Miller, Nutrient

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1 Percent of Samples (%) Percent of Samples (%) Leaf K Leaf Mg /1/1 Impact of Maize Ear Leaf K and Macro-Nutrient Ratios on Grain Yield in the Midwest Robert O. Miller, Colorado State University Fort Collins, CO Tim J.Smith, Crop Smith Inc., Monticello, IL Plant Analysis Background Plant nutrient content has been classified in five ranges as it relates to yield. Corn ear leaf nutrients at growth stage VT represent a synopsis of plant nutrition at the end of the vegetative growth. Adapted from Brown, J. R Plant analysis. Missouri Agr. Exp. Sta. Bull. SB1 Miller, 15 Miller, Miller, 1 Smith and Bower, 15 Ceres Solutions Corn Leaf Sampling In 1 Ceres Solutions serving growers in Western Indiana began intensive sampling of maize ear leaves GS VT-R1 for nutrient status. Sampling: Area <. ha, plants. Fields ranged in: soil type, hybrid, population, fertility and crop management systems. Analysis included N, P, K, Mg, Ca, S, Zn, Mn, Fe, Cu, B, and Mo. Project continued 1-15, and included GS: V3, V5, V and VT. Miller, Smith and Bower, 15 Betsy Bower Ceres Solutions, IN Tim Smith Crop Smith Farmers City, IL Corn Ear Leaf Nutrients - IN Ear Leaf VT-R1 51 samples, years Nutrient Deficiency Threshold 1 Percent of Samples Deficient < Less Than N (%) < P (%) < K (%) < Mg (%) < Ca (%) <.3... S (%) < Zn (ppm) < Data Ceres Solutions, Lafayette, IN, corn ear leaf VT-R Miller and Bower, 15 Corn Ear Leaf K Frequency Plot Observations, GS VT-R1 Western Indiana % 1 K Purdue University, Deficient Leaf Mg (%) Sites Source: Betsy Bower, Ceres Solutions And Midwest Independent Samplers Miller, Smith and Bower, 15 Ear Leaf Nutrient Ratios K vs Mg R² = Leaf K Mg vs K R² = Leaf Mg Range sort analysis of VT-R1 corn ear leaf survey data from IN 1 indicates that with K deficiency (< %) there is a very significant exponential increase in leaf Mg. Sorting leaf Mg shows a significant but small decrease in K. 1 Data: Corn Ear Leaf VT, Ceres Solutions 13, 51 sites data grouped based on lab analysis uncertainty. These results show strong evidence that there is a clear effect of leaf K content on Mg and that deficiency results in rapid Mg accumulation. Are Leaf Nutrient Ratios Important? Miller, Smith and Bower, 15 1

2 N:Mg Ratio /1/1 Nutrients DRIS Norms for Corn Ear Leaves Elwali, A.M.O., G.J. Gascho, M.E. Sumner Agron J 77:5. Reference DRIS Norms Ratio Mean Std N:K Leaf Mg:K and N:Mg vs Yield 1 Contrast five KRx sites with highest and lowest Mg:K ratios, show substantial yield differences. 1 Sites Data limited: Leaf N > 3. % (Range ) High Mg:K Ratio Site Mg:K 1 N:Mg Yield 3 Low Mg:K Ratio Site Mg:K N:Mg Yield P:K.19.5 S:K.11.3 Ca:K.5.1 Mg:K.1. N:Mg Based on a high yielding corn subpopulation > 1. Mg of grain per hectare. Corn ear leaf Mg:K ratios values >.15, were classified as K deficient. Ratio Ratio bu/ac GIB NEL NIE BLA NEL Average stdev. 1.5 Ratio Ratio bu/ac BEK BEC LAR CAL CAL Average stdev Mg:K ratios based on maize ear leaf at GS VT-R1 reps, three states Elwali et al 195, critical ear leaf GS VT Mg:K.1 ±.; N:Mg value 1 ± 3.7 Low Population Site Difference bu/ac 3 Yield data KRx project, lb/ac K plots, replications. Miller, Smith and Bower, 15 Miller, Smith and Bower, 15 Grain Yield and Leaf Nutrient Ratios Leaf Nutrition vs Grain Yield 1 Cate Nelson analysis of 1 KRx sites shows two primary clusters, sites with < 1.5% K and N:Mg < 1 and sites with K > 1.5 %, N:Mg >1. Parsing maize grain yield 1 by ear leaf ratios, shows 3% of yield is explained by leaf N, N:Mg > 1 (green) at ten sites. Six sites with N:Mg < 1 (red), averaged bu/ac lower yields Year Yield Difference bu/ac Relationship is consistent across years. Control Plot Yield (bu/ac) N:Mg Ratio > 1 N:Mg Ratio < 1 y = -x + 5x - 73 R² =.3 R² = Ear Leaf N GS VT-R1 (%) N:Mg Ratio 3 Analysis < 1 > 1 N %.9.95 K % 1.5. Mg.35.3 Mg:K..1 N:K N:Mg Mean results based on N:Mg Ratio. 1 1 KRx control plot grain yields 1 sites, states, replications. Sites vary in hybrids, tillage, soil types and crop history. Miller, Smith and Bower, 15 Miller, Smith and Bower, 15 Conclusions Summary Liebig: Law of the Minimum Additional Research is planned for 1 in IN, IL IA and MN. Assessing corn leaf GS (VT-R1) nutrients based on analysis uncertainty proves useful for evaluating ratios. Ear leaf ratios established by Elwali (195) are effective for assessing deficiencies, despite shifts in cultural practices (hybrids, tillage population and fertility Mgt). Unique relationships exists for maize ear leaf N, K, Mg and lesser extent Ca, whereby K deficiencies (<.%) result in increased Mg, resulting in higher Mg:K, lower N:Mg and N:Ca ratios. Maize grain yields, based on 7 Midwest site years, are optimum when ear leaf ratios Mg:K <.15 and N:Mg ratios > 1, and sites outside these ranges show significant limitations on grain yield. s/assets/images/law%of%minimum.jpg That nutrient most limiting has the greatest nutritional impact on yield. Macro nutrients with the greatest concentration have the greatest impact: i.e. N, K, P, S, Mg, and Ca on corn vegetative growth. Six years of corn ear leaf data indicates macro nutrient deficiency dominates fertility issues. Micro deficiencies are rare when macros are in the optimum range. Critical nutrient ratios (Mg:K, N:Mg, N:S), are indicators of nutrient imbalances within the optimum range. Miller, Smith and Bower, 15 Miller, Smith and Bower, 15

3 Leaf K Leaf N LEaf Mg (%) Yield Nutrient Content /1/1 Corn Ear Leaf Nutrition Ranges Thank you for your time and attention 1 9 Corn Yield Optimum Range 75 Hidden Hunger High 3. % Nitrogen 3. % 5. % Potassium.7 % 1. % Phosphorus.3 % 5 Deficient.1 % Sulfur. % Excessive Nutrient Supply Miller, Smith and Bower, 15 Modified from Brown, J. R Plant analysis. Missouri Agr. Exp. Sta. Bull. SB1 Leaf Mg:K and N:Mg vs Yield 1 Contrast five KRx sites with highest and lowest Mg:K ratios, show substantial yield differences. 1 Sites Limited: Leaf N > 3. % (Range ) High Mg:K Ratio Site Mg:K 1 N:Mg Yield 3 Ratio Ratio bu/ac GIB NEL NIE BLA NEL Average stdev. 1.5 Low Mg:K Ratio Site Mg:K N:Mg Yield Ratio Ratio bu/ac BEK BEC LAR CAL CAL Average stdev Low Population Site Difference bu/ac Analysis of Observational Data Lab Measurement Uncertainty Leaf N % Are these lab values different? Intra - Lab Uncertainty N % ±.5 P % ±.1 K % ±.5 Mg % ±. 3 laboratories providing results. Within lab uncertainty based on a-.5 and 3 replications. Data Filtering Data was parsed based on lab uncertainty ranges. For this study we used ±.5% for K. Data was filtered to remove N deficiencies and excess N (>.%). 1 Mg:K ratios based on maize ear leaf at GS VT-R1 reps, three states Elwali et al 195, critical ear leaf GS VT Mg:K.1 ±.; N:Mg value 1 ± Yield data KRx project, lb/ac K plots, replications. Miller, Bower, & Smith, 15 Miller, Bower, & Smith, 15 Ear Leaf Nutrient Ratios Corn Ear Leaf K vs Mg Plant nutrition is based on minimum sufficiency, whereby adequate is not yield limiting. Nutrient ratios provide insight on interactions and impact of individual nutrients on potential yield. Observations: Western IN 11, GS VT-R1, 51 sites High Mg associated with very high leaf Ca > 1.% and/or high B, > mg/kg.5. N vs K K vs N..3. K y = -.1x + 1.9x R² = Leaf N. y =.11x R² = Leaf K.1 N <.7% N >.% Data: Corn Ear Leaf VT, Ceres Solutions 13, 51 sites data grouped based on lab analysis uncertainty. Miller, 15 Miller, Bower, & Smith, 15 3

4 LEaf Mg (%) Mean Leaf Mg (%) Yield Nutrient Content Mean Leaf Mg (%) Mean Leaf N (%) Mean N:Mg Ratio /1/1 SdDwkNLReh-r-3yh9vrbN1W7rXhM9ILwyYFz_gXtMO 1 9 Corn Yield Macros and micro impact on corn Luxury Consumption 75 Hidden Hunger High Deficient Excessive Nutrient Supply vspfiles/assets/images/law%of% Miller, minimum.jpg Smith and Bower, 15 Corn Ear Leaf K vs Mg Observations: Western IN 11 Ear Leaf GS VT-R1 51 samples, N limited:.7 > N <.; Data sorted by K, uncertainty K ±.5% y = -.1x 3 +.1x -.7x R² = Miller, Bower, & Smith, 15 Stdev With decreased K, there s an exponential increase in Mg, across sites and management systems. Corn Leaf K vs Mg, N and N:Mg Observations: Western IN 11 Ear Leaf GS VT-R1 51 samples, N limited:.7 > N <.; Data sorted by K, uncertainty K ±.5% Stdev K vs Mg R² = Stdev K vs N R² = With decreased K, exponential increase in Mg and curve linear decreases for N and N:Mg K vs N:Mg R² = Stdev Miller, Bower, & Smith, 15 Corn Ear Leaf K vs Mg Observations: Western IN 11, GS VT-R1, 51 sites Corn Ear Leaf Nutrients 1 Growth Stage VT-R Observations are across hybrids, populations, soil types, fertility and management systems similar climate Analysis Critical Percent Deficient (%) Level 1 Iowa Nebraska 3 Minnesota N (%) < P (%) < K (%) < Mg (%) < Ca (%) < S (%) < Zn (%) < Deficiency Most Frequent: K source Iowa survey Midwest Independent Soil Samplers, 31 fields 3 source: Nebraska survey 5 fields, Minnesota, survey fields Miller, Bower, & Smith, 15 Miller, Bower, & Smith, 15

5 K lbs/ac/day /1/1 Corn Ear Leaf Nutrients - IN Corn Potassium Accumulation Rate 1 Ear Leaf VT-R1 1, 1 samples Nutrient Percent of Samples Nutrient Deficient P K Mg S B Zn Threshold 1 <. < 1.7 <.1 <.1 < 5 < K Uptake Peaks Yield bu/ac K lbs/ac/day Low N Sites < 3.1 (%) High N Sites > 3. (%) *above ground Days After Planting Data Ceres Solutions, corn ear leaf VT-R V V V1 VT R1 R Miller and Patterson, 15 1 Calculated from: Karlen, Flannery, and Sadler. 19. Agron J. :3-. Miller, 13 Summary K Fertility K Research Project Corn K uptake is demand driven: population, growth and nitrogen. STK provides insight on probability of crop response. K uptake from the soil is as much about the question of how much is about crop demand, and when! KRx project was launched in 11 to evaluate grain yield response to applied K across states, 7 sites over four years. Assess STK, ear leaf nutrient and K fertilizer on grain yield. Robert Nielsen, 9, Purdue University _35555_3173_n.jpg K Deficiency Winchester, Indiana, 1 - Dave Taylor Miller and Bower, 1 Miller, Bower, Smith, 15 K RX Corn Research STK Dry vs Moist Yield Results a study was conducted across 7 sites in six states to evaluate response to K. K was applied at, 5, 1 lbs/ac at growth stage V3 V5, ranging 1,, plts/ac, eight replications. STK sampled at planting, corn ear leaves were sampled at VT, and grain yield and moisture determined based on 3/1th acre of each plot at black layer. Rs of Fertility Time Place Material Rate Robert Nielsen, _35555_3173_n.jpg Contrast comparison of soil STK of five lowest sites and five and highest sites, 1 KRx research locations. Test Parameter Low Range STK Dry STK Moist High Range Delta STK - (ppm) Yield (bu/ac) 1 K Response (bu/ac) STK - (ppm) Yield (bu/ac) K Response (bu/ac) Data: 1 sixteen locations sorted by STK value, yield based control plots and response to K 5 lbs/ac. Miller, 1 Miller, 15 5

6 Leaf Mg N:Mg Ratio Yield Response bu/ac /1/1 What are you looking for? I lost my keys over by that car. Then why are you looking for them there? Because this is where the light is. K RX Ear Leaf K vs Yield A relationship between corn ear leaf K at VT and yield response to applied K, 3 sites The fate of the scientist: Only searching where there is light (or where we want to see). Dr. Michael Rutzke, Ph.D. Department of Crops & Soil Sciences, Cornell University Ithaca, NY % 1% Corn Ear Leaf K VT-R1 (%) Yield response to applied K Leaf K < 1.5%, % responsive to K application Miller, 15 Corn Ear Leaf K vs Mg:K, Iowa 1 Preliminary: Relation of leaf Mg:K ratio to based corn yield y = -.95x x x R² = Site 1 N % K % Mg:K Yield bu/ac NIE NEL BEK THO CAL Replications per site. Requirement: N sufficiency must be met when assessing Mg:K ratio, need to include N:Mg Leaf K Miller and Bower, 15 Leaf Mg:K and N:Mg vs Yield 1 Contrast five KRx sites with highest and lowest leaf Mg:K ratios, show substantial yield differences. 1 Sites Limited: Leaf N > 3. % (Range ) High Mg:K Ratio Site Mg:K 1 N:Mg Yield 3 Ratio Ratio bu/ac GIB NEL NIE BLA NEL Average stdev. 1.5 Low Mg:K Ratio Site Mg:K N:Mg Yield Ratio Ratio bu/ac BEK BEC LAR CAL CAL Average stdev Mg:K ratios based on maize ear leaf at GS VT-R1 reps, three states Elwali et al 195, critical ear leaf GS VT Mg:K.1 ±.; N:Mg value 1 ± Yield data KRx project, lb/ac K plots, replications. Low Population Site Difference bu/ac Miller, Bower, & Smith, 15 Yield and Leaf Nutrient Ratios KRx Conclusions Cate Nelson analysis of 1 KRx sites 1 shows two primary clusters, sites < 1.5% K and N:Mg < 1 and sites with K > 1.5 %, N:Mg > N:Mg Ratio Yield Differences Results show side dress K response at % of 7 research sites over four years in the Midwest Year bu/ac STK levels < 15 ppm are highly responsive, 15 ppm moderately responsive (5%), -3 ppm minimal responsive (37%) to side dress K Data: Corn Ear Leaf VT K and N:Mg ratio, Relationship consistent across years. Additional Research is planned for 15 in IN, IL IA and MN. 7 Midwest site years, grain yields are optimum when ear leaf K < 1.9%, ratios Mg:K <.15 and N:Mg ratios > 1. Sites outside these leaf ranges show significant limitations on yield. Corn yield data bases on control plot yield replications. Miller, Bower, & Smith, 15 Miller Bower and Smith, 15

7 /1/1 Why STK Issues K Nutrition Driving Factors STK is estimate of K supply, based on probability of response Daily Growth Rate 5 Vegetative Biomass Population: greater density, increase K uptake, reduced soil volume per plant. Grain Biomass Plant growth and therefore K uptake, is demand driven Nitrogen: drives growth rate, and K demand. Demand is set by population and is growth stage specific depth -1 DM Kg/ha/day STK does not estimate soil K rate lbs/ac/day 15 STK Level: higher values improve uptake. Yield: higher yields increase K removal per yr. 1 Tillage: reduced tillage increase K stratification. Limits on soil K diffusion/supply V5-V1, result in Mg substitution 5 13 Temperature: higher temps, faster growth rate, greater daily demand. 3 Impact Yield 1 Days After Emergence 1 - Law of Unintended Consequences Miller, 15 Recommendations Miller, 15 Grain yield Response to K Assess sub soil K levels (- or - ). STK 1-1 indicate possible response, < 1 ppm likely response. Assess at 1-% of grid points. If your not looking for it...you ll never find it! Plant Analysis. Ear leaf (VT-R1) K < 1.9%, Mg:K ratios >.1 and N:Mg ratios < 1 are indicative of K deficiencies. Track annually to assess K mgt effectiveness. Mike Lindaman, Boone IA Focus K fertilizer on subsoil applications side dress. Surface broadcast applications, ineffective. Don t expect to change STK or leaf K in 1 year, longer term - yrs. High corn population and yields (>35, plts/ac), push K uptake and reduce root volume/plant. Adjust fertility. Miller, 15 Acknowledgements Jessica Hagy: R Miller, Miller, 7 //-things-to-say-before-you-die/3/ Recommendations Craig Struve, MISS, IA Tom McGraw, MISS, IA retired Betsey Bower, Ceres Solutions, IN Management Tool Larry Eekhoff, New Cooperative, IA Potassium Soil Test Jodi Jaynes, Sure-Tech Laboratories, IN Sub Soil K Test Larry May, Lincoln, NE Tissue Test Recommendation Optional Tim Eyrich, Winfield Solutions, NE Mike Lindaman, Ag Source LGI Lab, IA Larry May, Lincoln, NE Assess sub soil K levels (- or - ). STK 1-1 indicate possible response, < 1 ppm likely response. Assess at 1-% of grid points. Ray Ward, Ward Laboratories, NE Plant Analysis. Ear leaf (VT-R1) K < 1.9%, Mg:K ratios >.1 and N:Mg ratios < Don Meyers, Rock River Lab, WI 1 are indicative of K deficiencies. Track annually to assess K mgt effectiveness. Focus K fertilizer on subsoil applications side dress. Surface broadcast applications due little. Don t expect to change STK or leaf K in 1 year, longer term - yrs. Miller, 15 High corn population and yields (>35, plts/ac), push K uptake and reduce root volume/plant. Adjust fertility. 7

8 DM Kg/ha/day Dry Matter lbs/ac Dry Matter lbs/ac/day /1/1 Summary Connecting the Dots Ear Leaf K Show 15-% K Deficiencies VT-R1 VT-R1 Leaf Ratios High Mg:K, Mg:K & N:K suggest lower yields Monitor the leaf History Increasing Yield, Grain Removal Decreasing Root Volume/ plant Population K Uptake 7.5 Max K Uptake lbs/ac/1 plts Corn V-V1 K -1 bu/ac/day bu corn Root Uptake Diffusion is main mechanism Rhizosphere zone -1.5 cm Drought Reduces K vs Mg Diffusion of K limited Mg Uptake Increases Drought Factor KRx Sidedress Grain Increase with K, % probability Soil K Supply Soil K Release + Diffusion Rate critical lbs/ac/day bu/ac corn K Management Follow Rs for K Time, Place, Amount Product KRx What we ve Learned STK Four Ranges: of STK <15, 15-, -3, > 3 ppm. Sidedress K yield response % on low STK sites, but sites - 3 ppm showed 37% response. Nutrient Stratification is substantial, reduced tillage has stratified K and P at -, sub soils show strong depletion > % of KRx sites. Side dress K at - depth Corn Leaf: K, Mg:K, and N:Mg, are indicative of lower corn yield potential, and greater likely hood of K response. When soil K diffusion-supply is limited greater potential of Mg and Ca uptake. Miller, 1 Miller, 15 Corn Growth and Nutrition Corn K Demand (lbs/ac) = f (Population) (N Nutrition) (Temp) Vegetative Biomass Grain Biomass 1 1 Days After Emergence These three primary factors drive nutrient demand. When soil rhizosphere K diffusive - supply is limited, during V5-VT rapid growth, there is a Mg substitution for K (lesser extent Ca) which impacts vegetative biomass, and ultimately limits grain fill potential. jpg Tillage Reduced and No-Till systems stratify nutrients at the soil surface. Example - sample 133 ppm vs 1- sample 9 ppm. Results is greater subsoil depletion of K. Soil: ALP, Chelsea F. loamy sand, Independence, IA 1 Calculated from Sayre, 19, Plant Phys Miller Bower and Smith, 15 Miller, 11 K Summary Corn Growth: Sayre 19 1 Miller, 1 Apply K fertilizers in in spring or in season, follow the Rs of soil fertility. Sample sub soil (-1 ) for STK. Values < 1 ppm are indicative of higher probability of response Tissue leaf test at V3, V5 and/or VT-R1. Assess if nutrient ratios are within acceptable range. Consider side dress K applications. Probability N:K Mg:K Ca:K Ratio > 1.9 >.15 >.5 Moderate High Very High Plant Population: 1,7 Yield: 1 bu/ac Sigmoid Growth Curve R1 5 R² = Day 1 1 Days after emergence 1 Calculated from Sayre, 19, Plant Phys Miller, 13

9 lbs/ac K lbs/ac/day N lbs/ac/day Dry Matter (lbs/ac) N lbs/ac/day Total K Uptake lbs/ac /1/1 Corn Nitrogen Accumulation Ear + Shank Stalk Corn Yield: 3 bu/ac Upper Leaves 5 Lower Leaves e.com/t5/image/serverpage /imageid/71ifb55bf19a /imagedimensions/3x3/ismoderationmode/false?v=mpbl-1 % Corn Nitrogen Accumulation Rate N Uptake Peak Ear + Shank Stalk Upper Leaves Lower Leaves %... 5 *above ground GDD 1% 1% *above ground Days After Planting 1 Calculated from: Karlen, Flannery, and Sadler. 19. Agron J. :3-. Miller, 13 1 Calculated from: Karlen, Flannery, and Sadler. 19. Agron J. :3-. Miller, 13 Corn Growth: Sayre 19 1 Corn Dry Matter Accumulation: Karlen et al 19 1 The N accumulation rate was maximum at pollination, at a rate of. lbs/ac/day. The K accumulation rate was maximum at days at an average rate of 3. lbs/ac/day, lasting for 1 days. Peak K accumulation rate proceeded peak N uptake by 1 days, and decreased to near zero at days Days After Emergence Calculated from Sayre, 19, Plant Phys Wooster, OH 19. Miller, 13 N K 3, 5,, 15, 1, 5, *above ground nine sampling dates Corn Yield: 3 bu/ac GDD 1 Calculated from: Karlen, Flannery, and Sadler. 19. Agron J. :3-. Miller, 13 Corn: Population, Yield and K Uptake Corn Population vs K Uptake 1 Source / Year Population Yield Total K uptake plants/ac bu/ac lbs/ac Sayre, 19 1, Jordan et al, 195 1, 7 Hanway, 19 17, Rhoads and Stanley, 191, 3 Karlen et al, 19, 3 31 Doberman, 1 3, 3 73 Bender et al, , K per unit yield 1 lbs/bu 1 Cassman (3), Optimum K Accumulation.95 to 1.1 lbs of K per bushel of grain. Comment, Plots received fertilizer applications prior to growth stage R1, total 1 lbs/ac. 3 Note, soil test K was 153 ppm, there was no reported use of K fertilizer. Total K uptake per plant g /plant * 1.9* Miller, g K per plant y =.77x R² =.1 1,, 3,, 5, Corn Population (plts/ac) 1 Source of data: Sayre, 19; Jordan et al 195; Hanway, 19; Rhoades and Stanley 191; Karlen et al 197; Karlen et al 19; and Doberman, 3. Individual plant K accumulation estimate is 3.1 g per plant across 5 years of research Miller, 13 9

10 GDD Soil Depth in K lbs/ac/day /1/1 Corn Yield: Max K Uptake Rate Corn Nutrient Uptake Dynamics Yield 1 Environment Population Yield Total K Uptake Max K Uptake Rate plants/ac bu/ac lbs/ac lbs/ac/day Low 7, High 3, Results from 19, Florence, SC, site had Mehlich 1 K of 7 mg/kg and received 15 lbs/ac K over multiple applications. Source: Karlen, Sadler and Camp, Agron J. 79:9-5. Max K uptake rate is proportional to yield potential,. lbs/bu/day for bu corn Corn Development Dry Matter 1 N Uptake Stage GDD Range lbs/ac/day P Uptake K Uptake V V V7 V V1 V R1 R R R Calculated from: Karlen, Flannery and Sadler. 19. Agron J. :3-. Miller, 13 Miller, 13 Impact of GDD on Corn Development 1 Impact of GDD impact Corn Development per. Mov. Avg. (Series1) 1 5 per. Mov. Avg. (Series) /1 /1 5/11 5/31 / 7/1 7/3 Day / Month 1 Champaign, Illinois Weather station, 5 day average. Mon/Day 9 1 GDU GDU Apr Apr May May Warm springs (1) result in higher soil temperatures, and increased GDDs per day during early growth, resulting in faster corn development and increased uptake per day. Miller, 13 Corn Root Growth Corn root growth is exponential for 1 st five weeks after emergence, then linearly till tassel, and decreases to black layer. Depth 3 cm from V VT. Impact on Nutrients? Mengel and Barber, 197 Agron J :31-3 (197) Miller, 13 K Accumulation and Root Growth (Modeled) Ear Stalk Upper Leaves Lower Lvs Karlen et al, Root Density cm/cm 3 Mengel and Barber, Max rate 5-5 days Accumulation % of total K uptake. Days After Planting Miller, 13 1

11 Plant root /1/1 Mechanisms of Root Nutrient Uptake The mechanisms of nutrient uptake are: mass flow; root interception and diffusion. K+ Root Interception: Root contact with nutrient ion. Accounts for less than % of uptake. Mass Flow: Nutrients acquired through mass flow of soil water to plant root Soil Nutrient Diffusion Profile K+ Mg++ Initially, diffusion supplies a large quantity of nutrient, but with rhizosphere depletion the rate decreases, see Figure below. Over time the zone of depletion extends outward and diffusion supply decreases. Diffusion decreases with soil moisture content and temperature; and increases with K supply and dissolved O. Mg ++ Ca ++ Diffusion: Nutrient movement down ion concentration gradient to form bulk soil to zone of root depletion. Distance from root (mm) Ca++ Rb rhizosphere depletion by corn roots Miller, 1 Miller, 13 Miller, 13 1 Jungk and Claassen, 19. Z. Pflanzenernaehr. Bodenk Soil K Diffusion Integrating Crop Development and Soil Fertility Extractable K diffusion extends up to 7 mm fromm the root surface declining along a logarithmic function. Thus can nutrient diffusion from a soil volume of L (1. ft 3 ) through a season provide corn (based on a population of 3, plts/ac) grams of K 1 per plant? 3, 5,, 15, 1, 5, Rape roots K removal after seven days. Nonexchangeable K, as measured by HCL extraction, is depleted by plant root hairs in the near rhizoshpere extending.5 mm There was no rhizosphere Mg diffusion, and Ca showed elevated concentrations in the 1-3 mm zone. Assuming a yield goal of bu/ac and a max K uptake of lbs/ac/day, can soil K diffusion provide.1 g/plt/day of K? Can soil diffusion continue to meet peak nutrient uptake during vegetative growth with a population growth rate of 35/plt/yr? Soil testing needs to focus on supply rate Based on relationship between K uptake and plant population. Assumes. lbs per bushel per day relationship between max K uptake rate and yield. 1 Jungk and Claassen, 19. Z. Pflanzenernaehr. Bodenk Miller, 13 Miller, 13 Corn Tissue Analysis Research Robert O. Miller, Colorado State University, Fort Collins, CO KR X STK: Dry vs Wet by Depth ISU has re-introduced the STK wet method Site HAL BON STO 15 Yield / Delta * bu/ac Depth (in) Soil Test K (ppm) Dry Wet Dry Wet Dry Wet Treatment application of 5 lbs/ac K at V-V. * Grain responsive sites Significant STK stratification Dry and Wet STK decrease with depth, but equal probability of yield response Miller, 13 Miller, 1 11

12 LEaf Mg (%) Percent of Samples (%) Percent of Samples (%) /1/1 Corn Ear Leaf VT Tissue Nutrients Analysis International 1 US (sufficiency) Marginal Adequate Univ. Kentucky Purdue Univ. 3 Corn Tissue Research Corn ear leaf nutrients at growth stage VT represent a synopsis of plant nutrition at the end of the vegetative stage. N (%) P (%) K (%) Mg (%) Ceres Solutions, surveyed corn leaf tissue nutrients at 3 growth stages in 1, expanded in 11, and in 1 study conducted in IN and IA. Ca (%) S (%) Zn (ppm) Reuter and Robinson, Robert Nielsen, 9, Purdue University _35555_3173_n.jpg Miller and Bower, 13 Miller and Bower, 13 Ceres Solutions Corn Leaf Sampling In 1 Ceres Solutions serving growers in Western Indiana began intensive sampling of maize ear leaves GS VT-R1 for nutrient status. Sampling: Area <. ha, plants. Fields ranged in: soil types, hybrids, populations, fertility and crop management systems. Analysis included N, P, K, Mg, Ca, S, Zn, Mn, Fe, Cu, B, and Mo. Project continued through 1, and included GS: V3, V5, V and VT. Miller, Bower, Smith, 15 Betsy Bower Ceres Solutions, IN Tim Smith Crop Smith Farmers City, IL Corn Ear Leaf K Frequency Plot Observations, GS VT-R1 Western Indiana % 1 K Purdue University, Deficient Leaf Mg (%) Sites Source: Betsy Bower, Ceres Solutions And Midwest Independent Samplers Miller, Bower, & Smith, 15 Corn Ear Leaf K vs Mg Observations: Western IN 11, GS VT-R1, 51 sites Observations are across hybrids, populations, soil types, fertility and management systems similar climate Analysis of Observational Data Lab Measurement Uncertainty Leaf N % Are these lab values different? Intra - Lab Uncertainty N % ±.5 P % ±.1 K % ±.5 Mg % ±. 3 laboratories providing results. Within lab uncertainty based on a-.5 and 3 replications. Data Filtering Data was parsed based on lab uncertainty ranges. For this study we used ±.5% for K. Data was filtered to remove N deficiencies and excess N (>.%). Miller, Bower, & Smith, 15 Miller, Bower, & Smith, 15 1

13 P (%) Mean Leaf Mg (%) LEaf Mg (%) S (%) Mean Leaf N (%) Cu (ppm) Mean N:Mg Ratio B (ppm) Mean Leaf Mg (%) Mean Leaf Mg (%) /1/1 Corn Ear Leaf K vs Mg Corn Ear Leaf K vs Mg Observations: Western IN 11, GS VT-R1, 51 sites N <.7% N >.% High Mg associated with very high leaf Ca > 1.% and/or high B, > mg/kg K.5 Observations: Western IN 11 Ear Leaf GS VT-R1 51 samples, N limited:.7 > N <.; Data sorted by K, uncertainty K ±.5% Stdev.1 y = -.1x 3 +.1x -.7x R² = With decreased K, there s an exponential increase in Mg, across sites and management systems. Miller, Bower, & Smith, 15 Miller, Bower, & Smith, 15 Corn Leaf K vs Mg, N and N:Mg Observations: Western IN 11 Ear Leaf GS VT-R1 51 samples, N limited:.7 > N <.; Data sorted by K, uncertainty K ±.5% Stdev K vs Mg R² = Stdev K vs N R² = With decreased K, exponential increase in Mg and curve linear decreases for N and N:Mg K vs N:Mg R² = Stdev Miller, Bower, & Smith, 15 Corn Ear Leaf Three Years Western Indiana, three years Analysis uncertainty K ±.5% Upper limit Elwali Mg:K Ratio R² =.97 R² =.9919 R² = Mg:K relationship is consistent across years, more pronounced with higher temps during GS 5-VT (1), less in cooler years (11). Year GDU 1 Precip Period May 1- June 3, F and inches Miller, Bower, & Smith, 15 Corn Leaf Nutrient Ratios Observations: Western IN 11 Ear Leaf GS VT-R1 51 samples, Data sorted by N, uncertainty N ±.5% N vs P R² = N (%) Stdev N vs S R² = N(%) Stdev N vs Cu R² = N (%) Stdev N vs B R² = N (%) Stdev Magnesium Uptake vs Potassium Content in Rhizo-Solution Time course of Mg and K uptake by ryegrass Mg uptake suppressed by K > 5 um in soil-grown systems. As K is depleted in the rhizosphere Mg uptake increases. Maize, as K supply decreases V5-VT, substitution of Mg increases, impacts growth. With increased N: curve linear increases in P, S, and Cu, no relationships shown for B. S is most significant. 1 Seggeweiss and Jungk, 19. Z. Pflanzenernaehr. Bodenk Miller, Bower, & Smith, 15 Miller, Bower, Smith, 15 13

14 DM Kg/ha/day Leaf N:K Ratio /1/1 Does Mg:K and N:Mg Impact Corn Yield KRx project was launched in 11 to evaluate grain yield response to applied K across states, 15- sites/yr. Assess ear leaves nutrient ratios at VT-R1 on grain yield of control plots. Leaf Mg:K and N:Mg vs Yield 1 Contrast five KRx sites with highest and lowest Mg:K ratios, show substantial yield differences. 1 Sites Limited: Leaf N > 3. % (Range ) High Mg:K Ratio Site Mg:K 1 N:Mg Yield 3 Ratio Ratio bu/ac GIB Low Mg:K Ratio Site Mg:K N:Mg Yield Ratio Ratio bu/ac BEK NEL NIE BEC LAR Low Population Site BLA CAL NEL Average stdev. 1.5 CAL Average stdev Difference bu/ac Robert Nielsen, _35555_3173_n.jpg 1 Mg:K ratios based on maize ear leaf at GS VT-R1 reps, three states Elwali et al 195, critical ear leaf GS VT Mg:K.1 ±.; N:Mg value 1 ± Yield data KRx project, lb/ac K plots, replications. Miller, Bower, Smith, 15 Miller, Bower, & Smith, 15 Conclusions Summary Additional Research is planned for 15 in IN, IL IA and MN. Assessing corn leaf GS (VT-R1) nutrients based on analysis uncertainty proves useful for evaluating ratios. Ear leaf ratios established by Elwali (195) are effective for assessing deficiencies, despite shifts in cultural practices (hybrids, tillage population and fertility Mgt). Unique relationships exists for maize ear leaf N, K, Mg and lesser extent Ca, whereby K deficiencies (<.%) result in increased Mg, resulting in higher Mg:K, lower N:Mg and N:Ca ratios. Maize grain yields, based on 1 Midwest site years, are optimum when ear leaf ratios Mg:K <.15 and N:Mg ratios > 1, and sites outside these ranges show significant limitations on yield. Corn Growth and Nutrition Corn K Demand (lbs/ac) = f (Population) (N Nutrition) (Temp) Vegetative Biomass Grain Biomass 1 1 These three primary factors drive nutrient demand. When soil rhizosphere K diffusive - supply is limited, during V5-VT rapid growth, there is a Mg substitution for K (lesser extent Ca) which impacts vegetative biomass, and ultimately limits grain fill potential. jpg Days After Emergence Miller Bower and Smith, 15 1 Calculated from Sayre, 19, Plant Phys Miller Bower and Smith, 15 Corn Moisture and Nutrient Stress June 1, Eastern Indiana, Dave Taylor. Corn Ear Leaf K vs N:K Ratio Observations: Indiana 11, Stage VT, 3 Field Sites High N:K associated with very high leaf N levels, >.% Low N:K associated with N <.% Data: Betsy Bower, Ceres Solutions Miller and Bower, 13 1

15 Mg % Growth as Percent of Maximum /1/1 Plant Analysis Performance - Macros ALP SRB-11, Corn Leaf Analysis Median N % 3.1 P %.3 K %. S %. Ca %.7 Mg %. Intra - Lab Uncertainty ±.5 ±.1 ±.9 ±.17 ±. ±. All laboratory analyses have uncertainty which impacts the interpretation of N:K ratio. For this study we used ±.5% K Magnesium Uptake vs K Content in Rhizo-Solution Time course of Mg and K uptake by ryegrass Mg uptake surpresed by K > 5 um in soil-grown systems. As K is depleted in the rhizosphere Mg uptake increases. Corn ear leaves, as soil moisture content decreases, K depletes in near rhizosphere and Mg uptake increases. 3 laboratories providing results. N Results based on Dumas N Within lab uncertainty based on a-.5 and 3 replications. 1 Seggeweiss and Jungk, 19. Z. Pflanzenernaehr. Bodenk Miller, 13 Miller, 13 K and Mg Observations Indiana 11 Nutrient Critical Values Indiana 11 Ear Leaf at VT, K and Mg Deficiency Marginal Adequate High Toxic.9 Grower Site K % Mg % Oscars Miller Transition zone (symptoms or no symptoms) Potter Hill & Flat 1..3 Adams K % Deficient zone (symptoms) Leaf >.% Mg Growth Reduction? Shultz.75. Harold RN Home S Very low corn ear leaf K sites associated with high Mg, High K sites associated with low Mg. Competitive Replacement Critical Concentration Defined by Experimentation Concentration of Nutrient in Tissue (dry basis) Miller, 13 Modified from Reuter and Robinson, Miller, 13 Corn Potassium Research K RX Experiment 11-1 a study was conducted across the corn belt to evaluate grain response to K. At locations K was applied three rates at growth stage V V, across sites ranged with 1,, plts/ac. Principle of the Rs K was applied at corn growth stage V-V using spoke wheel injector at rates of, 5 or 1 lbs K per acre. Plots were 15 ft x 3 ft, eight replications. Corn ear Leaves were sampled at VT, and grain yield and moisture determined based on 3/1 th acre sampling of each plot at black layer. Robert Nielsen, _35555_3173_n.jpg Miller, 13 Miller,

16 /1/1 KR X Corn Yield Response KR X Corn Yield Response Krx Project Yield Results 11 Six Iowa and Nebraska sites. Site STK Check +K Increase Cty / State ppm bu/ac Cherokee, IA * K effect on ear size Check 1 Krx Project Yield Results 1 Six Iowa sites Site STK Check +K Increase Cty / State ppm bu/ac Pocahontas, IA K effect on ear size Check 139 Calhoun, IA * Palo Alto, IA * Webster, IA Calhoun, IA Webster, IA * Wright, IA * O Brien, IA Hamilton, NE * Yield significant at the.1 level, corn 15% moisture. + K Cherokee, IA * Hardin, IA * * Yield significant at the.1 level, corn 15.5% moisture. STK - Depth + K 17 K increased yield on soils STK > 5 ppm K increased yield on soils STK > 5 ppm Miller, 1 Miller, 13 Corn Yield vs STK by Depth Corn Ear Leaf N:K vs Yield KRx Yield 5 sites vs soil test K by depth, IA sites Treatment/ Site NEL 1 NIE 9 LAR FRI 15 CAL 3 K bu/ac K 1 bu/ac Delta Yield Depth (in) STK (ppm) Yield increase to application of 5 lbs/ac K at V-V. * Grain responsive sites Miller, 13 Contrast five KRx 1 sites with highest and lowest N:K ratios, show substantial yield differences. High N:K Ratio Site STK N:K 1 Yield 3 ppm Ratio bu/ac NEL NEL NIE BLA FRI Average stdev Low N:K Ratio Site STK N:K Yield 1 N:K ratios based on corn ear leaf at VT-R1 growth stage. STK based on - sample V3 growth stage. 3 Yield based on average of replications, lb/ac K rate plots, KRx. ppm Ratio bu/ac LAR CAL BEC CAL CAL Average stdev.15 1 Difference 59 bu/ac Miller, 13 Corn Ear Leaf N:K vs Yield Corn Yield vs STMg by Depth Contrast five K RX 1 sites with highest and lowest N:K ratios, show substantial yield differences. High N:K Ratio Site N:K 1 Mg:N Yield Ratio Ratio bu/ac NEL NEL NIE BLA FRI Average stdev Low N:K Ratio Site N:K Mg:N Yield 1 N:K ratios based on corn ear leaf at VT-R1 growth stage. Yield based on average of replications, lb/ac K rate plots, Krx. 3 Elwali et al 195, critical earl leaf VT Mg:N value is.7±.7. Ratio Ratio bu/ac LAR CAL BEC CAL CAL Average stdev Difference 59 bu/ac Miller, 13 KRx Yield 5 sites vs soil test Mg by depth, IA sites Treatment/ Site BEC7 NIE 9 MYC1 BLA1 CAL 3 K bu/ac K bu/ac Delta Yield Depth (in) STMg (ppm) Yield increase to application of 5 lbs/ac K at V-V. * Grain responsive sites Miller, 13 1

17 Mg lbs/ac /1/1 Summary Continued Soils? Tissue analysis? Additional yield data for 13 is being compiled from IN, IL, IA and NE locations. Increasing corn population and yield levels have increased nutrient uptake from a decreasing soil volume per plant. Nutrient accumulation for corn follows a defined proportional ratios as a function of heat units (GDD). During vegetative growth K accumulation (lbs/day) proceeds N and rates of both decrease by stage R1. During grain fill N, P, S and Mg continue to accumulate in the grain where as K and Ca do not. Diffusion is the principal mechanism providing soil P, and K. Temperature and moisture have major impact on root growth uptake and diffusion. Additional yield data for 13 is being compiled from IN and IA locations. Assessing leaf tissue concentrations based on lab analysis uncertainty, shows significant K relationships for N:K ratio across 3 years, and elevated by drought (1). Decrease leaf K was highly correlated with increased leaf Mg and Ca, and increases with Mg:N and Ca:N ratios. Results support those of Elwali et al 19, DRIS Norms. Results of K trials across the corn belt show K response on soils with 1-9 ppm STK. Significant K stratification by depth was noted. Sites with the highest N:K and Mg:N ratios show consistent lower grain yields. With K deficiency, due to low STK or soil moisture stress, ear leaf tissues show elevated Mg and suboptimal yields. Miller and Bower, 13 Miller, 13 Corn Mg Accumulation Removal is 5% of total uptake Ear + Shank Stem Upper Leaves Lower Leaves GDU 1 Calculated from: Karlen, Flannery, and Sadler. 19. Agron J. :3-. Miller, 13 Corn Population vs K Rate At sites K was applied at two rates to four corn populations. Results for CAL site, Cherokee IA, soil test K level: 171 ppm. Population K Rate 5 K Rate 1 Plts/ac bu/ac bu/ac, , 1 3, 1, K application of 5 lbs/ac K at V-V. Harvest corn populations:,; 9,1; 3, and, plts/ac KR X Corn Yield Response KRx Project Yield Results 1 six Illinois, Indiana and Nebraska sites. Site STK Check +K Increase Cty / State lbs/ac bu/ac Merrick, NE Vermillion, IL Livingston, IL 9-1 Piatt, IL * Sullivan, IN Warsaw, IN * Yield significant at the.1 level, corn 15.5% moisture. STK - Depth K increased yield on a soil STK > 3 lbs/ac K effect on ear size Check 13 + K 1 Miller, 13 Miller, 13 17

18 Corn Yield bu/ac /1/1 Ear Leaf Data Analysis 9 years of Corn Trends Review Nutrient Sufficiency Levels Apply Laboratory Precision to Data Assess Nutrient Ratios Elwali et al, 195 Assessing Leaf Nutrient Levels Indiana / Iowa corn ear leaf data (VT), based on published diagnostic norms, have significant nutrient deficiencies for K, Mg, and to small extent N. Filtering leaf tissue concentrations based on lab analysis uncertainty, shows significant K relationships for N:K, Mg:K and Ca:K. Decrease leaf K was highly correlated with increased leaf Mg and Ca, with little change in N, P or S. K deficiency threshold.1%. Increased corn populations and yield have resulted in greater grain K removal and increased soil K removal per plant,. times increase since 19 Year Population Root volume per Plant ft 3 Yield Bu/ac K Removal mg / plant K Plant Removal mg per L of soil Root volume calculated from population, adjusted for row width change 19, based on 3 ft depth K removal calculated based on grain yield x.5% K per bu. K removal per L of soil based on population Miller, 13 N:K ratios are relatively constant across two regions and years. These are only observations, and data is limited to support the effect of these ratios on Miller, 13 K Soil Testing The Next Generation K RX Soil K Test The current index approach to soil test K is to treat the soil as a barrel. It s a matter of how full (low, medium or high) the soil barrel is as to whether we apply K fertilizer. This approach ignores what is the rate of flow of K out of the barrel into the growing plant. Rate is the limiting factor. Analogy, a tractor s power its not about how big the tractor engine is, its about where the throttle is positioned. Soil K+ Mg++ Ca++ The method is based on measuring the rate of K release from the soil using intact plant roots. Focus is to measure the supply rate, not the quantity available. Preliminary results show diffusive release rates mg/kg/day. Work is in progress on the K RX soil test. Additional studies on crop population and application timing. Miller, 1 Miller, 1 Miller, 1 Miller, 1 Soil Testing - Then and Now Iowa Corn Yields Parameter Tillage Corn Genetics Intensive tillage: plow, disc etc. Hybrids were new Populations, 1, plts/ac Yields IL Ave 3 bu/ac IA - Ave 3 bu/ac MN - Ave 3 bu/ac yields based on 5 year average, 11 state average Tillage Reduced Min till and No Till Multi-stacked hybrids corn, specific traits, 3, plts/ac Variable rate pop. IL - Ave 157 bu/ac IA - Ave 17 bu/ac MN Ave 15 bu/ac Row width has narrowed and corn populations increased from 1, in 193 Miller, 1 to, by 19. Today populations pu Agronomic advancements have pushed yield 3 times in the past 1 years. Soil testing facilitated yield increases and again Yield Increase bu/ac/yr 5 yr ave Year Source: National Agricultural Statistics Database, Years 195-1, Miller, 1 1

19 GDD F Deviation K lbs / Ac /1/1 Corn K Uptake Impacted by: - Temperature - Moisture - Root Zone K Availability /3 /9 /19 /9 5/9 5/19 5/9 / /1 / Mon/Day Iowa: May daily high temps were.5 F warmer than 1 yr ave, resulting in an added 153 GDD F. June was 13 GDD F. Thus V - V1 growth advanced faster and peak K uptake period shortened. Decreased soil moisture V-V1 reduced soil K mass flow, and roots grew in deeper in the profile, where K is less available. Thus K deficiency symptoms were more common. Soil Potassium Dynamics Robert O. Miller Colorado State University Fort Collins, CO Ellsworth Iowa July 1 1 GDD based on daily temperature Webster City, March-July 1 Miller, 1 Miller, 1 Soil Potassium Fractions Potassium Aerial Accumulation Wheat - California Total Soil K -, ppm? Nonexchangeable K 1 ppm Grain Head Stem Leaves K: 1 lbs/ac/day Yield 1 bu/ac 1% 13% 53% Miller, Exchangeable K - ppm Soil Solution K - ppm 5 % Miller, 199 GDU *above ground Corn Growth: Sayre - 19 Soybean K uptake Where the soil roots are.. Amount of soil K depletion by depth and distance from the Row at VT. Verify root activity using tetraozolium staining. Verify effect of plant population on K uptake and soil K depletion with depth. The N accumulation rate was maximum at VT-R1, at a rate of. lbs/ac/day. The K accumulation rate was maximum at days at a rate of 3. lbs/ac/day, lasting for 1 days. Peak K rate proceeded peak N uptake by 1 days, and decreased to near zero at days. 1 Calculated from Sayre, 19, Plant Phys Days After Emergence Dry Matter N K lbs/ac/day Miller, 13 19

20 GDD (F) Delta Yield bu/ac Samples /1/1 Impact of GDD on Corn Development 1 Corn: Yield: Max K Uptake Rate Impact of GDD impact Corn Development 35 3 per. Mov. Avg. 1 5 (1) 5 per. 1 Mov. Avg. 5 (1) Mon/Day GDU GDU 1-Apr -Jul 3-Jul 11-Apr 1-Apr 1-May 11-May 1-May 31-May 1-Jun -Jun 3-Jun 1-Jul Month Date Apr Champaign, Illinois Weather station, 5 day averge. May May Source / Year Population Yield Total K Rate Max K uptake Rate plants/ac bu/ac lbs/ac lbs/ac/day Sayre, 19 1, Chandler, Hanway, 19 17, Ottman and Welch, Karlen et al, 19, Bender et al, , Note, soil test K was 153 ppm, there was no reported use of K fertilizers. Miller, 13 Miller, 13 Mechanisms of Root Nutrient Uptake Lab Soil Test K - Iowa The mechanisms of nutrient uptake are: mass flow; root interception and diffusion. K+ Root Interception accounts for < % of K uptake Mass Flow accounts for < 1 % of cation uptake Observations Soil Test K ppm Distribution 1 Soil Test K Mean 13 ppm K ppm 7 9 < < All Samples < Mg ++ Diffusion accounts for > % of K nutrient supply 1 Mean STK Dropping -7 ppm/year Ca ++ Soil diffusion distances for potassium are cm to the plant root. Diffusion Is the Major Mechanism for K Soil K Level ppm K Miller, 1 Miller, 13 1 Source: LGI Laboratories, 1. Miller, 11 Lab Soil Test K - Indiana Observations South 3 South Count K %. lbs/ac % < 3 lbs/ac < 3. 7.% < lbs/ac 1.3% < 1 lbs/ac < 7. < M-3-K (lbs/ac) Source: Sure-Tech Laboratories Count % < K 3 lbs/ac % lbs/ac 33.% < lbs/ac < 3 1.% < 1 lbs/ac73. < < 1 1. Median STK values dropped ppm M-3-K (lbs/ac) Miller, 11 KR X Corn Yield vs STK years A K application 1 of 5 lbs/ac improved grain yield at 3 nine of forty-eight locations * Significant Increase Drought sites yield < 1 bu/ac Soil Test K -" (ppm) 1 Yield increase to application of 5 lbs/ac K at V-V. Probability of yield response STK 75 to 15-5% STK 15 to - 5% STK to 3-3% STK 3 to - % Ave yield increase 11 bu/ac Miller, 13

21 Grain Yield Bu/ac K lbs/ac/day Exchangeable K (ppm) /1/1 Impact of K Diffusion on Oat Mg Uptake and yield 9 Years of Corn Trends Grain Yield vs Root Volume 1 Grimme, L.C., von Braunschweig, K. Nemeth. 197/75. K, Mg and Ca interactions as related to cation uptake and yield. Buntehof Abs. :7-. From Handbook of Plant Nutrition, Barker and Pilbeam Grain Yield (Iowa) Root Volume per Plant Thus yield increases 1 have been counter to decreases in rooting volume per plant Year 1 Corn yield 5 yr weighted average, source: Iowa Root volume per plant calculated, adjusted for row width change, based on 3 ft depth 5 3 Root Volume per Plant (ft 3 ) Miller, 13 K RX Experiment K was applied at corn growth stage V-V using spoke wheel injector at rates of, 5 or 1 lbs K per acre. Plots were 15 ft x 3 ft, eight replications. STK sampled at planting, corn ear Leaves were sampled at VT, and grain yield and moisture determined based on 3/1 th acre of each plot at black layer. University of Illinois Publication Khan and Mulvaney see no value in soil testing for exchangeable K and instead recommend that producers periodically carry out their own strip trials. University of Illinois, October, 13 AgProfessional.com/News Year of Biweekly sampling Miller, 13 Miller, 1 Corn Yield: Max K Uptake Rate 13 3 Nutrient Uptake and Root Density - Source / Year Population Yield Total K Uptake Max K Uptake Rate plants/ac bu/ac lbs/ac lbs/ac/day Sayre, 19 1, Chandler, Hanway, 19 17, Ottman and Welch, Karlen et al. 19, At days (5 GDD) K accumulation was max at. lbs/ac/day and root density was 1.5 cm/cm 3 for the -1 depth. Bender et al, , Note, soil test K was 153 ppm, there was no reported use of K fertilizers. High Mg uptake noted. Miller, 13 At 7 days (7 GDD) K accumulation was maximum at 13. lbs/ac/day and root density was 3.5 cm/cm 3 for the -1 depth,. cm/cm 3 for Estimated from Karlen et al 19, and Mengel and Barber 197. Miller, 13 1

22 Percent of Samples Leaf Mg Leaf K Leaf N Leaf K Growth as Percent of Maximum /1/1 STK Changes in a Field.5 N vs K. K vs N Location: North Central Iowa 1 Average STK drop: 55 ppm Decrease 13-1 ppm/yr y = -.1x + 1.9x R² = Leaf N. y =.11x R² = Leaf K.7..5 K vs Mg 3 Mg vs K y = -.95x x x R² = Leaf K y = 1.955x x x R² = Leaf Mg 1 Source, Midwest Independent Samplers, 5 grid points. Fertilizer Application lbs/ac Miller, 1 Lab Soil Test K: IA and MN Nutrient Critical Values Observations Soil Test K Mean 1 ppm STK (ppm) STK ppm < < < Ave % of samples have K Rec What Does Plant Analysis Show Deficiency 1% Reduction in Growth Concentration below which yield is Marginal Adequate Transition zone (symptoms or no symptoms) Deficient zone (symptoms) High Critical Concentration Defined by Experimentation Concentration of Nutrient in Tissue (dry basis) Toxic Tissue Analysis provides confirmation on nutrient management effectiveness 1 Source: MVTL Iowa, Mehlich 3 K Miller, 15 compromised and/or deficiency symptoms observed Modified from Reuter and Robinson, Miller, 13 Corn Ear Leaf Nutrients Observations Western Indiana: GS VT-R1, Number of samples 9 51/yr Analysis Critical Level 1 Percent (%) of Samples Deficient N (%) < P (%) < K (%) < Mg (%) < Ca (%) < Deficiency Most Frequent: K Field grid results show downward shifts in STK over years in north central Iowa. A survey of MVTL STK results show % soils are likely K responsive (ISU Recommendation). Ear Leaf results show K the most deficient among essential nutrients, 5-3%. What has changed? Robert Nielsen, 9, Purdue University _35555_3173_n.jpg Source: Betsy Bower, Ceres Solutions Miller, Bower, & Smith, 15 Miller and Bower, 15

23 Corn Popualtion Grain K Removal (lb/ac/yr) Corn Popualtion /1/1 9 Years of Change 9 Years of Corn Trends Population vs Grain Yield Populations have increased from, in 19s to 3, plts/ac, today. Tillage, Reduced and No-till systems now dominate production. Nitrogen applications rates have increased with population and yield potential. Planting date has advanced from late May to mid April, + 5 weeks. Corn hybrid genetics continue to increase yield potential and improve pest resistance Population Grain Yield (Iowa) 5 yr weighted Ave Year Grain Yield (bu/ac) Increases in yield have paralleled increases in plant population 1 Corn yield 5 yr weighted average, source: Iowa Populations estimates based on university guides and research experiments Miller, 15 Miller, 15 9 Years of Corn Trends Population vs Root Volume 9 Years of Corn Trends K Removal vs Root Volume Population Root Volume per Plant 1 Increases in plant 1 populations 5 results in decreases in the rooting volume per plant Year 1 Population estimates based on university guides and research experiments Root volume per plant calculated, adjusted for row width change, based on 3 ft depth 35 plts/yr 5 3 Root Volume per Plant (ft 3 ) Miller, Grain K Removal (Iowa) Root Volume per Plant. lbs/ac/yr 1 Increased grain K removal 5 17 lbs of K removed in 5 Years 1 coincides with decreased rooting volume per plant Year 1 Calculated K removal based on grain yield x.5% K per bu, IPNI (note prior to 197 K removal higher, with ear harvest) Root volume per plant calculated based on population, adjusted for row width change 19, based on 3 ft depth 5 3 Root Volume per Plant (ft 3 ) Miller, 15 Decreasing Plant Root Volume Nutrient Deficiency Threshold 1 Percent of Samples Deficient < Less Than N (%) < P (%) < K (%) < Mg (%) < Ca (%) < S (%) < Zn (ppm) < Population and K Removal Increasing plant population has resulted in a 5% decrease in root volume per plant over 5 years in the Midwest. Increase yields, have increased K removal in the grain. Combined effect of population and grain K removal, has resulted in a % increase in soil K removal from the root zone of each plant. 19 root soil volume per plant 1, plts/ac 15 root soil volume per plant 3, plts/ac Miller, 15 3

24 Soil Depth (in) /1/1 Tillage and Soil K Stratification Corn Tissue Research Plowed Field No-Till Field STK 1 3 Decrease tillage systems show increased K stratification. Subsoil K is depleted in reduced till fields. Corn ear leaf nutrients at growth stage VT represent a synopsis of plant nutrition at the end of the vegetative stage. Ceres Solutions, surveyed corn leaf tissue nutrients at 3 growth stages in 1, expanded in in IN and IA Robert Nielsen, 9, Purdue University _35555_3173_n.jpg Urbanowicz, 15 Miller and Bower, 13