Potassium

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I shared this presentation with my Soil Fertility class in October 2011.

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Potassium

  1. 1. A group of Udon Thanis Iron Ladies shout "No Potash!", a phrase that has become their battle cry in a four year struggle against a proposed mine in their village.
  2. 2. Answer the following questions based on information in 2 readings:1) The New Thai Capitalism: Development or Disaster?http://clpmag.org/article.php?article=The-New-Thai-Capitalism-Development-or-Disaster_1622) The potash project: Thailands first underground mine – Canadian MiningJournal (abridged version should be attached)Questions:1) Who are the “Iron Ladies” and what is their mission? Do you think the age andgender of the “Iron Ladies” has affected the way Thai society, governmentofficials and industry reps have responded to their protests? What if the protestswere led by college students? or young male farmers?2) Why did the mining company lobby for changes in Thailands Mineral Act of2002? What has the mining company done to address public skepticism aboutforeign owned companies?3) Identify several potential negative environmental impacts of the proposedmining project.
  3. 3. 4) What types of technologies does the mining company plan to employ to minimizenegative environmental impacts?5) What types of public benefits does the mining company claim will come about if themine is developed? Do any of the villagers believe these claims?6) Estimate the potential economic value (in US dollars) of the Udon potash reserves.Assume 500 million tons of potash ore with an average K2O content of 20% can beeconomically extracted. Assume a world price of $500 per ton of potash fertilizercontaining 60% K2O.7) How do the 2 articles differ in their tone? (Hint: compare words used to describelocal opposition to the mine)? Do you think one article is more likely to be accurate orobjective than the other? Explain.8) How do you think members of your community would react if a mining companywanted to extract minerals from deep underneath your community and claimed thatthe mining would *not* significantly disrupt current land uses or harm theenvironment?9) As far as I can tell, mining still has not begun in Udon and the Iron Ladies haveremained unwavering in their opposition. What do you think will happen? Do you thinka compromise is possible?
  4. 4. In Latin and German, Kalium = Potassium ?Why is potassium represented by the symbol K 39K is the dominant isotope. 40K (radioactive) and 41K (stable) are used as tracers.
  5. 5. Typical quantities of nutrients in Midwest farm soils (kg/ha) Element Total Exchangeable Solution K 38,000 190 10-30 Ca 8000 2250 60-120 Mg 6000 450 10-20 N 3500 -na- 7-25 P 900 -na- 0.05-0.15 S 700 -na- 2-10 1 kg/ha = 0.89 lbs/acThe total potassium content of most Midwest soils is tens of thousands of lbs per acre-plow layer but most of the K is locked up in minerals like K feldspar that release K very slowly
  6. 6. Depth ofSo where did all loess capthis potassium come from? K-rich primary minerals A loess cap covers about 2/3rds of IL Glacial outwash
  7. 7. Cyril Hopkinswrote a ground- breaking bulletin on potassium inIL soils almost a century ago. http://www.archive.org/stream/potassiumfromsoi00hopk#page/n3/mode/2up
  8. 8. Is this possible?
  9. 9. Luxury consumption
  10. 10. Unavailable (90 to 98%) K K K+ K+ Soil Minerals Soil solution K+ (feldspar, mica) K+ K K K Readily available (0.1 to 2%) K+ K+ K+ K+ Soil Colloid Soil Colloid Trapped K K+ K+ K+ K+ Soil Colloid Slowly available (1 to 10%)
  11. 11. Important potassium concepts No significant gaseous forms3rd most likely (after N and P) to be plant limiting Non-toxic at high concentrations Does not promote eutrophication (unlike N and P)
  12. 12. Role of potassium in plant nutritionRemains in ionic form inside plants (rather than being incorporated into organic molecules) Very important osmotic regulator (lowers water potential inside of plant cells) Activator of over 80 enzymes 1-4% of plant dry matter (similar to N) Important for tolerance of environmental and biotic stresses (drought tolerance, winter hardiness,resistance to fungal pathogens, resistance to insects)Important for crop quality (flavor, color, stem strength)
  13. 13. Necrotic leaf margins are associated with potassium deficiency
  14. 14. K deficiency symptoms can occur even when soil test K levels are high Corn in ridge-till and no-till systems are often first to show K deficiency symptoms, but they can occur in other tillage systems as well. Uptake of K by plants requires an active root system, especially in the soil zone where plant-available K is located !!When this soil zone is dry, uptake is limited. Anything that exerts additional stress or limits root growth--compacted soil layers, root pruning, side-wall smearing--further reduces K uptake, especially when root growth is restricted in the zones of highest available K.
  15. 15. Crop removal of K by grain crops is small compared to forages
  16. 16. Vegetable crops use a lot of potassium !Crop Yield N P2O5 K2OBell Peppers 180 cwt 137 52 217Cabbage 20 tons 130 35 130Peas 25 cwt 164 35 105Potatoes (white) 30,000 lb 90 48 158Snap Beans 4 tons 138 33 163Sweet Corn 90 cwt 140 47 136Tomatoes 20 tons 120 40 160 Many veggies use more K2O than N!
  17. 17. Average K2O application rates for fruit and vegetable crops in the US
  18. 18. Fertilizers do not actually contain K2O1 lb of elemental K = 1.2047 lbs of K2O Crops do not actually take up K2O
  19. 19. The more highly weatheredsoils in southern IL tend to have low CECs. Pockets of sandy soils (grey shaded areas) in northern and central IL also have low CECs Most soils in the “high” region shown on this slide have CECs 12 centimols / kg. 1 centimol/kg = 1 meq / 100 g Most soils in the “low” region shown on this slide have CECs < 12 centimols / kg. The U of Ilinois recommendshigher soil test K for soils with higher CEC!
  20. 20. Crop response to extractable K in low CEC soils No maintenance Sufficiency
  21. 21. Crop response to extractable K in highCEC soilsCrop response to extractable K in low CEC soils No maintenance Sufficiency
  22. 22. Iowa State has updated their K recommendations for corn and soybeans How do you convert between ppm and lbs/acre?
  23. 23. Variation in soil test K critical levels across the US and Canada http://www.ipni.net/ipniweb/portal.nsf/0/c13f0cf310f1903e062577c7005a4bd7/$FILE/2010%20Critical%20P%20and%20K%20Maps.pdf
  24. 24. Why do different states have different soil test critical levels? Part of the reason is differences in soils but climate, cropping systems and data interpretation philosophy also matter.
  25. 25. Some labs recommend much higher K levels for soils with high CECs http://www.spectrumanalytic.com/support/library/ff/Soil_test_P_and_K_buildup_and_drawdown.htm
  26. 26. Soil testing methods for potassium used by US labs in 2005Traditional method Universal extractant adopted by moreNH4+ exchanges with labs every year K+ on soil colloids
  27. 27. Soil Test K survey results (> 4 million samples from ~ 60 labs)Change between 2005 and 2010 % of samples below critical level Declines in many states but not IL
  28. 28. Soil test values for K fluctuate during the year K is more available in wet soils
  29. 29. Drying of moist samples increases soil test K
  30. 30. General rule of thumb:4 lbs of K2O are required to raise soil test K by 1 lb
  31. 31. Annual application vs. build up and maintenance
  32. 32. Some soils have high K fixation capacity
  33. 33. Economic response to K fertilization is most likely when soil test K is low and K fertilizer is cheap relative to the price of corn. K fertilizer is cheap relative to grain prices high medium K fertilizer is expensive low relative to grain prices low high
  34. 34. What really happens to fertilizer K? Only 20 to 60% of applied K is taken up by crops in year 1 Highest recovery on low K soils Why?? Slowly Available K Unavailable K Available K The K in KCl (muriate of potash) is near 100% plant available but is not the only source of K (and other cations) in the soil. Also, crop roots normally explore a much larger volume than the zone of amendment
  35. 35. Relationship Between Soil Test K Level and Yield Response to Starter Fertilizer in WI - 1995 100 QRP 80 y=343-6.82x+0.034x2 if x<100 Yield response, bu/acre 60 y=0 if x>100 R2=0.52 n=54 40 20 0 -20 VL L O H EH -40 (47) (19) (-2) (8) (1) 50 100 150 200 250 Soil test K, ppm www.soils.wisc.edu/extension/teachingmaterials/Wolkowski/RowPlacedFertilizer2004.ppt
  36. 36. Relationship between temperature and maximum soil test K level where yield response occurred to starter fertilizer 2500 Air temperature departure ,oF 1995 y = 1119 - 0.84x + 0.00017x2 1 2400 R2 = 0.97 Cumulative GDD 2300 0 2200 1994 -1 2100 1993 1996 2000 -2 100 110 120 130 Critical soil test K level, ppm www.soils.wisc.edu/extension/teachingmaterials/Wolkowski/RowPlacedFertilizer2004.ppt
  37. 37. Compaction affects nutrient uptake !Potassium Affected Most• Compaction reduces porosity and limits root growth• Lowers soil O2 and slower replenishment from the atmosphere• O2 needed for root respiration and active uptake of K• Compacted soils are often responsive to K fertilization www.soils.wisc.edu/extension/teachingmaterials/Wolkowski/RowPlacedFertilizer2004.ppt
  38. 38. Row K Effects on Corn Yield with Increasing Soil Compaction Initial K Soil test = 102 ppmwww.soils.wisc.edu/extension/teachingmaterials/Wolkowski/RowPlacedFertilizer2004.ppt
  39. 39. Plant analysis for K in soybean leaves at R1 can be a useful tool foridentifying K deficiencies. Critical levels ranging from 1.2 to 1.7% K have historically been recommended in many Corn Belt states. It now appears that higher K levels are needed in conservation tillage systems. (Yin and Vyn, 2005) Leaf samples consisted of the most recently fully developed trifoliate leaves, including the petiole, collected from 20 plants at R1 in mid- to late-July from each plot
  40. 40. It’s well documented that alfalfa will take-up K beyond its needs if high levels of soil or applied K areavailable. This is referred to as “luxury consumption”.
  41. 41. Soils containing highlevels of magnesium and calcium generally needhigher levels of potassium to maintain high crop yields due to competitive ion effects.
  42. 42. High soil test K:Mg ratios Over many years of looking at plant analysis samples, we have seen that where the soil test ratio (lb:lb) of K:Mg is greater than 1.5:1; many crops are likely to suffer Mg shortages. This is often in spite of the soil having "adequate" amounts of Mg in the soil. Where the soil test ratio of K:Mg is between 1:1 and 1.5:1, grass crops, including corn may be at risk of an Mg shortage. While such an induced Mg deficiency can reduce yields, it is possibly a bigger problem for livestock that consume the green chop or silage. When these high soil K:Mg ratios are combined with low to marginally sufficient Mg and/or acid soils, the probability of Mg deficiency increases.http://www.spectrumanalytic.com/support/library/ff/Potassium_basics.htm
  43. 43. Does Cation Balance Matter? http://www.pda.org.uk/leaflets/6/no6-print.htm The relative concentration of potassium, calcium, magnesium,ammonium, and other positively charged ions in the soil solution influences their relative uptake. Excessively high concentrations of one cation often results in inadequate uptake of other cations.For example, very high concentrations of calcium reduce uptake Grass tetanyof potassium and very high concentrations of potassium reduce magnesium uptake. Cation balance affects animal health
  44. 44. Potassium Fertilizers K 2O ChemicalMaterial Content Formula % “Potash” = muriate of potash = MOP guaranteedpotassium chloride KCl 60 analysissul-po-mag K 2 SO 4 2MgSO 4 20potassium nitrate KNO 3 44potassium sulfate K 2 SO 4 50Used in organic agriculture
  45. 45. Potassium fertilizer sales in IL Material fall06 spring07 0-0-60 207,410 143,041MOP 0-0-62 92,880 86,821 99.1 % of material grade 569,491 tons 94% of total
  46. 46. The chloride in MOP hasnegative effects on some crops Tobacco fertilized with MOP produces cured leaves with muddy and uneven color with excessive hygroscopicity and poor burn.
  47. 47. MOP is salty stuff !
  48. 48. White potash is produced of KCl, NaCl and other salts. and Potash ore is a mix by a process of dissolution The KCl is concentrated using a flotation process whichrecrystallization. Potash ore is dissolved under pressure in skims off the surface of a fluid suspension of finely hot brine, and MOP is precipitated further processed and crushed ore. This concentrate is as the brine cools andpressure reduces. resulting fertilizer materialthis process, and screened. The The iron is removed in is ~ 95 percentthe resulting MOP fertilizer isbecauseWhite MOP is generally MOP. It is reddish in color white. iron impurities in the at least are not removed in this process. ore 98 percent potassium chloride.
  49. 49. Global K fertilizer production and consumption Total world production = 33 million metric tons of K2O in 2007
  50. 50. http://minerals.usgs.gov/minerals/pubs/commodity/potash/mcs-2008-potas.pdf
  51. 51. Canada has the largest potash reserves and also exports the most potashTotal global economic reserves ~ 8 billion metric tons
  52. 52. PotashCorp produces 23% of the worlds supply of potash.PC also controls most of the worlds unused supply, and hashistorically held back production to keep potash prices high.
  53. 53. PC is the worlds largest fertilizer company#1 in potash, #3 in phosphate and #4 in nitrogen fertilizers
  54. 54. How much does potash cost in IL this fall?
  55. 55. Potash prices were up about $5.50 a ton last week in Illinois, with the average price at $639, ranging from $600 to $710. Illinois prices remain about $25 a toncheaper than Iowa, which is more in line with our forecast models, which puts spring prices at $690 a ton.
  56. 56. Why does Potash track differently than Ammonia and DAP?

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