ........................................................................................................ VI 1. INTRODUCTION .............................................................................................................................. 1 2. LITERATURE REVIEW .................................................................................................................. 6 2.1 ORGANIC AGRICULTURE ................................................................................................................ 6 2.1.1 SOIL FERTILITY............................................................................................................................ 6 2.1.2 Weed Management and Ecology ............................................................................................ 8 2.1.3 Crop Yields in Organic Systems ........................................................................................... 10 2.1.4 Specialized Breeding Programs ........................................................................................... 11 2.2 WHEAT ......................................................................................................................................... 14 2.2.1 Origin and Importance......................................................................................................... 14 2.2.2 Production ........................................................................................................................... 16 2.2.3 Wheat Growth and Yield ...................................................................................................... 17 2.3 NITROGEN .................................................................................................................................... 23 2.3.1 Overview .............................................................................................................................. 23 2.3.2 Soil-Plant N cycling ............................................................................................................. 23 2.3.3 Nitrogen Uptake and Partitioning ....................................................................................... 25 2.3.4 Nitrogen and Yield ............................................................................................................... 26 2.3.5 Nitrogen and Grain Quality ................................................................................................. 28 2.3.6 Nitrogen Use Efficiency ....................................................................................................... 30 3. MATERIALS AND METHODS ..................................................................................................... 37 3.1 SITE DESCRIPTION ........................................................................................................................ 37 3.2 EXPERIMENTAL DESIGN AND TREATMENTS.................................................................................. 39 3.3 FIELD TRIAL MANAGEMENT ......................................................................................................... 40 3.4 DATA COLLECTION ....................................................................................................................... 41 3.5 DATA ANALYSIS ........................................................................................................................... 45 4. RESULTS AND DISCUSSION ....................................................................................................... 43 4.1 AGRONOMIC PERFORMANCE ........................................................................................................ 43 4.1.1 Emergence and Stand Density ............................................................................................. 43 4.1.2 Biomass Production ............................................................................................................. 44 4.1.3 Harvest Index ....................................................................................................................... 47 4.1.4 Mid-Season Harvest Index ................................................................................................... 49 4.1.5 Kernel Density ..................................................................................................................... 51 4.1.6 Kernel Weight ...................................................................................................................... 52 4.1.7 Kernel Number per unit of Dry Matter at Anthesis .............................................................. 55 4.1.8 Height ................................................................................................................................... 56 4.1.9 Weed competition ................................................................................................................. 58 4.1.10 Disease Pressure ................................................................................................................ 60 4.1.11 Yield ................................................................................................................................... 62 4.2 NITROGEN DYNAMICS .................................................................................................................. 68 4.2.1 Soil Nitrogen ........................................................................................................................ 68 4.2.3 Grain Protein ....................................................................................................................... 74 4.2.4 Nitrogen yield per unit of N accumulated at Anthesis .......................................................... 76 4.2.5 Nitrogen Harvest Index ........................................................................................................ 77 4.2.6 Grain Nitrogen Yield ............................................................................................................ 80 5. CONCLUSIONS ............................................................................................................................... 83 6. GENERAL DISCUSION ................................................................................................................. 86 7. LITERATURE CITED .................................................................................................................... 96 8. APPENDIX A ................................................................................................................................. 110 9. APPENDIX B .................................................................................................................................. 119 ii ABSTRACT Wiebe, Laura A., The University of Manitoba, 2014. Examining The Growth and Nitrogen Economy of Organically Selected Spring Wheat Cultivars. Major Professor; Martin H. Entz. The nitrogen uptake of organically selected and conventional spring wheat cultivars was assessed throughout the growing season. High protein yielding advanced lines (F8) were selected from the Agriculture and Agri-Food Canada and the University of Manitoba’s joint organic breeding program. Fourteen lines were examined in 2009 and eleven were examined in 2010. An additional organically selected line BW881 from the University of Saskatchewan’s organic breeding program was included in 2009. The organic breeding lines were compared with check cultivars (‘5602 HR’, ‘Kane’, ‘McKenzie’, ‘Cadillac’ in 2009 and 2010, and ‘AC Barrie’ in 2009 only). Combined analysis of the four study site years found significant differences between the organic and check cultivars. The organic lines were found to have higher average yield, grain N yield, kernel density, HI, and NHI while the check cultivars were found to have higher average grain protein. No significant differences were observed between organic lines and the check cultivars for biomass and N biomass accumulation. The strong performance of the organic breeding lines compared to their conventional counterparts for several key parameters is a positive indication of the benefits of specialized breeding programs. The organic lines were more efficient at transferring accumulated biomass into the final grain product. The higher organic grain N yields also indicated that the organic lines were more efficient at transferring accumulated N into the grain. The higher yield of the organically selected lines indicates that they were better able to cope with the environmental stresses associated with organic growing conditions. The organically selected lines did not extract significantly higher amounts of soil N than the check cultivars but were more efficient at remobilizing accumulated N into the final grain product than the conventionally selected checks. iii ACKNOWLEDGEMENTS It is difficult