Improving Potassium Recommendations for Agricultural Crops

Foreword
Acknowledgments
Contents
Editors and Contributors
Abbreviations
Chapter 1: The Potassium Cycle and Its Relationship to Recommendation Development
1.1 Overview of the Potassium Cycle
1.2 Philosophy of a Potassium Recommendation
1.3 Challenges with Common Potassium Recommendation Terminology
1.4 Considerations for Recommendations Derived from the Mass Balance Approach to the Potassium Cycle
1.4.1 Exploring and Characterizing KPlant: Understood and Easily Assessed?
1.4.2 Exploring and Characterizing KSoil: Was Bray Right?
1.4.3 Exploring and Characterizing KFert and EFert: Important but Generally Overlooked?
1.4.4 Potassium Recommendations Without Soil Tests
1.4.4.1 Recommendations Based on Nutrient Removal
1.4.4.2 Recommendations Based on Plant Nutrient Uptake and Yield
1.5 Diagnostics Development: The Undelivered Promise of ``Big Data´´
1.5.1 Data Limitations: Historic and Current
1.6 Opportunities Moving Forward
1.6.1 Mechanistic Modeling
1.6.2 Knowledge Gaps
1.6.3 Tools and Strategies, Data, and e-Infrastructure
1.6.3.1 Underutilized Data Sources with Potential
1.6.3.2 FAIR Data
1.6.3.3 Repositories and Data Publications, Catalogues, Registries, Knowledgebases
References
Chapter 2: Inputs: Potassium Sources for Agricultural Systems
2.1 Overview of Potassium Inputs
2.2 Atmospheric Deposition
2.3 Irrigation Water
2.4 Runoff and Erosion
2.5 Seeds, Cuttings, Transplants, and Residues
2.6 Organic Fertilizer
2.7 Commercial Fertilizer
2.7.1 Resources and Reserves
2.7.2 Materials and Use
2.7.2.1 Potassium Chloride (MOP)
2.7.2.2 Potassium Sulfate (SOP)
2.7.2.3 Potassium Nitrate (NOP)
2.7.2.4 Potassium Thiosulfate (KTS)
2.7.2.5 Langbeinite (SOPM)
2.7.2.6 Polyhalite
2.7.2.7 Potassium Hydroxide (KOH)
2.7.2.8 Potassium Phosphate
2.7.2.9 Mineral/Silicate K
2.7.2.10 Other Potassium Sources
2.7.3 Forms of Potassium Fertilizer
2.7.3.1 Bulk Blends
2.7.3.2 Complex (Compound) Granules
2.7.3.3 Fluid Fertilizers
2.7.4 Potassium for Fertigation
2.7.5 Salt Index
2.7.6 Chloride Considerations
2.7.7 Foliar Potassium Nutrition
2.8 Summary
References
Chapter 3: Outputs: Potassium Losses from Agricultural Systems
3.1 Removal in Harvested Crops
3.1.1 Whole-Plant Removal
3.2 Erosion
3.2.1 Water Erosion
3.2.2 Wind Erosion
3.3 Leaching
3.4 Modeling Potassium Losses
3.4.1 Conceptual Model of Leaching
3.4.2 EPIC
3.4.3 KLEACH
3.4.4 NUTMON
3.4.5 SVMLEACH-NK POTATO
3.4.6 SWAT-K
3.5 Open Burning
3.6 Considerations for Potassium Recommendations
3.7 Conclusions
References
Chapter 4: Rhizosphere Processes and Root Traits Determining the Acquisition of Soil Potassium
4.1 Soil Properties and Processes Determining the Acquisition of Potassium by Plants
4.1.1 Potassium Mobility: Mass Flow Versus Diffusion in the Rhizosphere
4.1.2 Potassium Availability and Bioavailability: Exchangeable Versus Nonexchangeable Pools in the Rhizosphere
4.1.3 Soil Profile Distribution: Topsoil Versus Subsoil Potassium Availability and Bioavailability
4.2 Root Morphological Traits Determining the Acquisition of Potassium by Plants
4.2.1 Root System Architecture and Plasticity
4.2.2 Root Length and Growth
4.2.3 Root Hairs and Mycorrhizae
4.3 Root Physiological Traits Determining the Acquisition of Potassium by Plants
4.3.1 Traits Related to Potassium Uptake and Depletion in the Rhizosphere
4.3.2 Traits Related to pH Modification in the Rhizosphere
4.3.3 Traits Related to Exudates in the Rhizosphere
4.4 Summary and Conclusions
References
Chapter 5: Potassium Use Efficiency of Plants
5.1 Metrics of Potassium Use Efficiency and Their Relationships
5.2 Differences in Potassium Uptake and Utilization Between Plant Species
5.2.1 Differences in KUpE Between Plant Species
5.2.1.1 Kinetics of Potassium Uptake
5.2.1.2 Root System Investment and Architecture
5.2.1.3 Rhizosphere Acidification and Root Exudates
5.2.2 Differences in KUtE Between Plant Species
5.3 Differences in Potassium Uptake and Utilization Within Crop Species
5.3.1 Differences in KUpE Within Plant Species
5.3.1.1 Kinetics of Potassium Uptake
5.3.1.2 Root System Investment and Architecture
5.3.1.3 Root Exudates
5.3.2 Differences in KUtE Within Crop Species
5.3.2.1 Partitioning of Potassium Within the Cell and Its Substitution with Other Ions
5.3.2.2 Partitioning and Redistribution of Potassium Within the Plant
5.3.2.3 Partitioning of Resources into the Economic Product
5.4 Breeding Crops for Greater Agronomic Potassium Use Efficiency
5.5 Conclusions
References
Chapter 6: Considerations for Unharvested Plant Potassium
6.1 The Crop Canopy as a Source of Potassium
6.2 Potential of Potassium Cycling by Crops and Cover Crops
6.3 Synchrony of Potassium Availability in Cropping Systems
6.4 Residue Potassium as a Means of Reducing Potassium Losses from the System
6.5 Potassium from Agro-Industrial Residues
6.6 Fertilizer Recommendations and Potassium Cycling
6.6.1 Modeling Potassium Release from Residues
6.6.2 Implications for Timing of Soil Sampling
6.7 Conclusion
References
Chapter 7: Considering Soil Potassium Pools with Dissimilar Plant Availability
7.1 Introduction
7.2 Solution Potassium and Potassium Activity
7.3 Surface-Adsorbed Potassium
7.4 Interlayer K in Micas and Partially Weathered Micas
7.5 Interlayer Potassium in Secondary Layer Silicates
7.6 Structural Potassium in Feldspar and Feldspathoids
7.7 Neoformed Potassium Minerals
7.8 Fixation and Release of Interlayer Potassium
7.8.1 Contractive and Expansive Forces
7.8.2 Factors Affecting Potassium Fixation and Release
7.9 Interpreting ``Exchangeable Potassium´´
7.10 Mineral Transformations
7.10.1 Reversible Changes in Interlayer Potassium
7.10.2 Implications for Building and Depleting Soil Fertility
7.11 Short-Term Transformations in the Rhizosphere
7.12 Nonexchangeable Potassium as a Functional Pool
7.13 Classifying Soils According to Their Potassium Behavior
7.14 Lessons Learned from Long-Term Experiments
7.15 Prognosis
References
Chapter 8: Using Soil Tests to Evaluate Plant Availability of Potassium in Soils
8.1 Sample Collection and Preparation
8.1.1 Vertical Stratification
8.1.2 Spatial Heterogeneity in Response to Agronomic Management
8.1.3 Sample Drying and Handling
8.2 What Are the Forms of Potassium in Soil?
8.3 How Is Potassium Released from Different Solid-Phase Forms?
8.3.1 Potassium in Fertilizer and Crop Residues
8.3.2 Surface-Adsorbed (Exchangeable) Potassium
8.3.3 Chemical Weathering
8.4 How Do Soil Tests Assess Plant-Available Potassium?
8.4.1 Soil-Test Development
8.4.2 Soil Tests for Assessing Soil Solution Potassium
8.4.3 Soil Tests for Assessing Surface-Adsorbed Potassium
8.4.4 Soil Tests for Dissolving Interlayer/Structural Potassium
8.4.5 Soil Tests that Combine Multiple Mechanisms of Potassium Dissolution
8.4.6 Soil Tests for Assessing the Rate of Solution Potassium Replenishment
8.5 Difficulties Relating Soil Test Potassium to Crop Acquisition
8.5.1 Rates of Resupply to Potassium-Depleted Zones Around Active Roots
8.5.2 Root System Architectures and Their Interaction with Soil Moisture
8.5.3 Variation in Root System Attributes that Allow Plants to Exploit Different Potassium Pools
8.5.4 Specificity of Soil Test Potassium-Crop Response Relationships and the Role of Trial Databases
8.6 Lessons Learned from Long-Term Experiments
8.7 Concluding Remarks
References
Chapter 9: Evaluating Plant Potassium Status
9.1 Visual Symptoms of Potassium Deficiency
9.2 Light Reflectance
9.3 Plant Tissue Chemical Content
9.3.1 Sufficiency Ranges (SR)
9.3.2 Diagnosis and Recommendation Integrated System (DRIS)
9.3.2.1 DRIS Chart
9.3.2.2 DRIS Indexes
9.3.3 The Modified DRIS System (M-DRIS)
9.3.4 Plant Analysis with Standardized Scores (PASS)
9.3.5 Compositional Nutrient Diagnosis (CND)
9.3.5.1 CND-clr
9.3.5.2 CND-ilr
9.3.6 Multiple Regression Approaches
9.3.7 Metabolite Profiles
9.3.8 Potassium Content in Plant Sap
9.4 Conclusions
References
Chapter 10: How Closely Is Potassium Mass Balance Related to Soil Test Changes?
10.1 Introduction
10.2 The Mass-Balance Approach
10.3 Temporal Nature of K Soil Test Values
10.4 Crop Residue Recycling in K Mass-Balance Considerations
10.5 Clay Chemistry and K Response
10.6 Relative Unresponsiveness in K Removal in Harvested Grain, Despite Wide Variability in Crop K Status and Responsiveness t...
10.7 Potassium Losses Due to Erosion from Wind and Water
10.8 Summary
References
Chapter 11: Assessing Potassium Mass Balances in Different Countries and Scales
11.1 Concepts of Soil Nutrient Balance
11.1.1 Potassium Removal and Use for Different Cropping Systems and Geopolitical Boundaries
11.1.2 Metrics for Nutrient Use Efficiency
11.1.3 Uncertainties in Estimating Nutrient Balances
11.1.4 Interpreting Nutrient Balance Information
11.2 Australia
11.2.1 Southern Australian Grain Farms
11.2.2 Trends in Potassium Removal
11.3 Southeast Asia
11.3.1 Data Sources and Limitations
11.3.2 Trends in Potassium Balance
11.4 China
11.4.1 Potassium Use and Crop Production
11.4.2 Potassium Balance Studies
11.4.3 Potassium Balances in Grain and Cash Crops
11.4.4 Spatial and Temporal Changes in Potassium Balance
11.5 India
11.5.1 Crop Requirement and Potassium Use
11.5.2 Potassium Balance at the Country Scale
11.5.3 Potassium Balance at the Cropping System Scale
11.6 Sub-Saharan Africa
11.6.1 Potassium Balance at Continental and Country Scales
11.6.2 Potassium Balance at the Regional Scale
11.6.3 Potassium Balance at the Farm Scale
11.7 North Africa
11.8 United States
11.9 Brazil
11.10 Southern Cone of Latin America
11.11 Conclusion
References
Chapter 12: Considerations for Selecting Potassium Placement Methods in Soil
12.1 Introduction
12.2 Factors Affecting Root Access to Zones of K Enrichment
12.2.1 Crop Root Distribution
12.2.2 Mobility of K in Soil in Soil Profiles
12.2.3 Movement of K to Plant Roots
12.3 Fertilizer K Application Strategies in Soil
12.4 Quantifying Fertilizer K Recovery
12.5 Crop Characteristics Influencing K Application Strategy
12.6 Soil Characteristics Influencing K Application Strategy
12.7 Conclusions
References
Chapter 13: Timing Potassium Applications to Synchronize with Plant Demand
13.1 Introduction
13.2 Why the Emphasis on Potassium?
13.3 The Need to Synchronize Potassium Supply with Plant Demand
13.4 Managing Potassium to Synchronize Supply with Plant Demand
13.5 Fertigation for Synchronized Potassium Supply
13.6 Use of Decision Support Tools
13.7 Future Thrusts
13.8 Conclusion
References
Chapter 14: Broadening the Objectives of Future Potassium Recommendations
14.1 Introduction
14.2 Soil and Tissue Testing
14.2.1 Soil Testing for Potassium
14.2.2 Tissue Testing for Potassium
14.2.3 Luxury Consumption of Potassium
14.3 Factors Influencing Potassium Uptake
14.3.1 Genetics and Potassium Uptake
14.3.2 Potassium Uptake and Yield
14.3.3 Potassium Uptake and Management
14.4 Alternative Potassium Management Strategies
14.4.1 Foliar Fertilization with Potassium
14.4.2 Potassium Application Methods, Including Fertigation
14.4.3 Recycling Potassium in Plants
14.4.4 Crop Residues and Potassium Nutrition
14.4.5 Fungal Associations and Potassium Nutrition
14.5 Impact of Potassium on Crop Quality
14.5.1 Potassium Nutrition and Crop Quality
14.5.2 Cereals
14.5.3 Oilseeds
14.5.4 Forage
14.5.5 Fiber
14.5.6 Tubers and Tuberous Roots
14.5.7 Fruits and Vegetables
14.5.8 Human Nutrition and Health
14.6 Plant Stress Tolerance and Potassium Nutrition
14.6.1 Potassium and Abiotic Stress Tolerance
14.6.2 Potassium and Biotic Stress Tolerance
References
Chapter 15: Improving Human Nutrition: A Critical Objective for Potassium Recommendations for Agricultural Crops
15.1 Potassium Intake Needs
15.1.1 Dietary Reference Intakes
15.1.2 Potassium Intakes Worldwide
15.2 Internal Balance of Potassium
15.2.1 Potassium Tissue Movement
15.2.2 Renal Potassium Handling
15.2.3 Interactions with Sodium Balance
15.3 Potassium Bioavailability
15.3.1 Kinetic Modeling and Potassium Bioavailability
15.4 Potassium and Hypertension
15.4.1 Mechanisms of Arterial Pressure Control
15.4.2 Potassium and Arterial Pressure
15.4.3 Epidemiological Data
15.4.4 Potassium Supplementation Studies
15.4.5 Dietary Intake Clinical Trials
15.5 Potassium, Diabetes, and Glucose Control
15.5.1 Potassium and Glucose Control
15.5.2 Potassium and Diabetes
15.6 Potassium and Bone
15.6.1 Potassium and Calcium Balance
15.6.2 Potassium Bone Turnover and Bone Mineral Density
15.7 Opportunities for Future Interdisciplinary Efforts to Improve Potassium Recommendations of Agricultural Crops
References
Thematic Glossary of Terms