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University Microfilms International 300 North ZM b Road Ann Arbor. Michigan 48106 USA St John s Road. Tyler's Green High Wycombe. Bucks. England HP10 8HR 77-17,145 TIARKS, Allan Edward, 1945- CAUSES OF INCREASED CORN ROOT ROT INFECTION OF CONTINUOUS CORN ON NO-TILL UOYTVILLE SILTY CLAY LOAM IN NORTHWESTERN OHIO. The Ohio State University, Ph.D., 1977 Agronomy Xerox University Microfilms,Ann Arbor, Michigan 48106 CAUSES OF INCREASED CORN ROOT ROT INFECTION OF CONTINUOUS CORN ON NO-TILL HOYTVILLE SILTY CLAY LOAM IN NORTHWESTERN OHIO DISSERTATION Presented In Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the Graduate School of the Ohio State University by Allan E. Tlarks, B. Sc., M. Sc. ***** The Ohio State University 1977 Reading Committee: D. M. Van Doren en, Co-advisor G. S. Taylor A. F. Schmitthenner ACKNOWLEDGMENTS This seudy was conducted on soils collected from tillage research plots established by Dr. D. M. Van Doren and others. I am grateful for the use of these long term plots, as without this resource, the present study would have been impossible. I also thank Dr. Van Doren and Dr. G. S. Taylor for their guidance throughout the study* I acknowledge the financial support of the Agronomy Department in form of a teaching assistantshlp under Dr. F. L. Himes. I am indebted to Ms. Lou Ann Cooper for typing and proofing the manuscript. Finally, I would like to extend my appreciation to my fellow graduate students for their Interest and ideas which made the work interesting if not fun. (ii) VITA August 16, 1945 Born - Council Bluffs, Iowa 1967 B.Sc. Agronomy, Iowa State University, Ames, Iowa 1967-1969 Peace Corps Volunteer Soil Survey in Tanzania, Africa 1969-1970 Research Assistant, University of Nebraska, Lincoln, Nebraska 1970-1971 U.S. Army 1972-1973 Research Assistant, University of Nebraska, Lincoln, Nebraska 1973 M.Sc., Agronomy, University of Nebraska, Lincoln, Nebraska 1973-1976 Teaching Associate, Department of Agronomy, The Ohio State University, Columbus, Ohio Present Research Soil Scientist, Southern Forest Experiment Station, Pineville, Louisiana PUBLICATIONS "Physical and Chemical Properties of Soil Associated with Heavy Applica­ tions of Kanure from Cattle Feedlots." Soil Science Society of America Proceedings 38:826-830. (iii) FIELDS OF STUDY Soil Science: G. S. Taylor, K. R. Everett, E. 0. McLean, F. L. Himes, R. H. Miller, and L. Wilding Mic roc1ima t o1ogy J. N. Rayner and A. J. Amfield Mineralology R. T. Tettenhorst and E. G. Ehlers Botany C. A. Swanson Agricultural Engineering L. D . Drew Statistics H. 0. Harvey Chemistry Q. Van Winkle and M. H. Klapper Physics J. H. Shaw (lv) TABLE OF CONTENTS ACKNOWLEDGEMENTS ii VITA H i LIST OF TABLES viii LIST OF FIGURES xi INTRODUCTION ! CHAPTER I. REVIEW OF LITERATURE 3 A. Morphology, Host Range, and Pathogenicity of Pythium 4 B. Environment of No-tillage Culture and Effects on C o m Root Pathogens 5 1. Soil Temperature 5 2. Soil Water 7 3. Soil Temperature-Soil Water Interactions 10 4. Soil Strength and Bulk Density 10 5. Soil Structure 13 6 . Crop Rotation 14 7. Residue Addition 15 C. Summary 16 II. METHODS AND MATERIALS 18 A. General Information 18 B. General Laboratory Methods 20 1. Root Growth in Soil Core Techniques 20 2. Com Root Baiting Technique 23 C. Preliminary Investigations 23 1. Effect of Bulk Density on Com Growth 23 2. Effect of Pythium on Com Growth 24 (v) D. Measurement of Inoculum Potential of Pythium 25 1. Soil Mass Variable 25 2. Effect of Variable Concentrations of Fungicides 25 3. Soil Mass vs Area of Soil Exposed 27 4. Infinite Thickness 27 5. Surface Area Varied 28 E. Field Core Experiments 29 1. Autumn Core Experiment 30 2. Bulk Density of Clods 31 3. Spring Core Experiment 31 4. Samples of Com Plants From the Field 32 F. Evaluation of Specific Hypotheses 33 1. Bulk Density by Pythium Interaction 33 2. Effect of Organic Amendments 35 3. Pythium Buildup Along Cracks 39 III. RESULTS AND DISCUSSION 44 A. Preliminary Investigations 44 1. Effect of Bulk Density on Com Growth 44 2. Effect of CRP Infection on Corn Growth 46 3. Discussion of Preliminary Investigations 49 B. Measurement of Inoculum Potential of Pythium in Soil 50 1. Soil Mass Variable 50 2. Effect of Variable Concentrations of Fungicides 50 3. Soil Mass vs Area of Soil Exposed 54 4. Infinite Thickness 54 5. Surface Area Varied 54 6 . Discussion of Inoculum Potential Measurement 60 C. Field Core Experiments 67 1. Autumn Core Experiment 67 2. Bulk Density of Clods 73 3. Spring Core Experiment 73 4. Samples of C o m Plants From the Field 78 5. Discussion of Field Sampling 81 (vi) D« Evaluation of Specific Hypotheses 84 1. Bulk Density by Pythium Interaction 84 2. Effect of Organic Amendments 87 3. Pythium Buildup Along Cracks 98 IV. SUMMARY AND CONCLUSIONS 110 V. APPENDICES 113 VI. LITERATURE CITED 124 (vii) LIST OF TABLES Selected properties of Hoytvllle and Wooster soils. 19 Variables used In the series of experiments to evaluate methods of measuring Inoculum potential of Pythium in soil. 26 Summary of variables used to test the three hypotheses proposed as causing increased infection of c o m roots in no-tillage c o m plots. 34 Regression equations and regression coefficients between bulk density (X) and nine parameters of c o m (Y) . 45 Root weight and root length of c o m plants grown in flasks over Hoytvllle soil from continuous sod and continuous c o m plots. 48 Root lengths of five c o m plants grown above three different amounts of Pythium infested soil. 51 Effect of four concentrations of the fungicide, pyroxychlor, on root growth of c o m plants exposed to Pythium infested soil. 52 Length of c o m root from five plants grown in flasks containing different numbers of vials filled to different depths of soil. Each value is the average of six replications. 55 Root lengths of c o m plants grown in cores of Hoytvllle and Wooster soils that had been subjected to three field and three laboratory treatments. 69 Total phosphorus content of c o m plant tops grown in Hoytvllle and Wooster soil cores. 71 Phosphorus uptake per unit length of root of c o m plants grown in Hoytvllle and Wooster soil cores. 72 Bulk densities of Hoytvllle soil as determined from core and clod samples and of Wooster soil as determined by core samples. The samples were taken in October, 1975. 74 (viii) Root length of c o m plants grown on Hoytvllle soil cores representing four field treatments and subjected to four laboratory treatments. The cores were collected In April, 1976. Each value Is the average of three replications. 76 Phosphorus content of corn tops and uptake per unit of root length from Hoytvllle soil cores representing two field treatments and two laboratory treatments. Each value is the average of 12 determinations. 77 Dry plant weights and total potassium and phosphorus contents of corn plants collected from the field plots at Hoytville 57 days after planting. Each value is the average of nine determinations. 79 Effect of bulk density of Hoytville soil and pyroxychlor fungicide treatment on root length and uptake of potassium and phosphorus per unit length of root. Each value is the average of 12 determinations. 85 Root lengths of c o m plants grown in flasks containing Infested soil, treated with various amounts of c o m stalk residue, or steamed soil incubated for different times. 89 Root lengths of c o m plants grown in Hoytville soil cores treated with and without an organic amendment, pyroxychlor, and ammonium nitrate. Each value is the average of four replications.