Applying Lime to Raise Soil Ph for Crop Production (Western Oregon)
Total Page：16
File Type：pdf, Size：1020Kb
Applying Lime to Raise Soil pH for Crop Production (Western Oregon) EM 9057 • May 2013 N.P. Anderson, J.M. Hart, D.M. Sullivan, N.W. Christensen, D.A. Horneck, and G.J. Pirelli oil acidification, or a decrease in soil pH, is Table 1.—Minimum soil pH values recommended for crops a natural process that is accelerated by crop grown in western Oregon.a Sproduction practices, primarily the use of Minimum nitrogen (N) fertilizers such as urea, ammonium sul- Crop pH fate, or other fertilizers containing ammonium-N. Alfalfa 6.5 As soil acidification occurs, soil chemical and Beans and cucurbits 5.8 Blueberries, rhododendrons, and azaleas 4.5 biological properties change. One chemical change Cereals or small grainsb 5.5–5.8 is increased solubility of aluminum (Al) and man- Christmas trees 5.0 ganese (Mn), both of which can be toxic to plants. Corn Plants vary in their tolerance of Al and Mn, creating Grain or silage 5.5 crop-specific soil pH requirements. Adding lime Sweet corn 5.8 (Figure 1) increases soil pH (reduces acidity), adds Forage and seed legumes calcium (Ca) and/or magnesium (Mg), and reduces Crimson/subterranean clovers, vetchb 5.5–6.0 the solubility of Al and Mn in the soil. Red clover for forage or seed 6.0 White clover for forage or seed 5.8 Soil pH management Garlic 6.5 Hops 5.7 The first step is to determine the soil pH required Pasture, seed, and turf grassb 5.5–5.8 for your crop. The pH at which yield is diminished Peppermint 5.6–6.0 varies among crops. Table 1 provides minimum soil Shade, ornamental, fruit, and nut treesb, c 5.5–5.8 pH recommendations for western Oregon crops. Vegetables, brassica (broccoli, etc.) 6.3 Crop-specific guidance is provided in Oregon State Vegetables, assorted for small acreage 6.5d University (OSU) and Pacific Northwest (PNW) aWhen soil pH is below the minimum value, crop yields may be reduced. Extension nutrient management guides. Other pub- bRange is given, as specific minimum pH values vary among crop species. lications in this series (Soil Acidity in Oregon and cSoil pH for red maple should not exceed 6.0. dUse this value when a small area with a variety of vegetables is produced, continues on page 3 especially when growing garlic, onions, spinach, radish, brassicas, and greens such as lettuce and arugula. Nicole P. Anderson, field crops Extension agent; John M. Hart, Extension soil scientist emeritus; Dan M. Sullivan, Extension soil scientist; Neil W. Christensen, professor of soil science emeritus; Donald A. Horneck, Extension agronomist; and Gene J. Pirelli, regional Extension livestock and forage specialist; all of Oregon State University. OSU Marion Extension County office archives Figure 1.—Lime application in Marion County, OR, about 1960. 1 Publication summary This publication describes how to estimate By-product lime products can be a cost- lime application rate and lists criteria for choos- effective substitute for traditional aglime. Their ing liming materials (source), lime application characteristics should be evaluated carefully. For method (placement), and how often to apply lime certified organic crops, use only lime approved by (frequency). your certification agency. Lime application rate is determined using the Lime application method (placement) takes lime requirement test (SMP buffer method). For two forms. Lime is either applied and left on the established perennial or no-till crops, a top-dress soil surface or incorporated. In the absence of till- lime application (1 to 2 t/a) may be benefi- age, soil pH increases only in the top inch or 2 of cial. When very different soils are present within soil since lime’s limited solubility means that the a field, variable-rate lime application is usually liming material must contact acidic soil before it advantageous. will react and change soil pH. Liming materials vary in effectiveness. The Frequency of lime application is determined carbonate in traditional aglime (calcium or mag- primarily by cation exchange capacity (CEC) and nesium carbonate) reacts with soil acidity to crop management practices, especially N fertil- neutralize it. izer rate. Soil pH declines faster in sandy (low Liming materials have very limited move- CEC) soils than in soil with moderate to high ment into the soil without incorporation. Tillage clay content. The typical rate of pH decline is increases effectiveness of all lime materials by approximately 0.1 pH unit per year when 100 lb mixing them into the rooting zone. ammonium N/a is applied. Evaluate liming materials based on effective- For annual crop rotations, apply lime about a ness (lime score) and cost. Calculate product cost year before planting the crop that is most sensitive per ton of 100-score lime. to soil acidity. For perennial crops, soil test and apply lime prior to tillage for crop establishment. Related publications This publication is the first in a three-part series. We recom- mend you use them in combination. Soil Acidity in Oregon, EM 9061 (in press) • Discusses why soil pH management is critical to long-term soil productivity. • Explains the mechanisms whereby acidity injures crops. • Gives historical perspective of what is known about soil acidity problems in Oregon soils and crops. • Explains how to use soil and plant tissue testing to diagnose soil acidity problems. Gale Gingrich Figure 2.—Lime application Eastern Oregon Liming Guide, EM 9060 in Marion County, OR, 2012. Although application equipment • Provides recommendations for lime application for dryland has changed over the decades, and irrigated cropping systems in eastern Oregon. techniques have not, and liming remains an important tool for maintaining crop yield. 2 Eastern Oregon Liming Guide) also provide target soil pH values for many Oregon crops. Terms used in this publication Next, use soil testing to monitor soil pH and determine whether lime application is needed to Ion—a molecule in which the total number of achieve your target pH. Collect soil samples at the electrons is not equal to the total number of same time each year to minimize seasonal variation. protons, giving it a net charge For annual crops established with tillage, moni- Cation—a positively charged ion tor soil pH in the 0- to 6-inch or 0- to 8-inch depth Anion—a negatively charged ion (also the recommended depth for other routine soil N—nitrogen Ammoniacal N—NH +-N analyses). 4 Al—aluminum Mn—manganese In annual crops established without tillage, and in perennial crops, soil acidity usually is greatest (pH Ca—calcium H—hydrogen is lowest) near the soil surface. Therefore, a separate Mg—magnesium K—potassium soil sample taken from the 0- to 2-inch depth can The cations, Al+3, Mn+2, Ca+2, Mg+2, H+, and K+ help in estimating lime need. See OSU Extension are used in this publication without charge desig- publication EM 9014, Evaluating Soil Nutrients and nations except when used in chemical reactions. pH by Depth in Situations of Limited or No Tillage in Western Oregon, for soil sampling recommendations CEC—cation exchange capacity, the sum for perennial or no-till cropping systems. of cations electrostatically attracted to 100 grams of soil expressed in milliequiva- Raising soil pH with lime lents (meq) Soil acidification is reversed by adding a liming Equivalent—amount of a substance that will material. Liming materials are oxides, hydroxides, react with 1 gram of hydrogen carbonates, and silicates of Ca and/or Mg. The anion Milliequivalent (meq)—1⁄ of an equivalent in liming materials (chemically speaking, a “base”) 1,000 reacts with soil acidity (H) to neutralize it (Figure 3). CCE—calcium carbonate equivalent The most common liming material, “aglime,” sup- Buffer—material that is resistant to pH change plies carbonate as the base. Slaked lime—calcium oxide that has been Calcium alone does not increase soil pH. For mixed with water, creating calcium example, gypsum (calcium sulfate) and other addi- hydroxide tives contain Ca but do not contain a basic anion Prilled or pelleted lime—finely ground agri- (carbonate, hydroxide, oxide, or silicate). Therefore, cultural lime that has been mixed into a they do not neutralize soil acidity. slurry with a water-soluble binding agent and pelletized Figure 3.—Soil acidity reacts with lime to form water and carbon dioxide. The carbon dioxide gas is lost to the atmosphere. This chemical reaction continues until all of the lime has reacted. Figure by Dan Sullivan. 3 Liming decisions Lime application rate Management decisions related to liming can be The amount of lime needed is estimated by a lime grouped into four categories: requirement test using the SMP buffer (see infor- mation below). Other lime requirement tests are • Lime application rate—how much lime is offered by soil testing laboratories, but only the SMP needed to neutralize soil acidity? test results have been validated by OSU Extension • Liming materials—what source of liming research for use with lime recommendation tables material should be used? and figures in this publication. • Application method—how should lime be As with most soil tests, the value reported using applied? the SMP buffer is only an index; it means nothing by • Frequency of application—how often should itself. To interpret the SMP test for lime requirement, lime be applied? use either Figure 5 or Table 3 (page 6). Figure 5 These decisions are discussed separately in this and Table 3 are appropriate for only a limited range publication, but keep in mind that they often are of target soil pH values. Consult crop-specific interrelated. OSU Extension guides for additional lime rate information. continues on page 6 SMP buffer test Why the name? perfect, and because soil sampling techniques add The SMP buffer test is named after Shoemaker, variability, we recommend that you use SMP as McLean, and Pratt, the soil scientists who pub- a guide for lime requirement.