Iowa State University Capstones, Theses and Retrospective Theses and Dissertations Dissertations 1985 Hydrolysis and availability to plants of polyphosphates added to soils Richard Peter Dick Iowa State University Follow this and additional works at: https://lib.dr.iastate.edu/rtd Part of the Agricultural Science Commons, Agriculture Commons, and the Agronomy and Crop Sciences Commons Recommended Citation Dick, Richard Peter, "Hydrolysis and availability to plants of polyphosphates added to soils " (1985). Retrospective Theses and Dissertations. 12054. https://lib.dr.iastate.edu/rtd/12054 This Dissertation is brought to you for free and open access by the Iowa State University Capstones, Theses and Dissertations at Iowa State University Digital Repository. It has been accepted for inclusion in Retrospective Theses and Dissertations by an authorized administrator of Iowa State University Digital Repository. For more information, please contact [email protected]. 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Uni International 300 N. Zeeb Road Ann Arbor, Ml 48106 8524644 Dick, Richard Peter HYDROLYSIS AND AVAILABILITY TO PLANTS OF POLYPHOSPHATES ADDED TO SOILS Iowa State University PH.D. 1985 University Microfilms IntGrnâtiOnSl 300 N. zeeb Road, Ann Arbor, Ml 48106 PLEASE NOTE: In all cases this material has been filmed in the best possible way from the available copy. Problems encountered with this document have been identified here with a check mark V . 1. Glossy photographs or pages 2. Colored illustrations, paper or print 3. Photographs with dark background 4. Illustrations are poor copy 5. Pages with black marks, not original copy 6. Print shows through as there is text on both sides of page 7. Indistinct, broken or small print on several pages 8. Print exceeds margin requirements 9. Tightly bound copy with print lost in spine 10. Computer printout pages with indistinct print 11. Page(s) lacking when material received, and not available from school or author. 12. Page(s) seem to be missing in numbering only as text follows. 13. Two pages numbered . Text follows. 14. Curling and wrinkled pages 15. Dissertation contains pages with print at a slant, filmed as received 16. Other University Microfilms International Hydrolysis and availability to plants of polyphosphates added to soils by Richard Peter Dick A Dissertation Submitted to the Graduate Faculty in Partial Fulfillment of the Requirements for the Degree of DOCTOR OF PHILOSOPHY Department; Agronomy Major: Soil Fertility Approved: Signature was redacted for privacy. In Charge of Major Work Signature was redacted for privacy. ^r the Major Department Signature was redacted for privacy. For the Graduate College lova State University Ames, Iowa 1985 ii TABLE OF CONTENTS Page INTRODUCTION 1 LITERATURE REVIEW 5 Characteristics of Polyphosphates 7 Phosphatase Activity of Plant Roots 12 Phosphatase Activity in Soils 24 Polyphosphates as Fertilizers 30 PART I. HYDROLYSIS OF POLYPHOSPHATES BY 34 CORN ROOTS INTRODUCTION 35 MATERIALS AND METHODS 37 Reagents 37 Seed Germination 37 Root Homogenate Studies 39 RESULTS AND DISCUSSION 42 Optimum pH 42 Effect of Temperature 45 Sterile and Nonsterile Root Hydrolysis 50 Effect of Substrates on Induction of 54 Pyrophosphatase PART III. HYDROLYSIS OF POLYPHOSPHATES IN SOILS 58 INTRODUCTION 59 MATERIALS AND METHODS 51 RESULTS AND DISCUSSION 67 iii Effect of air Drying 57 Effect of Incubation Time 69 Effect of Temperature 73 Rate Constants 80 PART III. FACTORS AFFECTING HYDROLYSIS OF 86 POLYPHOSPHATES ADDED TO SOILS INTRODUCTION 87 MATERIALS AND METHODS 89 RESULTS AND DISCUSSION 95 Simple Regression Analyses 96 Multiple Regression Models 107 PART IV. POLYPHOSPHATES AS SOURCES OF 116 PHOSPHORUS FOR PLANTS INTRODUCTION 117 MATERIALS AND METHODS 119 Greenhouse Experiments 122 Plant Analysis 125 RESULTS AND DISCUSSION 127 Yield of Dry Matter 127 Plant P Uptake 140 Extractable P 148 SUMMARY AND CONCLUSIONS 154 LITERATURE CITED 160 ACKNOWLEDGMENTS 172 APPENDIX 173 1 INTRODUCTION Phosphorus (P) is an essential element for plant growth and is important in energy transfer in all living organisms. All soils contain P, but the amounts present and availability to plants vary widely among soils. Phosphorus is present in soils as inorganic compounds, which have very low solubilities, and as organic compounds that contain esters of phosphoric acid, which is slowly mineralized by enzyme-mediated reactions. To correct for the low plant availability of P in soils, man has applied various P-containing materials to soils. Since the 19th century, the use of P fertilizers has increased dra­ matically with the advent of ordinary superphosphoric acid, which is produced by reacting rock phosphate with sulfuric acid. However, when P is added to soils, a large portion of the P is rendered unavailable to plants due to fixation or sorption reactions with soil constituents, which results in only 10-30% of the P added to soils being recovered by plants. To overcome this P fixation problem, alternatives to the conventional P fertilizer (orthophosphate compounds) have been tested. Some organic P compounds added to calcareous soils have shown greater soil infiltration than orthophosphate com­ pounds. Specific condensed inorganic phosphates (polyphos­ phates) have characteristics that could be useful in improving P fertilizer use efficiency. Trimetaphosphate, a cyclic poly­ phosphate, is unigue among polyphosphates in that it remains 2 soluble in the presence of metal ions, such as Ca^"*", 2+ and Ba , and is not sorbed by soil constituents. Linear oligomers added to soils may have residual effects by slowly releasing orthophosphate over the growing season. The key to the availability of polyphosphate-? is the rate of hydrolysis which is mediated chemically and biochemically by a group of enzymes known as phosphatases. Because plants largely take up P in the orthophosphate form, compounds such as polyphosphate must first undergo a hydrolysis reaction in order to release orthophosphate for absorption by plant roots. However, the degradation of polyphosphates should not proceed too rapidly, otherwise, the favorable characteristics of poly­ phosphates would be quickly lost, thus diminishing their po­ tential for increasing P efficiency. With the exception of pyrophosphate, little information is available about hydroly­ sis of polyphosphates in plant root-soil systems. Plant roots have the ability to hydrolyze certain P com­ pounds. This is an important feature because roots that could hydrolyze a polyphosphate would not have to rely solely on hydrolysis reactions in soils in order to make polyphosphate- P available for plant uptake. To distinguish between the role of roots and rhizoplane microorganisms, the hydrolysis rates of a polyphosphate in the presence of sterile and nonsterile intact roots can be compared. The hydrolysis of P compounds added to soils is intimately 3 associated with the mineralization of organic matter in soils as a whole. However, using current methods, the hydrolysis of P compounds added to soils can be studied. Furthermore, the relative contribution of biochemical reactions (phosphatases) and chemical reactions (e.g., metal ion-mediated reactions) towards the hydrolysis of P compounds in soils can be deter­ mined. Hydrolysis reactions are temperature dependent; studies have shown that hydrolysis of pyrophosphate is inhibited in soils under cool temperatures. Thus, temperature is an impor­ tant factor to consider in determining the availability of polyphosphate-P for plants during cool growing periods. The degradation of polyphosphates added to soils is the result of