Environmental Factors Nutrients K. Raja Reddy Krreddy@pss.msstate.edu Environmental and Cultural Factors Limiting Potential Yields Atmospheric Carbon Dioxide Temperature (Extremes) Solar Radiation Water Wind Nutrients (N and K) Others, ozone etc., Growth Regulators (PIX) Nutrients - Objectives The objectives of this lecture are to: Learn temporal trends in fertilizer usage (Major nutrients). Influence of major nutrients on plant growth and development. Major Nutrients Trends and some Statistics Trends in World Commercial Fertilizer Use Trends in U.S. Commercial Fertilizer Use (China, USA and India) 2 15 1 5 4 3 2 1 China US India 194 195 196 197 198 199 2 194 195 196 197 198 199 2 1
Trends in U.S. Commercial Fertilizer Use (Nitrogen, Potash and Phosphate) Trends in U.S. Total Commercial Fertilizer Use (Primary, Secondary and Micronutrients) 15 Nitrogen 1 Potash 5 Phosphate 195 196 197 198 199 2 Commercial fertilizer use depends on variety of factors: Soil Climate and weather Feasible technology Crop mix Crop rotations Technological change Govt. programs Commodity and fertilizer prices Affordability 6 55 5 45 4 35 3 25 2 195 196 197 198 199 2 Nutrient Supply and Plant Growth Major Nutrients and Their Influences Nitrogen Supply and Plant Growth Nitrogen and Crop Yield 2
Question: Leaf developmental response to N and elevated CO 2 Do processes within a crop vary in their response to nutrients? Rate of leaf development, 1/d -1.5.3.1 35 ppm 5 1.5 1.75 2. 2.25 2.5 2.75 Leaf Area at Leaf unfolding, cm 2 Leaf area, cm -2 12 11 1 9 8 7 6 5 4 3 2 1 Nitrogen and Crop Growth and Development 35 ppm Leaf growth response to N and elevated CO 2 Cotton leaf area at leaf unfolding 6 5 1.5 1.75 2. 2.25 2.5 2.75 1% N 2% N % N 2 4 6 8 1 12 14 16 18 Mainstem leaf number Caster mature leaf sizes N treatments were imposed when leaf 5 was just unfolding Nitrogen and Crop Growth and Development Cotton leaf growth response to N and elevated CO 2 RLER, cm 2 cm -2 d -1.15.1 5 RLER = Relative Leaf Expansion Rate 35 ppm 5 1.5 1.75 2. 2.25 2.5 Stem Extension Rate, cm d -1 Stem elongation response to N and elevated CO 2 5 4 3 2 1 35 ppm Stem Elongation Rate Response to N and elevated CO 2 Stem Extension Rate, cm d -1 35 ppm 5 1.5 1.75 2. 2.25 2.5 2.75 5 1.5 1.75 2. 2.25 2.5 2.75 3
Leaf photosynthetic response to N and elevated CO 2 Relative Rates of Photosynthesis Photosynthesis, µmol CO 2 m -2 s -1 5 4 35 ppm 3 2 1 5 1.5 1.75 2. 2.25 2.5 2.75 Relative Photosynthetic Rates 35 ppm 5 1.5 1.75 2. 2.25 2.5 2.75 Can we use one function for all processes in a given crop? Functional relationships cotton for growth and developmental processes Stem Growth Photosynthesis Leaf Development Leaf Growth 5 1.5 1.75 2. 2.25 2.5 leaf area Questions: Do species vary in their response to nutrients? How about functional groups such as C 3 versus C 4? Is there a difference between the functional groups in their response to nutrients? N and Photosynthesis Functional Groups N and Photosynthesis Several Crops Leaf photosynthesis Leaf photosynthesis.5 1.5 2. 2.5 3..5 1.5 2. 2.5 3. 3.5 4. 4
Fraction of the optimum N and Photosynthesis Several Crops Leaf photosynthesis.5 1.5 2. 2.5 3. 3.5 4. Swtichgrass - C4 Photosynthesis, mg CO2 m -2 s -1 3 2 1 Photosynthesis - Variability Among Species Response to Leaf Nitrogen Maize.5 1.5 2. 2.5 3. 3.5 Leaf Nitrogen, g m-2 Sorghum Cotton Sunflower Rice Soybean N and several crops Stem elongation rates 1.6 1.4 Stem elongation rate.5 1.5 2. 2.5 3. 3.5 4. Swtichgrass - C4 N and several crops Leaf area expansion rates Fraction of the optimum 1.4 Leaf area expansion rate Swtichgrass - C4.5 1.5 2. 2.5 3. 3.5 4. Summary and Conclusions Nitrogen Responses across Species and Processes Functional algorithms varied among crop species and even among crop species within a functional physiological group such as C 3 or C 4 species. Functional algorithms varied among crop processes for a given species. Among the growth, developmental and physiological processes, leaf growth was more responsive to leaf N than other processes in almost all crops. N also affects cell division and cell elongation process leading to a cascade of effects on several processes in plants, and finally yield. Potassium Supply and Plant Growth 5
Potassium Supply and Plant Growth <3.5 Potassium Cotton Growth 1.15.94.39 Visual Symptoms and leaf K, %.3 Fraction of Optimum Potassium and Cotton Growth and Development 1.6 1.4 Stem Elongation Photosynthesis Leaf Initiation Rates Leaf Growth -.5 1.5 2. 2.5 3. 3.5 Leaf K, % Photosynthesis and Environment Response to phosphorus Sub-to supra-optimal supply of Pi Summary and Conclusions Nutrient Responses across Species and Processes Functional algorithms or responses varied among crop species. Functional algorithms varied among crop processes for a given species. Similar to N effects, among the growth, developmental and physiological processes, leaf growth was more responsive to leaf K. The effects of P on various processes are less quantified to arrive a conclusion. 6