90 elements are naturally occurring on planet Earth

1. 8 elements > 99% of the Earth’s crust K (2.1%) Mg (2.3%) Na (2.4%) Ca (4.2%) Fe (5.6%) 90 elements are naturally occurring on planet Earth Al (8.3%)

2. Elemental concentrations in soil vs. earth’s crust 0.001% 0.01% 0.1% 1% 10% 100% Plant essential elements are green Light green elements are exceptionally enriched in soil relative to crust soil crust Adapted from Essington (2003)

3. These are not the only elements found in plants! ~ 18 elements have been identified as essential for the growth of all plants Soil C O H N K Ca Mg P S Cl Fe Mn Zn B Cu Mo air & water macronutrients micronutrients 0.1% V Ni Needed by some plants Si Co Na

4. Essential element criteria Organisms cannot complete their life cycles without EE EE are not replaceable by other elements EE are proven to be necessary for specific physiological functions and/or Essential elements are all relatively light elements

5. Some elements (e.g. Se, I, As, Cr) have been identified as essential for animals but not for plants. Boronis the only element that has been identified as essential for plants but not for animals

6. Micronutrients are important components of enzymes What is an enzyme? Enzymes are biomolecules that lower the activation energy required for biochemical reactions

7. minerals Where are the nutrients in soil ? Soil solids contain nutrients organic matter

8. Soil water contains nutrients H20 H20 K+ - - Ca+2 H20 - H20 - Mg+2 - - Al+3 Humus - - H20 H20 H20 exchangeable ions soil solution H20 H20 H20 H20 Clay - H20 Na+ - + - H20 + - K+ SO4-2 Ca+2 H20 H20

9. What’s in the soil soup ?? Ca+2 Fe+3 DOM NO3- Ca+2 Mg+2 NO3- H2PO4- Ca+2 Cu+2 DOM K+ NO3- K+ Mg+2 Ca+2 Zn+2 DOM NO3- Mg+2 Fe+3 DOM Ca+2 SO4-2 Adapted from Brady and Weil (2002)

10. Re-seasoning the soup Highly buffered soils have a large reserve of nutrients that can resupply the soil water Highly buffered Amount of nutrient in the soil Poorly buffered crop removal Modified from Havlin et al. (1999)

11. Which forms of nutrients are available to plants ? “active” OM humus exchangeable solution weatherable minerals inner sphere

12. Clay mineral Fe Fe Fe Fe O O - - - P O O Inner sphere HPO4-2 anion Outer sphere Ca+2 cation Diffuse ions Adapted from Brady and Weil (2002)

13. Inorganic nutrient forms taken up by plants Co2+

14. Plants take up mostly inorganic forms of nutrients when inorganic forms of nutrients are readily available In some natural ecosystems (e.g., tundra), organic forms of nutrients are very important

15. Nutrient availability varies with pH

16. Micronutrient deficiencies frequently occur when naturally acid soils are over-limed http://www.fftc.agnet.org/library/image/bc51002p7.html Avoid over-liming !!

17. Understanding nutrient uptake H20 NO3- N, S, P Transpirational stream Root exudates activate soil microbes H20 Ca+2 Root growth + Diffusion K+ H2PO4-

18. Feed the soil vs. Feed the crop Both strategies are important ! Healthy roots need available nutrients ! Unhealthy roots use nutrients inefficiently… Acute root disease Chronic root malfunction

19. Small increases in OM can improve macro-aggregation Superior air/water relationships Healthier root growth and function

20. Aluminum toxicity Aluminum toxicity

21. Classic concept of yield response to nutrient availability …… Macronutrients tend to have a broad sufficiency range Micronutrients tend to have a narrow sufficiency range Crop yield Deficiency Symptoms Nutrient availability How can we assess the availability of nutrients in soil?

22. Goals of routine soil testing Rapid Cheap Predictive Widely applicable Very different from research analysis of soil

23. By themselves, extractable nutrient levels are not informative. Extractable nutrient levels provide an index of nutrient availability that can be interpreted using results from field experiments.

24. Illinois Agronomy Handbook

25. Crop response to soil test P in IL Critical level for corn and soybeans

26. Build and maintenance approach

27. On average, 9 lbs of fertilizer P2O5 are needed to raise soil test P levels by 1 lb/acre On average, 4 lbs of fertilizer K2O are needed to raise soil test K levels by 1 lb/acre

28. Meaningful interpretation of soil test results requires field calibration 100 % yield 50 % yield Soil test P concentration (ppm) http://www.ipm.iastate.edu/ipm/icm/2003/11-17-2003/mehlich3.gif

29. moisture temperature microbial activity Extractable nutrient levels are not directly related to most of the factors controlling nutrient availability during a growing season. rooting depth root health

31. http://www.extension.umn.edu/distribution/horticulture/components/M1190fig1.htmhttp://www.extension.umn.edu/distribution/horticulture/components/M1190fig1.htm Relatively immobile nutrients Relatively mobile nutrients

33. So what about Nitrogen? Nitrogen is an integral component of many essential plant compounds Amino acids Proteins Nucleic acids Chlorophyl 2.5 - 4% of plant dry matter enzymes

34. Relationship between optimal N rate and optimal corn yield in IL (72 site years) Only 13 out of 72 site-years in IL required more than 1 lb of N per bushel too high 96% of the time 1.2 : 1 line 1 : 1 line BOTTOM LINE There is no line that fits this data well Yield is a poor predictor of optimal N rate !! too high 82% of the time

35. Well-fertilized crops often obtain more than half of their N from SOM Where does the N come from ? Why more soil N? More productive soils normally supply more N from SOM Magdoff and Weil (2003)

36. Weather often regulates crop productivity more than nutrient input rates in high productivity systems http://www.fertilizer.org/ifa/publicat/PDF/2005_ag_frankfurt_lammel_slides.pdf

37. The on-going process of N shifting from one form to another is collectively called the N cycle Soil Microbial biomass Plant biomass Plant uptake

38. Why is nitrate such a slippery character ? • Nitrate is an anion • Nitrate compounds are very soluble • Nitrate is next in line as an electron acceptor • when O2 is not present

39. Denitrification NO3-     NO2-     NO     N2O     N2 Warm, anaerobic conditions + OM promote rapid denitrification

40. GreenSeeker Technology

41. Some day soon soil testing may consist of on-the-fly “sensing” of soil hundreds to thousands of times per acre like a yield monitor

42. Justus von Liebig discovered, through the analysis of hundreds of samples of plant ash, that plants contain elements such as sodium, potassium, calcium, and phosphorus. He concluded that the minerals contained in plants must come from the soil and that without fertilization, the mineral content of soils could become exhausted, rendering the land unproductive for agricultural purposes. Law of the Minimum water Justus von Liebig (1803 -1873)

43. Slide from a recent student presentation in my upper level nutrient management class. • Soil sampling is the only manual step left in the process. With the implementation of robotic samplers, the number of samples will increase and the cost per sample will decline, thereby enhancing the economic return and the advancement of soil testing knowledge. • The are at least a dozen primary factors which impact crop yield potential. A study a number of years ago ranked soil fertility as #9! • Development of new technologies will eventually lead to new knowledge systems for managing crop production.