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Graduate Theses and Dissertations Iowa State University Capstones, Theses and Dissertations

2015 Plant tissue analysis to assess phosphorus and potassium nutritional status of corn and soybean in Iowa Andrew John Stammer Iowa State University Follow this and additional works at: https://lib.

dr.iastate.edu/etd Part of the Agricultural Science Commons, Agriculture Commons, Agronomy and Crop Sciences Commons, and the Soil Science Commons This Thesis 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 Graduate Theses and Dissertations by an authorized administrator of Iowa State University Digital Repository. For more information, please contact digirep@iastate.edu. Recommended Citation Stammer, Andrew John, Plant tissue analysis to assess phosphorus and potassium nutritional status of corn and soybean in Iowa (2015). Graduate Theses and Dissertations. 14709. https://lib.dr.iastate.edu/etd/14709 Plant tissue analysis to assess phosphorus and potassium nutritional status of corn and soybean in Iowa by Andrew John Stammer A thesis submitted to the graduate faculty in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Major: Soil Science (Soil Fertility) Program of Study Committee: Antonio P. Mallarino, Major Professor John E. Sawyer Allen D. Knapp Iowa State University Ames, Iowa

2015 Copyright ? Andrew John Stammer, 2015. All rights reserved. ii TABLE OF CONTENTS LIST OF TABLES iii LIST OF FIGURES iv CHAPTER 1. GENERAL INTRODUCTION

1 CHAPTER 2. PLANT TISSUE ANALYSIS: PHOSPHORUS AND POTASSIUM FOR CORN AND SOYBEAN IN IOWA

3 ABSTRACT

3 INTRODUCTION

4 MATERIALS AND METHODS

8 Sites, Soils, and Trials

8 Plant Measurements

13 Data Management and Statistical Analyses

14 RESULTS

15 Relationships between Grain Yield Response and Tissue Phosphorus Concentration

17 Relationships between Grain Yield Response and Tissue Potassium Concentration

20 Conclusions

24 REFERENCES

25 CHAPTER 3. GENERAL CONCLUSIONS

42 iii LIST OF TABLES Table 1. Location, tillage system, soils, and soil properties at each P site.

32 Table 2. Location, tillage system, soils, and soil properties at each K site.

33 Table 3. Models fit to relationships between grain yield and tissue P concentrations for corn and soybean.

35 Table 4. Models fit to relationships between grain yield and tissue K concentrations for corn and soybean.

35 iv LIST OF FIGURES Figure 1. Relationships between P concentrations in plants at the V5-V6 growth stage and in leaves at early reproductive growth stages for corn and soybean.

36 Figure 2. Relationships between K concentrations in plants at the V5-V6 growth stage and in leaves at early reproductive growth stages for corn and soybean.

37 Figure 3. Relationship between corn relative grain yield and the P concentration of plants at the V5-V6 growth stage or ear-leaves at the R1 stage. QP, quadratic plateau;

LP, linear plateau;

critical concentrations are shown.

38 Figure 4. Relationship between soybean relative grain yield and the P concentration of plants at the V5-V6 growth stage or uppermost mature leaves at the R2-R3 stage. QP, quadratic plateau;

LP, linear plateau;

critical concentrations are shown.

39 Figure 5. Relationship between corn relative grain yield and the K concentration of plants at the V5-V6 growth stage or ear-leaves at the R1 stage. QP, quadratic plateau;

LP, linear plateau;

critical concentrations.