Variability in Tissue Testing What Does It Mean For Nutrient Recommendations?

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1 Variability in Tissue Testing What Does It Mean For Nutrient Recommendations? Daniel Kaiser Assistant Professor Department of Soil, Water and Climate U of M Twin Cities dekaiser@umn.edu

2 Why Take a Plant Sample It s fun, and I have nothing better to do! Diagnose a nutrient deficiency within a field Sample the good, the bad, the ugly Monitor the nutrient status of high yield crops Some dangers in interpretation of results Need to follow strict protocols

3 History of Tissue Testing Some of the early methods date back to the 1940 s Gained traction as the analytical procedures developed more rapid testing Multi-element analysis with an ICP Problems with use still persist that were encountered 60 + years ago

4 Limitations on the Use of Plant Tissue Tests Reliability of interpretive data Utilization of ratio and balance concepts Hybrid/Varietal influences Changing physiological processes that occur at varying elemental concentrations Source: 1959 Plant Analysis and Fertilizer Problems Colloquium --Cited from Jones Jr., 2012

5 Values for Making Interpretations Critical value Tissue concentration value at 90% of maximum yield Standard value General mean for crops normal in appearance under well-managed conditions Sufficiency range Range between deficiency and toxicity --Cited from Jones Jr., 2012

6 Time of Sampling Predictability gets better later in the season Sampling is more difficult Corrective measures are more challenging Environmental factors affect early growth For example early starter effects from band applications can promote uptake Plant demand is very low for all nutrients early in the growing season

7 Illinois Data Published in Agronomy Journal Bender, Haeglele, Ruffo, and Below Uptake of transgenic hybrids 6 hybrids

8 Plant Parts to Collect Best: Corn Ear leaf at R2 Soybean upper most fully developed leaf at mid-bloom (check with lab about petiole) Early season whole plant above ground for corn Whole plant soybean data is less beneficial Some potential for taking fully most developed corn leaf at V10

9 207 bu/ac 130 bu/ac 232 bu/ac

10 Low YLD High YLD V. High YLD N (%) P (%) K (%) Ca (%) < 0.01 < 0.01 < 0.01 Mg (%) S (%) B (ppm) Fe (ppm) Mn (ppm) Cu (ppm) Zn (ppm)

11 Relative Corn Yield (% of Maximum) n=485 Deficient Excessive When Ear Leaf N < 2.47 RelYLD= (Leaf P) (Leaf N) Ear Leaf N Concentration (%) at R2 R 2 =0.48 P<0.001

12 Ear Leaf Nitrogen Ear Leaf Phosphorus Relative Corn Yield (% of Maximum) Relative Corn Yield (% of Maximum) n= When Ear Leaf N < 2.47 RelYLD= (Leaf P) (Leaf N) 2 R 2 =0.48 P< Ear Leaf N Concentration (%) at R2 Ear Leaf Potassium n= When Ear Leaf K < 1.43 RelYLD= (Leaf K) (Leaf K) 2 R 2 =0.13 P< Ear Leaf K Concentration (%) at R2 Relative Corn Yield (% of Maximum) Relative Corn Yield (% of Maximum) When Ear Leaf P < 0.38 RelYLD= (Leaf P) (Leaf P) 2 R 2 =0.45 P< Ear Leaf Sulfur n=385 Ear Leaf P Concentration (%) at R Ear Leaf S Concentration (%) R2=0.40

13 Sufficiency Ranges Calculated Response Trial Data Crop Stage Nutrient Low High Plant Analysis Handbook Corn R2 N V5 P* R2 P V5 K* R2 K* R2 S Soybean V5 P* na na R2 P* V5 K* na na R2 K* R2 S *Analysis indicated that a model was significant but R 2 was less than 0.20

14 Soybean Trifoliate P at R2 Relative Soybean Yield (% of Maximum) n=99 20 When Tri P < 0.45 RelYLD= (Tri P) (Tri P) 2 R 2 =0.32 P< Trifoliate P Concentration (%) at R2 R 2 =0.47 Data shows two sets of response Similar data for K exists Do critical levels differ by site or some other factor

15 Early Season Sampling Luxury consumption of nutrients can make identifying critical levels in early season samples difficult Taking comparative samples may have greater benefit than fishing for problems Sample multiple field areas of the same hybrid, planting date, management

16 Relative Corn Grain Yield (%) Relative Corn Grain Yield (%) Phosphorus and Potassium Example Early Plant Concentration Long Term P Study Locations (Lamberton & Morris) Long Term K Study Locations (Delavan & Morris) V5 Phosphorus Concentration (%) V5 Potassium Concentration (%) R 2 =0.14 Critical level 0.39% R 2 =0.15 Critical level 2.99%

17 Corn V5 %P Soybean V5 %P Relative Corn Yield (% of Maximum) n= When Plant P < 0.38 RelYLD= (%P) (%P) 2 R 2 =0.03 P< Whole Plant P Concentration (%) at V5 Corn V5 %K Soybean V5 %K Relative Soybean Yield (% of Maximum) n= When Plant P < 0.23 RelYLD= (%P) (%P) 2 R 2 =0.08 P< Whole Plant P Concentration (%) at V5 Relative Corn Yield (% of Maximum) n=1051 When Plant K < 3.06 RelYLD= (%K) (%K) 2 R 2 =0.03 P< Whole Plant K Concentration (%) at V5 Relative Soybean Yield (% of Maximum) n=1124 When Plant K < 3.12 RelYLD= (%K) (%K) Whole Plant K Concentration (%) at V5 R 2 =0.03 P<0.001

18 Consider Effects Early in the Growing Season Cool wet soils can limit uptake of nutrients My not affect concentration if plant growth is proportional to nutrient uptake Starter fertilizer can increase plant mass Will this result in dilution of nutrients Small plants can sometimes result in an accumulation of nutrients in the plant Accumulation/dilution of elements in the plant

19 Other Items of Note Most information given in guidelines is centered around the Plant Analysis Handbook II (Mills and Jones) Data is claimed to be sufficiency based on yield response Values have not changed through several iterations of this text Is this a robust dataset? Response to some micros is not that common How large of a dataset was used and where does it come from?

20 Jones Jr Identifies an upper and lower limit to critical values Essentially the sufficiency range Growers can establish their own standard values He mentions this should not be done for annual crops Over time, a sufficiency range could be established out of standard values

21 Standard Values vs. Sufficiency Calculated* Mills and Jones Sufficiency Nutrient Low High Low High N P K Ca Mg S B Cu Mn Zn *Calculated values from soybean micronutrient studies , Yield did not differ at any location

22 Standard Values May resemble sufficiency ranges No backing yield data If there is no yield data to back up the values do they have any meaning? How much data is based on standard values and not sufficiency guidelines?

23 Sampling Issues Two studies with Corn and Spring wheat have demonstrated a strong link between tissue variability and environmental stress A significant portion of variation could be explained by temp. and precip. Factors Additional variation could be attributed to the growth stage of a crop at sampling Sampling at the correct time is impoportant.

24 How Much do Hybrids Vary? Ear Leaf Potassium Ear Leaf Zinc R2 Ear Leaf K Concentration (%) Potassium - 12 Site Average a a d d DKC53-78 DS9303SS DS9501SS P0062XR c P0193AM1 b P9917AM1 R2 Ear Leaf Zn Concentration (ppm) Zinc - 12 Site Average a b bc DKC53-78 DS9303SS DS9501SS c P0062XR P0193AM1 a bc P9917AM1 Red line represents the lower end of the sufficiency range defined by Mills and Jones

25 Hybrid Differences Southern MN locations Hybrid Yield N P K B Zn bu/ac % ppm DKC b 2.99b 0.33a 1.74a 7.4a 19.7a DS9303SSX 199bc 2.93bc 0.28c 1.48d 7.3a 18.2b DS9501SSX 193c 2.88c 0.30b 1.46d 6.1c 17.5bc P0062XR 201b 2.72d 0.29c 1.69a 5.7d 17.3c P0193AM1 211a 3.06a 0.27d 1.54c 6.7b 17.5bc P9917AM1 200bc 2.89c 0.30b 1.60b 6.0c 19.5a Disconnect between yield and tissue concentration for all elements Would we expect differences in yield among hybrids to be directly related to differences in concentration of elements?

26 Soybean Trifoliate Samples N P K Zn Mn B Very Low STP Taken early morning Very Low STP Taken mid afternoon Very High STP Taken early morning Very High STP Taken mid afternoon

27 Sample Variability Sampling Nitrogen Zinc 9am 12pm 4pm 9am 12pm 4pm Soybean Trifoliate Corn Upper Leaf Corn Ear Leaf

28 Where do you take a Sample N P K Zn Mn B Top of Plant Middle of Plant Bottom of Plant

29 Grid Plant Sample Example 2 corn and 2 soybean locations Sampled fields grid soil sampled 1 exception SB field near Northfield Samples all collected around V5 Fields were harvested with combine equipped with a yield monitor Following example is for corn and soybean fields near Stewart, MN

30 Potassium in Plants at V5 (%) Data collected on 2.5 acre grids

31 Correlation with Yield N P K Ca Mg S B Fe Mn Cu Corn SB Correlations between and 0.30 are generally not significant enough to be concerned about Greatest positive correlation with final yield was K for corn and Ca for soybean No real predictive power of individual nutrients on corn or soybean yield

32 Keys to Good Plant Sampling 1. Define why you are taking a sample 2. Sample a plant at a time that provides accurate diagnostic information 3. Sample the correct plant part 4. Take an adequate number of samples to ensure a good sample 5. Do not read too much into the results

33 Boron Toxicity in Soybeans 5 lb/ac B broadcast preplant Sandy soil Dry spring

34 My Parting Thoughts Plant analysis has become and excellent sales tool The system as a whole is a black box Information provided is only as good as the data behind it Values are easily adjusted Most low values are a direct result of plants responding to adverse environmental conditions Examples: boron, zinc, and potassium

35 None of the various interpretative procedures discussed is infallible, and the techniques are best used by the most experienced. The interpretation of plant analysis is still an art in which the interpreter must use all of the resources available, including a soil test result, to determine the nutrient element status of the plant in order to advise on treatments to correct hidden hunger ---Source Mills and Jones 1996 Plant Analysis Handbook

36 Thank You Questions? Daniel Kaiser University of Minnesota