Assessing Potassium Needs

Transcription

1 Assessing Potassium Needs Robert O. Miller, Colorado State University, Fort Collins, CO

2 My Background 5 th Generation farm family in eastern Nebraska 500 acres corn and soybeans Affiliate Professor Colorado State University. - Ph.D. Montana State University, - Extension Soil Specialist UC Davis. Conduct Regional Research in Soil Sampling, Soil Fertility, Lab Analysis and Coordinate the Agricultural Laboratory Proficiency (ALP) Program. Miller, 2010

3 Knowledge What we don t know, we don t know What What we we know know What e we Know What we Know Over time the circle of knowledge grows, as does what we know we don t know What we know we don t know 4

4 Outline Potassium Perspective: Observations Overview of changes in agronomic practices Corn Growth and Development: Impact of on nutrient accumulation Potassium Corn Response: Results of K research in the Midwest Moving Forward: K fertility approaches

5 STK Changes North America Source: IPNI, 2010 Better Crops with Plant Food p :4

6 STK Changes in a Field Location: North Central Iowa 1 Average STK drop: 55 ppm Decrease ppm/yr Fertilizer Application 220 lbs/ac 1 Source, Midwest Independent Samplers, 58 grid points. Miller, 2014

7 Percent of Samples Lab Soil Test K: IA and MN Observations Soil Test K Mean 142 ppm STK ppm < < < Ave 72% of samples have K Rec STK (ppm) What Does Plant Analysis Show 1 Source: MVTL Iowa, Mehlich 3 K

8 Corn Ear Leaf Nutrients Western Indiana: GS VT-R1, Number of samples /yr Analysis Critical Level 1 Percent (%) of Samples Deficient N (%) < P (%) < K (%) < Mg (%) < Ca (%) < Deficiency Most Frequent: K Source: Betsy Bower, Ceres Solutions Miller, Bower, & Smith, 2015

9 Corn Ear Leaf Nutrients 2012 Growth Stage VT-R1 Analysis Critical Level 1 Percent Deficient (%) Iowa 2 Nebraska 3 Minnesota N (%) < P (%) < K (%) < Mg (%) < Ca (%) < S (%) < Zn (%) < Deficiency Most Frequent: K source Iowa survey Midwest Independent Soil Samplers, 321 fields 3 source: Nebraska survey 650 fields, Minnesota, survey 420 fields Miller, Bower, & Smith, 2015

10 Observations Field grid results show downward shifts in STK over years in north central Iowa. A survey of MVTL STK results show 64% soils are likely K responsive (ISU Recommendation). Ear Leaf results show K the most deficient among essential nutrients, 25-30%. What has changed? Robert Nielsen, 2009, Purdue University _355055_ _n.jpg Miller and Bower, 2015

11 90 Years of Change Populations have increased from 8,000 in 1920s to 32,000 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.

12 Corn Popualtion 90 Years of Corn Trends Population vs Grain Yield Population Grain Yield (Iowa) 5 yr weighted Ave Year Grain Yield (bu/ac) Increases 40 in yield have paralleled increases in 20 plant population 1 Corn yield 5 yr weighted average, source: Iowa 2 Populations estimates based on university guides and research experiments

13 Corn Popualtion 90 Years of Corn Trends Population vs Root Volume Population Root Volume per Plant Year 350 plts/yr Root Volume per Plant (ft 3 ) Increases in plant 1 populations results in decreases in the rooting volume per plant 1 Population estimates based on university guides and research experiments 2 Root volume per plant calculated, adjusted for row width change, based on 3 ft depth

14 Grain K Removal (lb/ac/yr) 90 Years of Corn Trends K Removal vs Root Volume Grain K Removal (Iowa) Root Volume per Plant 0.4 lbs/ac/yr Root Volume per Plant (ft 3 ) lbs of K removed in 50 Years Year Increased grain K removal 1 coincides with decreased rooting volume per plant 1 Calculated K removal based on grain yield x 0.225% K per bu, IPNI (note prior to 1970 K removal higher, with ear harvest) 2 Root volume per plant calculated based on population, adjusted for row width change 1960, based on 3 ft depth 0

15 Decreasing Plant Root Volume Population and K Removal Increasing plant population has resulted in a 50% decrease in root volume per plant over 50 years in the Midwest root soil volume per plant 16,000 plts/ac 2015 root soil volume per plant 32,000 plts/ac Increase yields, have increased K removal in the grain. Combined effect of population and grain K removal, has resulted in a 240% increase in soil K removal from the root zone of each plant.

16 Soil Depth (in) Tillage and Soil K Stratification Plowed Field No-Till Field STK Decrease tillage systems show increased K stratification Subsoil is depleted in K in reduced till fields. Urbanowicz, 2015

17 Nutrient Uptake 200 bu/ac Grain P Removal lbs/ac K Removal lbs/ac Crop Stover Residue P K Ca Mg lbs/ac/yr yrs With decreased tillage stratification will increase over time 1 Source IPNI 2012.

18 K lbs/ac Potassium Accumulation: Karlen et. al Corn Yield: 308 bu/ac 20% % *above ground 14% 15% GDD 1 Calculated from: Karlen, Flannery, and Sadler Agron J. 80:

19 K lbs/ac/day Corn Potassium Accumulation Rate K Uptake Peaks Yield bu/ac K lbs/ac/day *above ground -2 Days After Planting V4 V8 V12 VT R1 R2 1 Calculated from: Karlen, Flannery, and Sadler Agron J. 80:

20 Summary K Fertility 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! Robert Nielsen, 2009, Purdue University _355055_ _n.jpg Miller and Bower, 2015

21 K Research Project KRx project was launched in 2011 to evaluate grain yield response to applied K across 6 states, 76 sites over four years. Assess STK, ear leaf nutrient and K fertilizer on grain yield. K Deficiency Winchester, Indiana, Dave Taylor Miller, Bower, Smith, 2015

22 K RX Corn Research a study was conducted across 76 sites in six states to evaluate response to K. K was applied at 0, 50, 100 lbs/ac at growth stage V3 V5, ranging 18,600 42,400 plts/ac, eight replications. STK sampled at planting, corn ear leaves were sampled at VT, and grain yield and moisture determined based on 3/1000th acre of each plot at black layer. 4Rs of Fertility Time Place Material Rate Robert Nielsen, _355055_ _n.jpg

23 Depth (in) STK Stratification Five Sites STK (ppm) CAL23 NH1 GIB FRI15 SMI STK shows consistent elevated surface levels (> 3x subsoil) across 15 of 16 sites in 2014, 78% of all sites over four years. Specific sites (i.e. GIB) the 0-2 depth is 5X the content of the 6-8 depth. All sub soils had STK < 90 ppm KRx sites: Iowa and Illinois.

24 KR X Corn Yield Response Krx Project Yield Results 2011 Six Iowa and Nebraska sites. K effect on ear size Site STK Check +K Increase Cty / State ppm bu/ac Cherokee, IA * Check 216 Calhoun, IA * Webster, IA Webster, IA * O Brien, IA Hamilton, NE * Yield significant at the 0.10 level, corn 15% moisture. + K 226 K increased yield on soils STK > 250 ppm

25 KR X Corn Yield Response Krx Project Yield Results 2012 Six Iowa sites Site STK Check +K Increase Cty / State ppm bu/ac Pocahontas, IA Palo Alto, IA * K effect on ear size Check 139 Calhoun, IA Wright, IA * Cherokee, IA * Hardin, IA * * Yield significant at the 0.10 level, corn 15.5% moisture. STK 0-6 Depth + K 167 K increased yield on soils STK > 250 ppm

26 Delta Yield bu/ac KR X STK vs Corn Yield - 3 years A K application 1 improved grain yield at 28 of 60 locations Probability of yield response STK 75 to % STK 150 to % STK 200 to % STK 300 to 600-8% Ave yield increase 11 bu/ac * Significant Increase Drought sites yield < 140 bu/ac STK 0-6" (ppm) 1 Yield increase to application of 50 lbs/ac K at V3-V5.

27 STK Dry vs Moist Yield Results 2014 Contrast comparison of soil STK of five lowest sites and five and highest sites, 2014 KRx research locations. Test Parameter Low Range STK Dry STK Moist High Range Delta STK 0-6 (ppm) Yield (bu/ac) K Response (bu/ac) STK 0-6 (ppm) Yield (bu/ac) K Response (bu/ac) Data: 2014 sixteen locations sorted by STK value, yield based control plots and response to K 50 lbs/ac.

28 Yield Response bu/ac K RX Ear Leaf K vs Yield A relationship between corn ear leaf K at VT and yield response to applied K, 43 sites % 16% Yield response to applied K Leaf K < 1.85%, 68 % responsive to K application Corn Ear Leaf K VT-R1 (%)

29 Leaf K Leaf N Ear Leaf Nutrient Ratios 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. 2.5 N vs K K vs N y = x x R² = Leaf N 2.0 y = x R² = Leaf K 1 Data: Corn Ear Leaf VT, Ceres Solutions 2013, 851 sites data grouped based on lab analysis uncertainty.

30 Leaf K Leaf Mg Ear Leaf Nutrient Ratios K vs Mg R² = Leaf K Mg vs K Survey data of corn ear leaves at VT-R1 from IN (851 sites) shows that with K deficiency (< 2%) there is a very significant exponential increase in leaf Mg. Sorting leaves by leaf Mg show a significant but small decrease in K. These results show strong evidence that there is a clear effect of leaf N content on K and that deficiency results in rapid Mg accumulation R² = Leaf Mg Does leaf nutrition reflect yield differences? 1 Data: Corn Ear Leaf VT, Ceres Solutions 2013, 851 sites data grouped based on lab analysis uncertainty.

31 Leaf Mg Corn Ear Leaf K vs Mg:K, Iowa 2012 Preliminary: Relation of leaf Mg:K ratio to based corn yield Site 1 N % K % Mg:K Yield bu/ac NIE NEL BEK THO CAL Replications per site y = x x x R² = Leaf K Requirement: N sufficiency must be met when assessing Mg:K ratio, need to include N:Mg Miller and Bower, 2015

32 Leaf Mg:K and N:Mg vs Yield 2012 Contrast five KRx sites with highest and lowest leaf Mg:K ratios, show substantial yield differences. 16 Sites Limited: Leaf N > 3.0 % (Range ) High Mg:K Ratio Site Mg:K 1 N:Mg 2 Yield 3 Ratio Ratio bu/ac GIB NEL NIE BLA NEL Average stdev 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 66 bu/ac 1 Mg:K ratios based on maize ear leaf at GS VT-R1 8 reps, three states 2 Elwali et al 1985, critical ear leaf GS VT Mg:K 0.10 ± 0.06; N:Mg value 14 ± Yield data KRx project, 0 lb/ac K plots, 8 replications. Miller, Bower, & Smith, 2015

33 Yield and Leaf Nutrient Ratios Cluster analysis 2 of KRx sites over four years shows yield differences for two primary clusters, sites < 1.85% K and N:Mg < 10 and sites with K > 1.85 %, N:Mg >10. N:Mg Ratio Yield Differences Year bu/ac Relationship consistent across years Data: Corn Ear Leaf VT K and N:Mg ratio, Corn yield data bases on control plot yield 8 replications. Miller, Bower, & Smith, 2015

34 KRx Conclusions Results show side dress K response at 46% of 76 research sites over four years in the Midwest. STK levels < 150 ppm are highly responsive, ppm moderately responsive (52%), ppm minimal responsive (37%) to side dress K. Additional Research is planned for 2015 in IN, IL IA and MN. 76 Midwest site years, grain yields are optimum when ear leaf K > 1.9%, ratios Mg:K < 0.15 and N:Mg ratios > 10. Sites outside these leaf ranges show significant limitations on yield. Miller Bower and Smith, 2015

35 Why STK Issues STK is estimate of K supply, based on probability of response Plant growth and therefore K uptake, is demand driven Demand is set by population and is growth stage specific depth 2-12 STK does not estimate soil K rate lbs/ac/day Limits on soil K diffusion/supply V5-V12, result in Mg substitution Impact Yield -2

36 DM Kg/ha/day K Nutrition Driving Factors Daily Growth Rate Vegetative Biomass Grain Biomass Population: greater density, increase K uptake, reduced soil volume per plant. Nitrogen: drives growth rate, and K demand STK Level: higher values improve uptake. Yield: higher yields increase K removal per yr Days After Emergence Tillage: reduced tillage increase K stratification. Temperature: higher temps, faster growth rate, greater daily demand. Law of Unintended Consequences

37 Recommendations Assess sub soil K levels (2-6 or 2-8 ). STK indicate possible response, < 100 ppm likely response. Assess at 10-20% of grid points. Plant Analysis. Ear leaf (VT-R1) K < 1.9%, Mg:K ratios > 0.16 and N:Mg ratios < 10 are indicative of K deficiencies. Track annually to assess K mgt effectiveness. 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 2-4 yrs. High corn population and yields (>35,000 plts/ac), push K uptake and reduce root volume/plant. Adjust fertility.

38 Grain yield Response to K If your not looking for it...you ll never find it! Mike Lindaman, Boone IA Miller, 2007 Jessica Hagy: 0/04/40-things-to-say-before-you-die/3/ R Miller, 2002

39 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. 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

40 Acknowledgements Craig Struve, MISS, IA Tom McGraw, MISS, IA retired Betsey Bower, Ceres Solutions, IN Jodi Jaynes, Sure-Tech Laboratories, IN Larry May, Lincoln, NE Tim Eyrich, Winfield Solutions, NE Mike Lindaman, Ag Source LGI Lab, IA Larry May, Lincoln, NE Ray Ward, Ward Laboratories, NE Don Meyers, Rock River Lab, WI

41 Thank you for your time and attention