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 Corn Production and Management of Saline and High pH Soils
Key Points
• Nutrient availability to sustain
corn plant growth can be affected
by inadequate pH levels.
• An optimum pH for corn growth is
between the range of 6.0 to 6.5.
• Seed germination and/or plant
growth can be reduced by high
salt concentrations.
Soil pH and Impact on Corn Production
Soil pH is a logarithmic scale used to measure the acidity (lower pH) or alkalinity (higher pH) of soil. Because of
the logarithmic scale, an increase or decrease in the pH value of 1 unit results in a 10-factor change in acidity or
alkalinity. Nutrient availability to sustain corn plant growth can be affected by inadequate pH levels (Figure 1). The
generally accepted optimal pH value for corn production is between the range of 6.0 to 6.5. In addition, the
performance of certain herbicides and other chemicals can be influenced by soil pH. 1 The Eastern Corn-Growing Area is generally typified by low pH soils; however, the Western Corn-Growing Area is
prone to high pH situations. High pH problems for corn production generally start at a pH > 7.8 and are typically
saline (salty), sodic, or a combination of saline and sodic (Table 1). Saline soils can develop when: 1) rising water
tables bring salt to/or near the soil surface, 2) irrigation water contains high levels of salts, 3) intensity of row crop
production increases, 4) an abundance of rainfall occurs, and no-till is adopted.2 Sodic soils generally have a pH >
8.5 and saline/sodic soils range between 7.8 and 8.5.
Table 1. Classification of salt-affected soils.3
Saline Soils
Field 1. Nutrient availability based on pH.
Saline or salty soils result when there is a high concentration of soluble cations Ca+2, Mg+2, K+1, Na+1 (lesser
extent) and the anions SO4-2, NO3-1, and Cl-1 in the soil.5 The most common salts are sodium sulfate (Na2S04),
magnesium sulfate (gypsum, MgSO4), sodium chloride (NaCl), calcium (Ca), and magnesium chloride (MgCl2).4
Saline soils usually appear the same as neutral soils; however, the soil surface may appear powdery at times.
Source: Illinois Agronomy Handbook. Permission granted for
use by Dr. Emerson Nafziger, University of Illinois.
Seed germination and/or plant growth can be reduced by high salt concentrations. Seedling injury symptoms
resemble those that can occur when seeds are placed too close to row-applied fertilizers or are burned from
anhydrous ammonia. Since high pH can reduce the availability of zinc (Zn), iron (Fe), and phosphorus (P) (Figure 1), plants may show foliar deficiencies for these nutrients.
Zinc and Fe deficiencies appear as yellow stripes on middle to upper leaves (Figure 2). Purplish or dark green lower leaves and stem are typical signs of P deficiency (Figure
3). Plants growing under high pH conditions can appear droughty because water moves from areas of low salt content to high salt content. High pH irrigation water can burn
leaves, particularly the youngest leaves.
Management for saline soils begins with a soil test to determine the electrical conductivity (EC). An EC reading of 4 deciSiemens per meter (dS/m) or 4 millimhos/cm
(mmhos/cm) or more defines a saline soil. The two measurement terms are used interchangeably and are equal. After identification, management centers around controlling
the movement of water towards the soil surface. The installation of drainage tile helps reduce the movement of water to the soil surface. However, approval to drain salty
water into a stream or other source may be required and may not be granted. Soil EC can decrease 0.5 dS/m for every 6 inches of water that percolates through the soil.5
One inch of rainfall can help reduce salt concentrations by 50 percent in the top 1-to 2-inches.4 If tillage is practiced, it should be done shallowly and fallowing should not be
practiced if available water in the top 4 feet of soil is sufficient to grow a minimal crop, or if soil texture is sandy loam or coarser in nature.4
Corn Production and Management of Saline and High pH Soils
Corn products differ in their tolerance to saline soils; therefore, conversations with your Channel Seedsmen can be beneficial to help identify the most saline tolerant
Channel® brand products for planting. Fields, unproductive for corn growth, may benefit from the planting of crops such as alfalfa or native grasses such as switchgrass that
have deep penetrating root systems that can help cycle salts back into the subsoil and lower the water table.4,5 Crops ranked by their ability to limit the discharge of
saltwater through seepage to lower areas are alfalfa > sweet clover > sunflower, safflower, sugarbeet > barley, wheat, soybean, durum wheat and canola.4 Planting when
the salt levels are the lowest from snowmelt or spring rains can be beneficial.4,6 Sodic Soils
Sodic soils contain high concentrations of exchangeable Na and low concentrations of total salts. Symptoms
associated with sodic soils include:
•
•
•
•
Specific toxicity to Na sensitive plants.
Nutrient deficiencies or imbalances associated with high pH, often above 9.0 (Figure 1).
Dispersion of soil particles causing the soil to become poor in physical structure.
Water intake is poor, especially with soils high in silt and clay.7 Sodic soils are measured by the sodium adsorption ratio (SAR), which is the ratio of the amount of cationic
(positive) charge contributed to a soil by Na, Ca, and Mg. If the SAR is above 13, the soil is classified as sodic.
High Na levels may also be reported as a percentage of exchangeable Na (ESP). A value >15% is typical for
sodic soils, which means that Na occupies >15% of the soil’s cation exchange capacity (CEC).7 Sodic soils
tend to be hard and cloddy when dry and crust easily. Black alkali is dark dusty material on the soil surface
and is caused when organic matter, dispersed and dissolved in the soil solution of highly sodic soils, is
deposited on the soil surface by evaporation.7
Figure 2. Typical striping associated with zinc
deficiency.
Managing sodic soils consists of changing the growing crop to a more tolerant species or crop or changing the soil chemistry. Changing the soil chemistry involves replacing
exchangeable Na with Ca. The two main types of amendments for Na replacement include products that dissolve soil available limestone or gypsum and through the direct
application of Ca (gypsum or CaCl) to the soil.7 Soil lime or gypsum can be dissolved by applying sulfur (S) or sulfuric acid. Elemental S and sulfuric acid lower pH and
dissolves lime and gypsum, which increases Ca concentrations. Theoretically, 1 ton of gypsum is replaced by 380 lbs of elemental S (0.19 X 2000 lb/ton = 380 lb S).5 Calcium added to the soil should be mixed into the soil and followed by the addition of water to leach the Na beyond the root zone. The recovery of an acre of sodic soil at a
depth of 1 foot requires about 1.7 tons of pure gypsum for each milliquivalent of exchangeable Na present in 100 grams of soil.7 The incorporation of crop residues, manure, compost, cover crops, and green manure can help improve soil tilth and water infiltration. Deep plowing to move Ca upward,
tiling, and the use of tolerant crops rather than fallowing have also been utilized to help reclaim sodic soils.
Sources
1
Fernández, F. G. and Hoeft, R.G. Managing soil pH and crop nutrients. Chapter 8. Illinois Agronomy Handbook. University of
Illinois.
2 Malo, D.D., Clay, D.E., Reese, C.L., Clay, S.A., Owen, R., Kharel, T., Birru, G., Green, J., and Desutter, T.M.* 2015. Saline
and sodic soils: Characteristics and properties. Saline/Sodic Soil Management Workshop. Redfield, SD. South Dakota State
University. *North Dakota State University.
3 Waskom, R.M., Bauder, J.G., and Andales, A.S. 2012 (Revised). Diagnosing saline and sodic soil problems. 0.521. Colorado
State University Extension.
4 Franzen, Managing saline soils in North Dakota. SF1087. North Dakota State University.
5 Carlson, G., Clay, D., Malo, D., Clay, S., and Reese, C. Saline (salts) and sodium problems and their management in dryland
corn production. South Dakota State University.
6 Gullickson, G. 2014. Saline and sodic soils can be fixed. Successful Farming at Agriculture.com.
7 Davis, J.G., Waskom, R.M., and Bauder, T.A. 2012 (Revised). Managing sodic soils. Fact Sheet No. 0.504 Colorado State
University Extension.
Other sources: Soil pH. Soil quality kit - guide for educators. USDA. NRCS. United States Department of Agriculture.
Mengel, D.B. 1993. Fundamentals of soil cation exchange capacity (CEC). Agronomy Guide. AY-238. Purdue University
Websites verified 3/31/17 170324144433 Figure 3. Purpling associated with unavailable
phosphorus.
For additional agronomic information, please contact your local seed representative. Developed in partnership with Technology Development & Agronomy by
Monsanto.
Individual results may vary, and performance may vary from location to location and from year to year. This result may not be an indicator of results you may obtain as local growing, soil and weather
conditions may vary. Growers should evaluate data from multiple locations and years whenever possible. Always read and follow grain marketing and all other stewardship practices and pesticide label
directions. All other trademarks are the property of their respective owners. ©2017 Monsanto Company. 170324144433 04262017LGM