Science and management of Ca and Mg


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We will discuss this presentation in my soil fertility class this coming week (October 2011).

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Science and management of Ca and Mg

  1. 1. Calcium (Ca) has an atomic number of 20 and an atomic weight of 40.08 What does Ca share in common with other elements in group IlA?
  2. 2. Calcium (Ca) has an atomic number of 20 and an atomic weight of 40.08 Ca+2
  3. 3. Radioactive fall-out from Chernobyl Sr can substitute for Ca with very unhealthy consequencesThe plume from the burning reactor initially traveled in a northwest direction toward Sweden, Finland and eastern Europe, exposing the public to levels up to 100 times the normal background radiation. Contamination of grain and dairy products was a serious concern. Both Sr-90 and I-131 migrate to vital organs in the body where they are impossible toremove, serving as a constant source of unnecessary radiation and as a cause of cancer or other diseases
  4. 4. Calcium is the 5th most abundant element in the earth’s crust element atomic number % by weight oxygen 8 46.60 silicon 14 27.72 aluminum 13 8.13 iron 26 5.00 calcium 20 3.63 sodium 11 2.83 potassium 19 2.59 magnesium 12 2.09 titanium 22 0.44 hydrogen 1 0.14 phosphorus 15 0.12 manganese 25 0.10 fluorine 9 0.08 sulfur 16 0.05 chlorine 17 0.05
  5. 5. Young Ca rich soil in IL Old Ca deficient soil in NC As a result, most young soils contain large amounts of calcium Old soils that are highly weathered and soils that formed from parent materials low in Ca tend to contain much less Ca.
  6. 6. The highly weathered soils of Brazil’sCerrado region naturally had such lowCa levels that cattle ranchers lost cattle due to brittle Ca deficient bones and large scale crop production was considered impossible.
  7. 7. > 150 million acres converted to ag since 1985, Brazil is now the #1 soybean exporter The highly weathered soils of Brazil’s Cerrado region naturally had such low Ca levels that cattle ranchers lost cattle due to brittle Ca deficient bones and large scale crop production was considered impossible. Enormous quantities of lime have been applied!! Brazilian soybean breeders have also developed welladapted soybeans varieties with high tolerance of Al toxicity
  8. 8. Forms of calcium in soil Most of the Ca in soil Plant Ca-rich minerals available Caplagioclase Exchangeable Ca+2 CaAl2Si2O8 gypsum Solution CaSO4 * 2H2O Ca+2 calcium carbonate CaCO3 All of these forms of Ca+2 Ca are linked but the Ca+2 ones on the right side of the slide are much more dynamic Calcium-organo-mineral complexes
  9. 9. For most soils, Ca+2 is the dominantexchangeable cation and cation in solution exchangeable cations in solution cations Ca+2 Ca+2 Ca+2 Ca+2 Ca+2 Ca+2 Ca+2 15 ppm Ca Ca+2 Ca+2 is adequate Ca+2 Ca+2 Ca+2 for most crops Ca+2 Ca+2 Ca+2 Ca+2 Ca+2 Ca+2 Solution concentrations of Ca in temperate region soils tend to range from ~30 to ~300 ppm. Solution concentrations are not the same as extractable (soil test) concentrations.
  10. 10. How many lbs of Ca arrive at the roots of acorn crop that transpires 20” of water during a growing season if the average soil solution concentration is 15 ppm Ca? 1 acre-inch = 27,000 gallons 1 gallon = 8.3 lbs27,000 gal/ac-in * 20 inches * 8.3 lbs/ gal = 4,482,000 lbs of H2O/ac 4,482,000 lbs * 15 / 1,000,000 = 67 lbs of CaVery few crops need more than 67 lb of Ca/ac
  11. 11. Impact of cations on flocculation of clay particles Multi-valentcations suchas Ca+2, Al+3and Fe+3 are important bindingagents at this scale.
  12. 12. Impact of cations on flocculation of clay particles In contrast, monovalentcations such as Na+ and K+ causeclay domains to disperse. What about Mg+2?
  13. 13.
  14. 14. Plant uptake of Ca commonly exceeds all other elements except for N and KMonocots generally contain less Ca (0.15-0.5% of dry plant tissue). Dicots generally contain more Ca (1-3% of dry plant tissue) Woody plants store large amounts of Ca and often have similar uptake of Ca and N. Ca movement within plants occurs mostly through the transpirational stream (water moving upward through the xylem) as opposed to in the phloem. Ca movement to growing tissues that are not transpiring (e.g.., fruits) is very restricted.
  15. 15. Calcium content of grain and stover for corn, wheat and soybeans N P205 K20 Ca Mg S Crop Yield Lbs/acre Corn (grain) 150 bu 110 53 40 2 8 10 Corn (stover) 4.5 tons 100 37 145 26 20 14 Wheat (grain) 40 bu 50 25 15 1 6 3 Wheat (straw) 1.5 tons 20 5 35 6 3 5 Soybeans 50 bu 188 41 74 19 10 23 (beans) Soybeans 6,100 lb 89 16 74 30 9 12 (stover)
  16. 16. Variation in nutrient levels in alfalfa Location N P2O5 K2O Ca Mg S lb/ton Alabama 52 12 50 19 4.5 3.3 N. Carolina 45 15 45 28 5.3 4.8 IPNI – N. Central 100 to 12 30049lbs/ac 51 > -na- 5.4 5.4 Alberta, Canada -na- 10-15 50-65 30 5-7 5-7 P. Northwest 50-70 8-16 48-72 28-35 5-8 4-6 So how much Ca is removed by a typical alfalfa crop?$department/deptdocs.nsf/all/agdex10073
  17. 17. Physiological importance of Ca Cell division and elongation Cell wall development Cell membrane function Cell protection against toxins Nitrate uptake and metabolism Activity of key enzymes Starch metabolism
  18. 18. Ca deficiency is usually associated with growing points (aka meristems) For example: buds, unfolding leaves, fruits and root tips Many fruits and vegetables have dramatic Ca deficiency symptoms such as Black Heart in celery and broccoli, Tipburn in lettuce and cabbage, White Heart or Hollow Heart in cucurbits, Blossom End Rot in tomatoes and peppers, and Pops in peanuts. Tree fruit with low calcium exhibit storage problems such asbitter-pit in apples, cork-spot in apples and pears, cracking in cherries, and other degradation of the fruit while in storage. Lack of moisture or non-uniform moisture availability is frequently associated with symptoms of calcium deficiency
  19. 19. Most commercial fruit producers inthe Pacific NW spray their apple and pear trees with CaCl2 or Ca(NO3)2. Some varieties receive 3-4 treatments, others 6-7. The application of foliar Ca is cost effective and can dramatically improve fruit quality.
  20. 20. High Response Crops The following crops have been found to be especially sensitive to Ca availability: apples, broccoli, brussel sprouts, cabbage, carrots, cauliflower, celery, cherries, citrus, conifers, cotton, curcurbits, melons, grapes, legumes, lettuce, peaches,peanuts, pears, peppers, potatoes, tobacco, and tomatoes
  21. 21. According to the U of I, Ca deficiency does not occur in Illinois when soil pH is greater than 5.5. “Calcium deficiency associated with acidic soilsshould be corrected using limestone. The laboratoryprocedure used for Ca is easy and reliable—probably more accurate than the K test— but since the deficiency does not exist, there is no reason to recommend the test”.
  22. 22. According to Tiedjens,pH measurements do not give a truepicture of the need for Ca additions
  23. 23. Low Ca and Mg levels in plant tissue were not always associated with low pH levels. High Ca and Mg levels in plant tissue were not always associated with higher pH levels. Other factors which mayhave influenced plant tissue levels of Ca and Mg include competitive cations, crop disease/injury and sub-soil pH.
  24. 24. Soil pH was clearly not the only factorimpacting plant uptake of Ca and Mg
  25. 25. Interactions with other nutrientsCompetitive cations: The relative amounts of other cations such asNa+, K+, Mg+2, NH4+, Fe+2, and Al+3 impact plant uptake of Ca+2. Additionsof large amounts of Ca+2 displace other cations from exchange siteswhich may temporarily increase their availability to crops but alsoincrease their tendency to leach. High K applications have been knownto reduce the Ca uptake in apples, which have inefficient Ca uptake andtranslocation within the tree.Phosphorus: Free or un-combined Ca is normally present in alkalinesoils. This Ca is available to interact with other nutrients. Free Ca reactswith P to form insoluble (or very slowly soluble) Ca-P compounds thatare not readily available to plants.Boron: High soil or plant tissue levels of Ca can inhibit B uptake andutilization. Calcium sprays and soil applications have been effectivelyused to help detoxify B over-applications.
  26. 26. Levels of soil test Ca and Mg (lbs/A)considered adequate for crop production Illinois Agronomy Handbook SOIL TEXTURE CALCIUM MAGNESIUM Sandy 400 60-75 Silt loam 800 150-200 A state wide (598 fields in 52 IL counties) soil fertility survey conducted in 2007/2008 reported average Ca and Mg levels of 4,452 and 732 lbs/ac, respectively. 4500 >> 800 !!
  27. 27. Why are some of these #s greater than 100%??? Portion of nutrients taken up by corn that are typically supplied by 3 main mechanisms Root Nutrient Mass flow Diffusion interception % of uptake Nitrogen <1 80 19 Phosphorous 2 5 93 Potassium 2 18 80 Calcium 150 375 0 Magnesium 33 600 0 Sulfur 5 300 0The amount of Ca and Mg brought to roots by the transpirational stream is often much greater than crop uptake
  28. 28. Why isn’t Ca uptake higher, when more is available? In contrast with most other nutrients, Ca is taken up almost exclusively by young root tips.K uptake is generally higher than Ca uptake even thoughsolution concentrations of Ca are often 10 times greater than K concentrations.
  29. 29. Impact of clay mineralogy on Ca availability Calcium availability Ca Saturation, %High CEC clays generally need > 70% Ca saturation to provide adequate Ca availability Low CEC clays generally only need 40-50% Ca saturation
  30. 30. Review of factors affecting Ca nutrition Total Ca supply Soil pH CEC % Ca saturation Relative abundance of other cations Clay mineralogyMoisture availability and uniformity of uptake New root growth
  31. 31. Many crop consultants promote Ca products! Most claims do not appear to be supported by research but Ca supplementation programs merit consideration, especially when growing “high response” crops
  32. 32. A wide range of calciumproducts areavailable onthe market.
  33. 33. Ca supplementation is likely to be of value. Tissue testing can help identify situations when
  34. 34. Calcium amendmentsLiming Material Approx. % CaCalcitic Limestone 32Dolomitic Limestone 22 When evaluating CaHydrated Limestone 46 products, carefullyPrecipitated Lime 60 consider price,Blast Furnace Slag 29 application methodCa fertilizers Approx. % Ca. and whether a liming material isGypsum 22 appropriate.CaCI2 36Ca(NO3) 2 19Ca-Chelates 3-5
  35. 35. Does gypsum improve soil structure ??
  36. 36. Ca+2 is a stronger flocculator than Mg+2 but Mg+2 is not a weak flocculator
  37. 37. Which of these soils is Ca saturated? Ca saturated Mg saturated Thin sections showing different degrees of surface crust formationAre these soils representative of real field soils?
  38. 38. Definitely not ! Ca+2 is a stronger flocculator than Mg+2 but other cations like Fe+3 and Al+3 are even stronger! Ca saturated Mg saturated Thin sections showing different degrees of surface crust formationSome crust prone soils are likely to benefit from additional Ca+2 but care should be taken to avoid creating K or Mg deficiencies through excessive Ca saturation.
  39. 39. Recent article in Journalof Soil and WaterConservation(peer reviewed scientificjournal)
  40. 40. (Norton, 2009)
  41. 41. +(Norton, 2009)
  42. 42. Large additions of Ca can cause large losses of other cations
  43. 43. Mike Starkey, Jack Maloney,Keith Schlapkohl, IN Farmer IN farmer IA Farmer Routine applications of gypsum are used by some successful farmer innovators in the Midwest region.
  44. 44. STOCKTON, IA — Keith Schlapkohlconcedes he doesnt know everythingabout farming.That hasnt stopped him from trying newthings on his Scott County farm."It seems for every one question I getanswered, 10 more are raised," he says.Schlapkohl has been trying different ideasdealing with improving nitrogen efficiencyand using gypsum on his Eastern Iowafields.During this time, his yields have averagedclose to 300 bushels per acre for corn and60 bushels for soybeans.
  45. 45. Excerpt from the Iowa Farmer Today article:“Schlapkohl believes gypsum increases production by improving water infiltration."Its chemical tillage," says Schlapkohl about gypsum.By using gypsum, he has been able to lower the magnesium levels in his soils. Highermagnesium levels tighten up the soil, he explains.Using gypsum also has increased the amount of oxygen in the soil and increased Nefficiency, Schlapkohl notes. (he has harvested >300 bu of corn/acre with less than 100lbs of fertilizer N)He uses a calcium-sulfate product from Cedar Rapids that has a higher ratio — 3:1 — ofcalcium to sulfur, compared with other sources that have a 1:1 ratio.Schlapkohl says there is more available calcium and less heavy metals in this productcompared with regular gypsum. This substance is not as powdery as typical gypsum.He has a business that spreads the gypsum product over the winter. Because he alsofarms, Schlapkohl likes to spread the product between harvest and planting and stayclose to home.”
  46. 46. Mike Starkey says his background in accounting helped him toprioritize information gathering functions at the farm, including aheavy use of on-farm trials to evaluate the impact of variousinputs.“We are not afraid to change things when we find something thatworks better,” Mike Starkey says.The Starkey family has been a no-till operation since 2000 aftertrying it briefly in the early 90s. Once he and his family learnedhow to properly set up no-till planting equipment, place nitrogenefficiently and monitor calcium and magnesium levels in soils, theoperation was successful in using no-till. Starkey echoes Maloney’s comments about water infiltrationimprovements after using Gypsoil. “It is amazing how water doesnot stand anymore. When it rains hard, water is just gone now.”
  47. 47. Figure 1. Varying degrees of clay dispersion in soils. The higher amounts of dispersal(4 and 5) indicate a soils suitability for gypsum application. No.0 displays slaking(breaking off of soil particles), compared to 1 to 5 which show clay dispersion
  48. 48. A tablespoon of any soluble salt (including table salt) will flocculate clay in a quart jar! What about the jar test?Without the addition of a flocculating agent, it is normal for fine clay to stay in suspension after soil is shaken vigorously with water.
  49. 49. Excellent review of research on the value of gypsum in humid regions
  50. 50. Green data points represent soils that responded positively to gypsumSoils which respond positively to gypsum have greater ability to adsorb both Ca+2 and SO4-2 than soils which are not responsive. This could be developed into a routine soil test.
  51. 51. Magnesium (Mg) has an atomic number of 12 and an atomic weight of 24.3 What does Mg share in common with other elements in group IlA?
  52. 52. Magnesium (Mg) has an atomic number of 12 and an atomic weight of 24.3 Mg+2
  53. 53. According to the U of I, Mg deficiency occasionally occurs in IL for both corn and soybean but is limited to sandy, low organic matter soils.Southern Illinois University research has shown no response to applied Mg even when the Mg test from the surface soil was below recommended levels. They observed that Mg levels below the surface 7-inch level were adequate and apparently met the needs for optimum crop production even when surface levels were considered deficient.
  54. 54. Magnesium deficient corn
  55. 55. Magnesium deficient tomato leaves
  56. 56. Physiological role of Mg in plants Central element of the chlorophyll moleculeEnzyme activator and a constituent of many enzymes Sugar synthesis Starch translocation Plant oil and fat formation Nutrient uptake control Increase Fe utilization Aids N fixation in legume nodules
  57. 57. The basic structure of a chlorophyll molecule is a porphyrin ring, coordinated to a central atom. This is very similar instructure to the heme group found in hemoglobin, except that in heme the central atom is iron, whereas in chlorophyll it is magnesium.
  58. 58. High Response CropsThe following crops have been found to be especially sensitive to availability of Mg: alfalfa, blueberry, beet, broccoli, cabbage, cauliflower,celery, clover, conifers, cotton, cucumber, eggplant, lettuce, onion, pepper, potatoes, pumpkin, spinach, squash, tobacco, tomato and watermelon
  59. 59. Spectrum Analytic Inc (a plant and soil testing lab in OH) analyzed thousands of plant tissue samples in 2010. The results indicate that many crops would benefit from more magnesium. In looking at the data, keep in mind that this is a biased survey. Plant samples are more often than not submitted to find out why a crop is underperforming.
  60. 60. Sources of MgDolomitic limestone is a mixture of CaCO3 and MgCO3 and is the lowest cost source of Mg but should only be applied when lime isneeded. The Mg content of dolomitic limestone varies from 8-10%. To be most effective as a source of Mg, dolimitic lime should be broadcast and incorporated. Neutral salt sources of Mg Sul-po-mag has a Mg content of 11%. The sulfur (S) and K2O concentrations are ~22%. Epsom salts = MgSO4·7H2O = 9.9% MgMgCl2, Mg(NO3)2 and Mg chelates can be used as solutions and foliar sprays
  61. 61. Cation Balancing??Proposed by Firman Bear, William Albrecht andothers prior to the advent of soil test calibration
  62. 62. Claims associated w/ “balanced” Ca:Mg ratios• Improves soil structure• Reduces weed populations• Stimulates populations of earthworms and beneficial microorganisms• Improves forage quality• Excess soil Mg “ties up” and promotes leaching of other plant nutrients• Better “balance” of soil nutrients• Improved plant and animal health• “Cows milk easier”
  63. 63. U of WI Conclusions• Alfalfa yield related to exchangeable K and soil pH, not Ca:Mg ratio• Neither Ca or Mg additions affected weeds• Earthworms related to organic matter, not Ca:Mg ratio• Alfalfa quality related to pH and stand, not Ca:Mg ratio• No justification to use calcitic over dolomitic lime or adding extra Ca
  64. 64. NCR 103 CommitteeNC Regional Publication 533Soil Cation Ratios for Crop Production – Ca and Mg levels can be balanced but too low – Field research does not support “optimal” Ca:Mg ratio conceptConcludes: “A sufficient supply of nutrient cations is the most important consideration in making economic fertilizer recommendations”
  65. 65. Many studies have evaluated the base saturation ratio concept - none have concluded that specific optimum ratios existBear, F.E., and S.J. Toth. 1948. Influence of calcium on availability of other soil cations. SoilSci. 65:67-74.Eckert, D.J., and E.O. McLean. 1981. Basic cation saturation ratios as a basis for fertilizing andliming agronomic crops: 1. Growth chamber studies. Agron. J. 73:795-799.Eckert, D.J. 1987. Soil test interpretations: Basic cation saturation ratios and sufficiency levels.In J.R. Brown (ed.) Soil Testing: Sampling, Correlation, Calibration, and Interpretation. SpecialPublication No. 21. Soil Science Society of America. Madison, WI.Graham, E.R. 1959. An explanation of theory and methods of soil testing. Missouri Agric. Ext.Stn. Bull. 734.Hunter, A.S. 1949. Yield and composition of alfalfa as affected by various calcium -magnesiumratios in the soil. Soil Sci. 67:53-62.Liebhardt, W.C. 1981. The basic cation saturation concept and lime and potassiumrecommendations on Delaware’s Coastal Plain soils. Soil Sci. Soc. Am. J. 45:544-549.McLean, E.O., R.C. Hartwig, D.J. Eckert, and G.B. Triplett. 1983. Basic cation saturation ratiosas a basis for fertilizing and liming agronomic crops. II. Field studies. Agron. J. 75:635-639.Simson, C.R., R.B. Corey, and M.E. Sumner. 1979. Effect of varying Ca:Mg ratios on yield andcomposition of corn and alfalfa. Commun. Soil Sci. and Plant Anal. 10:153-162.
  66. 66. Why no crop response to “Ca:Mg ratio” ?• Ca and Mg levels in the soil solution are normally high compared to plant uptake• Plant K uptake is 2-4 times that of Ca and Mg despite much lower levels of K in the soil solution• Roots preferentially take up K and exclude Ca and Mg.
  67. 67. K:Mg ratio may be more important than Ca:Mg ratioA number of studies (e.g., Rahmatullah and Baker (1981) and Stout and Baker (1981) have reported an inverse relationship between K:Mg ratio and Mg uptake by corn seedlingsWilkinson et al. (1987) reported that applications of high rates of K to cool season grass pastures, whether frommanure or inorganic fertilizers, increased the incidence of grass tetany. .
  68. 68. Johannsonn and Hahlin (1977) reported a stronginverse relationship between K:Mg ratio and Mg uptake by oats, and only a minor effect of Ca saturation on K and Mg uptake.
  69. 69. From the Spectrum Analytic, Inc website:1. When the soil test K to soil test Mg ratio exceeds 1.5 many crops will havetrouble taking up Mg, almost regardless of the soil Mg test level.2. When the ratio is between 1 and 1.5 some grasses will have occasional Mgproblems, and corn is the most sensitive grass species.3. When the ratio is less than 1, there are few Mg problems in any crop,assuming that the soil Mg is not initially deficient.4. When the soil pH is less than 6.0, situations described in points 1 through 3will occur at a lower soil K:Mg ratio and the Mg shortage will be more severe.5. It is rare to find an example where the soil levels of K or Mg have any effect onCa uptake.6. It is very rare to find poor Ca uptake when the soil Ca saturation is higher than50%. Some exceptions to this can be found with some crops, such as apples,that use Ca inefficiently.
  70. 70. Mg concepts Good overview of$webindex/9657B817A2FFCA5E85257723004A0967/$file/BC22010-Page-26-28.pdf