Liming Materials --- Conversion to Metric Units --- Useful Links Comments and recommendations presented in this section are based on growing conditions in Oregon's varied producing regions (see Oregon Production). Oregon potatoes are 100% irrigated. All production sites east of the Cascades are semi-arid with annual precipitation levels of around 10 inches or less. By contrast, Willamette Valley fields may receive from 40 to 60 inches between October and May in any given year; it seldom rains appreciably in the Valley between early June and the end of September.. Those of you in other production regions, particularly rain-fed areas, should keep these generalities in mind as you evaluate recommended fertilizer practices relative to your local situation:Western Oregon--primarily the Willamette Valley--is characterized by extremely wet winters, springs, and sometimes early falls. Summers are usually clear and dry with cool nights. The growing season is relatively short and yields are only average. Consequently, recommended rates for the western part of the state are relatively low compared to the Columbia Basin and Malheur County.
- Central Oregon and the Klamath Basin are high and dry with relatively short growing seasons. Planting usually begins in early May and harvest is concentrated in September and early October. Yields are slightly above average for the U.S. but below average for Oregon. Fertilizer recommendations tend to resemble those of the Willamette Valley.
Western Oregon - West of Cascades
- The Columbia Basin and Malheur County are characterized by extremely long growing seasons and very high yields. Fertilizer recommendations tend to be higher in the Columbia Basin than in Malheur County because much of the Basin is covered by extremely sandy soils with low fertility but extremely high yield potential when properly managed. Planting sometimes begins as early as late February in the Hermiston-Boardman area.
Potatoes respond well to optimum fertilizer levels in terms of both yield and quality. However, too much fertilizer, especially nitrogen, can over stimulate vine growth and delay tuber set and maturity. Delayed maturity, in turn, can lead to reduced starch and elevated sugar levels at harvest causing crops to be poorly suited for processing. Immature plants are also difficult to vine kill and tubers from such plants are typically thin-skinned and extremely susceptible to mechanical injury during harvest. Excessive mechanical injury can seriously complicate storage to the point that uncontrollable decay can occur. Experienced potato people understand that it is vitally important that fertilizer rates and timing be well suited to the production area, the intended length of season, and the intended market.Crops grown for processing into either chips or french fries must have high starch (high solids, high specific gravity) for acceptable product texture and freedom from oiliness. At the same time, reducing sugars (glucose and fructose) must be relatively low to prevent brown discoloration of fried products. Because of these strict requirements, fertilizer (especially nitrogen) rates for processing crops are frequently 10 to 20% lower than for similar crops intended for table use. It is important that very little of the nitrogen complement be applied to processing crops late in the season to avoid delayed maturity and adverse effects on starch and sugar levels.
Because of the extreme leachability of nitrates and public concerns about groundwater quality, irrigation programs must be precisely tailored to crop needs. The potato is shallow-rooted with 90% or more of the root mass typically in the top foot of soil. Nitrogen leached below the top foot is therefore largely unavailable to the crop and subject to leaching. Some sandy Oregon potato soils hold less than an inch of available water per foot. Extreme precision is required to maintain adequate soil moisture without leaching on such soils. Obviously, heavy rains or over irrigation can leach much of the available nitrogen below the rooting zone in any potato field in Oregon.
Fertilizer rates depend on a number of factors including time of harvest, variety, plant population, previous crop, and intended use. A soil test is the most accurate guide for planning fertilizer programs. Petiole analysis is also extremely valuable for monitoring crop nutrient status during the season, especially for leachable elements in long-season production areas such as the Columbia Basin. Petiole analysis is a useful tool for monitoring fertility declines following unusually heavy rainfall or other wet situations.
Crop nutrient usage is closely allied to yield. The following table shows approximate lbs of elements removed in potato tissues at several yield levels. Actual crop usage depends on a number of factors in addition to tissue removal. Irrigation/precipitation regimes can dramatically impact some elements such as nitrogen.
Approximate Lbs. of Nutrient Elements Removed per Acre
1Nutrient removal in vines also varies somewhat in relation to yield because larger yields typically require proportionally large vine biomass.
Cwt of Tubers/Acre Nutrient Vines1 300 400 500 600 Nitrogen 139 128 171 214 257 Phosphorus 11 17 23 29 35 Potassium 275 144 192 240 288 Calcium 43 4.4 5.9 7.4 8.9 Magnesium 25 8.9 11.8 14.7 17.6 Sodium 2.70 1.74 2.32 2.90 3.48 Zinc 0.11 0.11 0.14 0.18 0.22 Manganese 0.17 0.04 0.06 0.07 0.08 Iron 2.21 0.79 1.06 1.32 1.58 Copper 0.03 0.06 0.08 0.10 0.12 Boron 0.14 0.04 0.05 0.06 0.07 Accurate records of past fertility trends for fields in question can also be useful for planning fertilizer programs. Bear in mind that full-season crops require more fertilizer than early-harvested plantings and that crop yield and fertilizer needs are roughly proportional.
Every effort should be made to thoroughly sample each field and plan fertility programs accordingly. Your local County Extension Agent can provide soil sampling instructions, bags, and information sheets.
Growing season applications of nitrogen either through the irrigation system or soil-applied are less effective in short-season areas than in long-season regions such as the Columbia Basin or Treasure Valley. Considerable research at the Klamath Experiment Station, for example, has shown little value in post-emergence N applications whereas nitrogation and other seasonal application methods have been shown to be highly effective in the Columbia Basin. Seasonal N applications, or so-called "spoonfeeding", based on systematic petiole sampling combined with occasional soil samples, is highly recommended for maximum N use efficiency and groundwater protection in the Columbia Basin and Treasure Valley.
Before proceeding further, you may want to investigate general information on fertilization, nutrient management, groundwater quality and so forth provided by other web sites (see Useful Links below). The Cornell Nutrient Analysis Laboratories provide an excellent discussion of various non-crop-specific aspects of nutrient management including the nitrogen cycle and sources and roles of nutrients. Information on liming and production of forages is also presented.
Except for editorial changes, the following is based on OSU Extension FG (Fertilizer Guide) 19. P, K, Mg, B, and lime guides are based on soil test values. Because of unpredictable and usually heavy spring rains, soil tests are not extremely reliable predictors of early season nitrogen needs in Western Oregon. However, summer soil and petiole analyses are highly desirable for monitoring crop health and establishing standards for future reference.This guide is derived from experiments and field trials conducted by T.L. Jackson, J.T. McDermid, and Arden Sheets, Agricultural Experiment Station, and Willard Lighty, Robert Smith, Harold Werth and Hugh Gardner, Extension Service, OSU.
Original text was prepared by E. Hugh Gardner and T.L. Jackson, Soil Science and A.R. Mosley, Crop Science, Oregon State University Extension Service and Agricultural Experiment Station. Preliminary drafts were reviewed by a committee of Western Oregon county extension agents.
Potato yield and quality depend on good management of. fertilization; irrigation; insect, weed and disease control; and other cultural inputs. Fertilizer application affects specific gravity (starch content), size and smoothness of tubers as well as yield.
This fertilizer guide assumes good management. See Conversion to Metric Units.
NITROGEN (N)
Potatoes respond markedly to N in western Oregon; however, excess N can delay maturity, resulting in poor storage and reduced tuber starch (lower solids, specific gravity).
N fertilizer rates depend on: time of harvest, variety, plant population, previous crop, possible leaching losses due to over-irrigation, and whether the crop is intended for processing or fresh market.
The following fertilizer suggestions apply to mineral soils; potatoes require less N on peats or mucks.
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Lbs/a |
Kg/Ha |
Lbs/A |
Kg/ha |
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60-120 |
65-135 |
120-200 |
135-225 |
Row Crops or Legumes |
50-100 |
55-110 |
80-120 |
90-135 |
PHOSPHORUS
(P)
Potatoes usually respond to band applications of P. P should be banded
3 inches (7.5 cm) to one or both sides and slightly below seedpieces at
planting. P rates are typically based on soil analysis of the plow layer.
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POTASSIUM
(K)
Potatoes require high levels of available K. K is most effective if
banded at planting as described for N and P. K2O in excess of
100 lb/A (110 kg/ha) should be plowed down.
If Soil Test for K Reads (ppm): |
Apply this Amout of K2O |
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SULFUR
(S)
Potatoes have a relatively high requirement for S. S deficiency is common in soils in Western Oregon. Include 40 lbs/A (45 kg/ha) of S in the annual fertilizer program. S is sometimes contained in fertilizers used to supply other nutrients such as N, P, and K, but possibly not in sufficient quantity.
Plants absorb S in the form of sulfate. Fertilizer materials supply S in the form of both sulfate and elemental S. Elemental S must convert to sulfate in the soil before it becomes available to plants. The conversion of elemental S to sulfate is usually rapid for finely ground (less than 40 mesh) material in warm, moist soil.
Elemental S should be applied the year before potatoes using finely ground (less than 40 mesh) material. S in the sulfate form can be applied at planting.
Some S fertilizer materials such as elemental S and ammonium sulfate have an acidifying effect on soil.
MAGNESIUM
(Mg)
Some western Oregon soils contain relatively low levels of available Mg. High calcium and/or K levels can reduce Mg uptake by potatoes. Where calcium levels equal 10 to 15 meq/100 g soil or higher and/or K levels are 600 ppm or higher, the probability of a response to Mg is increased.
If the soil test value for Mg is less than 1.5 meq/100 g soil, band 10 to 20 lbs/A (10 to 20 kg/ha) of Mg at planting. More than 20 lbs Mg/a in the band may reduce yield.
Mg can be applied in the form of dolomite lime which is equal to ground limestone in reducing soil acidity.
BORON
(B)
Potatoes have not responded to applications of B in experimental plots in western Oregon. Some growers, however, have reported favorable responses.
A trial application of 1 lb/A (1 kg/ha) of B may be useful when the soil test value for B is below 0.5 ppm.
Do not include B with banded fertilizer. Apply B as a broadcast application ahead of planting or as a foliar spray early in the season. Potatoes are very susceptible to injury from over-fertilization with B.
OTHER
MICRONUTRIENTS
With the possible exception of B, responses of potatoes to applications of micronutrients have not been observed in western Oregon.
LIME
Potatoes have responded to experimental applications of lime on very acid soils in the north Willamette Valley.
Liming is suggested when the OSU soil test for calcium is less than 4 meq/100g soil and the pH is below 5.5.
If the lime application raises the pH of the soil above 6.0, there is a possibility of encouraging potato scab. When possible, lime should be added immediately after potatoes in the rotation, or at least 6 months prior to planting and should be worked into the soil.
If Buffer Test for Lime Reads |
Apply this Amount of Lime |
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A lime application is effective over several years.
Dolomite lime, which can be used as a source of Mg, is equal to ground limestone in reducing soil acidity.
In OSU Fertilizer Guides, English and metric units are used. The abbreviations
and Conversion Factors (C.F.) are:
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Columbia Basin and Malheur County
The Original paper version of FG 57 was prepared by E. Hugh Gardner, James Burr, and Darrell Maxwell, Extension Service; and T.L. Jackson and E.N. Hoffman, Agricultural Experiment Station, Oregon State University, Corvallis.
Specific recommendations are based in large part on experiments conducted by T.L. Jackson, Tom Davidson, E.N. Hoffman, and Luther Fitch, Oregon Agricultural Experiment Station, and on experience in growers fields.
Good management practices are essential if optimum fertilizer responses are to be realized. These practices include use of recommended varieties and good seed, selection of adapted soils, weed control, disease and insect control, timely harvest, and most importantly, optimum irrigation.
In potato production, both quality and yield are important. Potato quality is primarily a function of management inputs. Fertilizer applications and timely irrigation affect the yield, specific gravity (starch content), size, and smoothness of tubers. This fertilizer guide assumes good management.
It is important that the soil be sampled and tested as a guide to fertilization.Follow recommended soil sampling procedures to insure satisfactory fertilizer recommendations. Your County Agent can provide instructions and forms.
See also Conversions
NITROGEN
(N)
Potatoes require a good supply of available N, however, excessive rates of N can reduce potato quality and delay maturity.Nitrogen requirements depend on: length of the growing season; the preceding crop; N carry-over from the previous crop; the plant population; the amount and type of residue plowed under; and possible leaching losses due to over-irrigation or heavy rain.
Of the suggested N application, 40 to 100 lbs N/A should be banded at planting (the urea and diammonium phosphate forms of N may cause seedpiece and sprout injury if banded close to the seed). The remainder of the N should be plowed down, injected, applied through the sprinkler system, or side-dressed.
The following fertilizer guides are for mineral soils.
N
Fertilizer Guide Based on Soil Test
The amount of residual N in the soil varies considerably. A soil test for nitrate-N (NO3-N) helps in evaluating N carryover from previous crops on mineral soils with low organic matter. However, nitrogen soil tests are of limited value following alfalfa.
Soil samples should be taken from the 0-24 in. soil depth.
Soil samples for soil test N should be taken following a growing season
and prior to the application of n fertilizer.
NO3-NTest to 24", ppm |
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Mal. Co. |
Co. Basin |
Mal. Co. |
Co. Basin |
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N
Fertilizer Guide Based on Previous Crop
Where a soil test is not used (not a recommended practice), N fertilization should be based on the preceding crop.
Previous Crop |
Nitrogen Application, lbs/acre |
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Mal. Co. |
Co. Basin |
Mal. Co. |
Co. Basin |
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PHOSPHORUS
Potatoes usually respond to the application of P, particularly when the soil is cold as with early planted potatoes. P applications are based on a soil test of the plow layer.
P should be banded about 2 to 3 inches to one or both sides of the seed
at planting.
If Soil Test for P Reads (ppm): |
Apply P2O5, Lbs/A |
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Plow down applications of P are not as effective as band applications. For plow down applications, P rates should be should be increased by 50 percent.
POTASSIUM
(K)
Potatoes require high levels of available K. K is most effective if banded at planting time. K20 applications in excess of 100 lbs/A should be plowed down or side-dressed 6 to 10 in. from the row after planting. On some coarse sandy soils, K is broadcast.
K soil tests are usually taken from the plow layer.
If Soil Test for K Reads (ppm): |
Apply K2O, Lbs/A |
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SULFUR
(S)Plants absorb S in the form of sulfate. Fertilizer materials supply S in both sulfate and elemental forms. Elemental S must convert to sulfate in the soil before it is available to plants. Conversion is usually rapid for fine ground (less than 40 mesh) material in warm, moist soil. Elemental S should be used only on soils with pH of 7.0 or higher and applied the year preceding the potato crop using fine ground (less than 40 mesh) material.
S in the sulfate form can be applied at planting.
Apply 25-40 lbs S/A annually to potato fields which do not receive adequate S from the irrigation water.
ZINC
(Zn)
Response to Zn has been reported on cut areas of leveled fields where calcareous subsoils have been exposed.
If the soil test value for Zn is less than 0.8 ppm, broadcast and plow down or disc in 10 lbs Zn/A or 3 to 4 lb Zn/A can be included with the N banded at planting. Banding N with Zn increases Zn uptake.
OTHER
NUTRIENTS
Potato response to manganese has been reported for some crops on sandy soil in the Columbia Basin. Mn should be banded with N at planting or sprayed on the foliage.
Boron has been applied to some potato fields. Boron should not be applied at a rate in excess of 2 lbs/A and should be evenly applied to the field. Boron should never be banded.
Potato response to lime has not been observed in Malheur County or the Columbia Basin.
OSU N, P, K, and lime fertilizer guides are based on soil test values.
Good management practices are essential for optimum fertilizer response. These practices include use of recommended varieties and good seed; selection of adapted soils; suitable weed, disease and insect control; timely harvest; and, perhaps most importantly, optimum irrigation. .
In potato production, both quality and yield are important. Quality is primarily a function of management factors. Fertilizer application and irrigation affect the specific gravity, size, and smoothness of tubers. This fertilizer guide assumes good management.
It is important that the soil be sampled and tested as a guide to fertilization. Follow recommended sampling procedures to insure accurate fertilizer recommendations. Your County Agent can provide instructions and information forms.
See also Conversion to Metric Units.
NITROGEN
(N)
Potatoes require a good supply of available N, but excessive rates can reduce potato quality and delay maturity.
Of the suggested N application, 60 to 100 lbs/A (65-110 kg/ha) should be banded about 3 inches to the side(s) and slightly below seedpieces. Urea should not be banded because of possible seedpiece and plant injury. The remainder of the N should be plowed down, injected, applied through the sprinkler system, or side-dressed.
N requirements depend on: the preceding crop; N carry-over from the previous season; plant population; the amount and type of residue plowed under; and possible leaching losses due to heavy rains or over-irrigation.
The following recommendations are intended for mineral soils.
N Fertilizer
Recommendations Based on Soil Tests
Residual soil N varies considerably. A soil test for nitrate-N (NO3-N) helps in evaluating carry-over on mineral soils with low organic matter.
N soil tests are of limited value following alfalfa.
Soil samples for N should be taken from the 0-24 in. (0-60 cm) profile, or the entire depth of soil, whichever is less. Sampling depth should be reported on the information sheet.
Soil samples for soil test N should be taken after the growing season
and before the application of N fertilizer.
NO3-N to 24", ppm |
Soil N Application1/ |
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N Fertilizer
Guide Based on Previous Crop
Soil tests should always be used in planning fertilizer programs. When
a soil test absolutely can not be used, N fertilization should be based
in large part on the preceding crop.
Previous Crop |
Nitrogen Application |
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PHOSPHORUS
(P)
If Soil Test for P is (ppm): |
Apply this Amount of P as P2O5 |
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P should be banded at planting time as described for N. Plow down applications of P are less effective than banding. For plow down, P rates should be increased by 50 percent.
POTASSIUM
(K)
Potatoes require high levels of available K. K is most effective if banded at planting. K2O applications in excess of 100 lb/A (110 kg/ha) should be plowed down or side-dressed 6" to 10" (15 to 25 cm) from the row after planting. K is broadcast on some coarse sandy soils.
The K soil test is based on a sample of the plow layer.
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SULFUR
(S)
S requirements l vary with soil texture, leaching losses, the soil parent material, and soil organic matter. Pumice soils in Central Oregon have a particularly high S requirement.
In Central Oregon, 80 to 100 lbs/A (90-110 kg/ha) of S should be applied annually to coarse sandy loams and loamy sands; 40 to 60 lbs A (45-65 kg/ha) of S should be applied annually to silt loams and finer-textured soils.
In Klamath County, 25-40 lbs/A (30-45 kg/ha) of S should be applied annually.
S is frequently contained in fertilizers used to supply other nutrients and may be present in irrigation water, which can be tested for S content.
Plants absorb S in the form of sulfate. Fertilizer materials supply S in the form of sulfate and elemental S. Elemental S must convert to sulfate in the soil before it is available to plants. The conversion of elemental S to sulfate is usually rapid for finely ground (less than 40 mesh) material in warm moist soil.
Elemental S should be applied the year before potatoes using finely ground (less than 40 mesh) material.
S in the sulfate form can be applied at planting. Some S fertilizer materials, such as elemental S and ammonium sulfate have an acidifying effect on soil.
MAGNESIUM,
LIME, AND MICRONUTRIENTS
In Klamath County potatoes have responded to applications of copper and manganese on muck soils. These nutrients can be banded at rates of 1 lb/A (1 kg/ha) for copper and 5-10 lbs/A (5-10 kg/ha) for manganese.
Increased soil acidity, particularly in sandy soils, has been observed in central Oregon and Klamath County. This acidity has largely resulted from the use of acidifying N and S fertilizers.
Where the soil pH is 5.5 or less, a trial application of 1 T/A (2.25
Tm/ha) lime is suggested. The lime should be applied and thoroughly mixed
with the surface 6" (15 cm) of soil several months before planting potatoes (see also Conversion
to Metric Units).Top
of
Page
Home PIE
The following document was recreated from Oregon State University Fertilizer Guide FG 3, Liming Materials for Oregon,originally prepared by E. Hugh Gardner, Soils Specialist, Extension Service, Oregon State University, Corvallis, Oregon and reviewed by a committee of Oregon County Extension Agents and representatives of the OSU Agricultural Experiment Station and the lime industry. See also Conversion to Metric Units.
The quality of liming material is related to its degree of fineness or particle size, the chemical composition or calcium carbonate equivalent, and the moisture content.
Fineness Factor
The Fineness Factor is related to the particle size of a liming material. The particle size affects the rate at which a liming material goes into solution in the soil. Lime does not neutralize acidity or release its nutrients until it has dissolved. Lime particles which are less than 7/100 (7 hundredths) of an inch in diameter (particles of this size will pass through a 10 mesh screen) are considered to be soluble enough to be effective. Liming material particles which do not pass a 10 mesh screen are considered to be relatively non-effective. The degree of solubility increases as the particle size decreases from 10 to 40 mesh with lime particles which pass a 40 mesh screen being given the maximum solubility rating. Solubility ratings for different particle sizes are given in the table below. Liming materials are given a Fineness Factor value based on particle size. Fineness Factor values are calculated as indicated below.
Calcium Carbonate Equivalent
The Calcium Carbonate Equivalent is an expression of the acid neutralizing value of a liming material compared to pure calcium carbonate. Pure calcium carbonate is given a rating of 100.
Calcium Carbonate Equivalent of Some Liming Compounds
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The lime score of a dry liming material is a numerical expression of the quality of the dry lime and takes Fineness Factor and Calcium Carbonate Equivalent into account.
Calcium Carbonate
Fineness
Lime Score =
Equivalent
x Factor
100
A sample calculation of a Lime Score value is given below.Top of Page
Lime Score Sample Calculation
Analysis of Liming Material Sieve Analysis
Passing 10 mesh 98% Passing 20 mesh 92% Passing 40 mesh 78% Passing 60 mesh 67%Calcium carbonate equivalent (neutralizing power) = 92%
Calculation of Lime Score
Particle Size Group |
Percent in Particle |
Solubility |
Fineness |
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Lime Score = Calcium Carbonate Equivalent x Fineness Factor = 92 x 88.2 = 81.1
Moisture Factor
As water does not reduce acidity, the acid neutralizing value of a liming material decreases on a weight basis as the moisture content increases.
The Moisture Factor
= 100 - % water in lime
100
A liming material containing 15% water would have a moisture factor
= 100 - 15 = 0.85
100
Amount
of Liming Material to Apply
Liming recommendations are based on 100-score,
dry liming material. The amount of liming material to apply should be calculated
as follows:
100
x
1
x Recommended Tons/A of Lime = Tons/Acre of Material
Lime Score
Moisture Factor
As an example, if a liming material had a lime score of 81.1 and a moisture content of 15% (moisture factor = 0.85)and the recommended liming rate was 3 T/A, then:
The rate of application of liming material = 100
x 1 x 3
= 4.3 T/A
81.1 0.85
Liming recommendations are based on soil test results and vary with the soil and crop. A one ton/acre application of 100-score dry ground limestone supplies about 2 milliequivalents of calcium/100 grams of soil to the surface six inches of a mineral soil.
Chemical Composition of Liming Materials
Liming materials vary in chemical composition. The chemical makeup of lime has an effect on its neutralizing value and nutrient content. Ground limestone, for instance, consists of calcium carbonate and is a source of calcium. Dolomitic limestone consists of calcium carbonate and magnesium carbonate and is a source of both calcium and magnesium. Some liming materials may contain other plant nutrients.
Kinds of Liming Materials
Several different kinds of liming materials are available in Oregon. These include:
--Ground Limestone
Consists of calcium carbonate and varying amounts of impurities. This material sometimes contains small amounts of magnesium carbonate. Pure calcium carbonate (calcite) contains 40% Ca.
--Dolomitic Lime
Consists of varying proportions of calcium carbonate and magnesium carbonate and varying amounts of impurities. The calcium carbonate content can vary from 5% to 55% the magnesium carbonate content from 33% to 52%, and the magnesium content from 9% to 15%.
Dolomitic lime is commonly recommended as a liming material for acid soils which are deficient in magnesium.
--Hydrated Lime
Sometimes referred to as slaked lime or builder lime. Consists of calcium hydroxide with varying amounts of impurities. It is a white powder which reacts quickly when mixed with moist soil.
--Burned Lime
Sometimes referred to as quick lime or unslaked lime. It consists of calcium oxide and often impurities. It is a white, caustic powder which reacts quickly when mixed with moist soil. Thorough mixing with the soil is important in order to prevent the formation of granules which may harden and be unavailable.
--By-Product Liming Materials
Effective liming materials are produced as by-products of industrial processes such as the manufacture of cement, pulp, sugar, calcium carbide, etc. These by-products contain varying amounts of calcium and magnesium compounds and other materials. Some of the names used for these by-product materials are--sugar lime, Cotrell lime or dust, lime sludge, carbide lime and pulp mill lime.
“Best Management Practices for Profitable Fertilization of Potatoes” This publication represents the collective wisdom of a number of scientists working on potatoes in PNW over the past 30 years.