CIRCULAR ANR-503 (08/88)

A L A B A M A    A & M    A N D    A U B U R N    U N I V E R S I T I E S ALABAMA PRODUCTION GUIDE FOR NON-IRRIGATED CORN

     Soil testing to determine lime and fertilizer requirements is basic for good corn yields. Fall sampling is best since it allows plenty of time to do any needed liming and fertilizing. Take samples from the full depth of the plow layer.
      In areas that are routinely tested, one soil test can represent 20 acres or more as long as the entire area is similar with regard to soil type, drainage, and past treatment. In areas which have not been tested recently, take one soil sample from about every 10 acres.

Lime. Low pH is one of the most frequent causes of poor corn yields in Alabama. Acid soils can result in reduced root growth, reduced nutrient availability, toxicities of some elements, and poor activity of some herbicides. For good corn growth, maintain the soil at a pH of 5.8 to 6.5. Base your lime applications entirely on soil test recommendations. Any needed lime will be most efficient if applied and incorporated 2 to 4 months before planting, but application and incorporation just before planting is helpful if earlier application was not made.
Phosphorus and potassium. Most Alabama soils require an application of phosphorus and/or potassium for good corn production. The amount needed will depend on the fertility status of the soil as indicated by soil testing. A shortage of either potassium or phosphorus can limit yields. Current Auburn University recommendations call for 40 pounds per acre of both phosphate and potash on soils testing medium for both nutrients and 60 pounds per acre on soils testing low for both nutrients.
Nitrogen. Fertilization with adequate levels of nitrogen is required for good corn grain production on all Alabama soils. The cost of nitrogen is the largest single variable cost in corn production. Carefully consider the rates used and the method of application for each management system. No other element produces such large and consistent increases in corn yields. For economical returns, larger quantities of nitrogen are normally required than are needed of any other element.
     Grain yields respond to high levels of nitrogen application in years when rainfall is abundant and distributed throughout the growing season. There is also a strong interaction between nitrogen fertilization and plant population with regard to grain yield. Low plant populations frequently limit grain yield in situations where soil moisture and levels of nitrogen fertilization are high enough to produce good yields.
     The optimum economic rates of nitrogen fertilization are usually near, but may not be identical to, the rates that result in the maximum-yield response. At high application rates, additional nitrogen may produce a slight yield response, but this may not be enough to pay for the additional expense. A worksheet for determining optimum rates of nitrogen is shown below.

Standard rate	120 pounds per acre
For productive sandy soils, add 30 pounds.
If crop follows good soybeans (greater than 40 bushels per acre), subtract 30 pounds.
If crop follows a good winter legume, which is turned under, subtract 30 pounds.
If dryland yield potential is greater than 150 bushels per acres, add 60 pounds.
If crop is irrigated, add 60 pounds.
If starter fertilizer is used, add 20 to 30 pounds.
Total nitrogen recommended for season (final rate should not exceed 200 pounds per acre).

Timing and sources of nitrogen. The corn plant takes up nitrogen throughout the growing season, but the period of most rapid uptake is just before and during the silking and tasseling period. If all of the nitrogen is applied at planting time, much of it may be lost to leaching or denitrification, especially on deep sandy soils with poor drainage. These losses can be reduced by applying about one-third of the total nitrogen at planting and sidedressing and broadcasting the remainder in one or more applications when the plants are about knee-high. Different sources of nitrogen should be equally effective if application requirements are met and equal units of nitrogen are applied (See Table 1).

Table 1. Common Nitrogen Fertilizers For Corn.

Secondary micronutrients. Apply at least 10 pounds of sulfur per acre at planting. This is particularly important on sandy soils of the sandstone plateau of northern Alabama. Because sulfur deficiencies are most likely to occur early in the season, a starter fertilizer containing sulfur is the most effective way of applying sulfur. Blended or granular fertilizers containing sulfur may also be broadcast before planting.

     Zinc deficiencies occur primarily in early spring on sandy soils where the pH is above 6.0 or when lime has recently been applied. To avoid this problem, apply 3 pounds per acre of zinc at planting. A starter fertilizer would be the most effective way of applying zinc, but it can be broadcast with other complete fertilizers.
Starter fertilizers. Starter fertilizers provide readily available nitrogen and phosphorus to young corn plants in early spring when growing conditions may not be ideal. Use starters when planting very early in cold soils or when planting in minimum till or no-till systems. Starter fertilizers promote earlier maturity, aid in weed control by promoting early vigorous growth, and sometimes result in a yield increase.
     Apply 20 to 30 pounds per acre of nitrogen (N) and 20 pounds of phosphorus (P₂O₅) in a band 2 to 3 inches below and 2 to 3 inches to the side of the seed. Fertilizer may be dribbled to the side of the row at planting or applied in a subsoil slit just below the seed, but these methods are not as effective as banding. Sulfur and zinc may be effectively applied in the starter fertilizer. A complete granular fertilizer such as 13-13-13, a liquid such as 10-34-0, or nitrogen solutions may be used as starters. Research in Alabama has shown that most of the crop response is to the nitrogen and only occasionally to the phosphorus.

     Conventional methods of seedbed preparation may involve either plowing, chiseling, disking, harrowing, or combinations of these tillage operations. The purpose of tillage is to control weeds. Any unnecessary tillage is an expense that cannot be recovered.
     Deep tillage, deep chiseling, and in-row subsoiling have become popular with some growers in recent years. These techniques are likely to be beneficial when they break through a zone of soil compaction or hardpan that would otherwise restrict root growth.
     Deep tillage operations are likely to have little or no beneficial effect in fields that don't have compaction problems or where the compacted zone is too deep to be broken through. Crops grown on sandy soils of the coastal plains are most likely to respond to deep tillage. Crops grown on the fine textures soils of the Black Belt and the Tennessee Valley are not likely to respond to subsoiling.
     No-tillage planting is being successfully used by some Alabama producers, and the acreage of no-till corn appears to be increasing in the state. Reductions in erosion losses and in the number of trips over a field, as well as saving time during planting, make no-till planting attractive to many growers. No-till systems require timely management and should not be undertaken without first investigating the management requirements. For additional information on tillage practices, see Extension Circulars ANR-811, "Conservation Tillage For Corn In Alabama" and ANR-41, "Tillage To Correct Soil Compaction".

     Do not select your hybrids based on yielding ability alone. Hybrids which have good yielding ability can vary considerably in other important traits such as lodging resistance, maturity, and resistance to disease.
     Yielding ability is a complex trait and is influenced by many environmental factors. It is not unusual for the performance of a particular hybrid to vary considerably from year to year depending on weather conditions and disease and insect incidence. For this reason, the use of data from a single year may be misleading.
     Detailed information on yields and other variety performance traits is available in the annual Corn Hybrid Performance Report published by the Department of Agronomy and Soils, Alabama Agricultural Experiment Station, Auburn University. Copies of the current report are available at your county Extension office.

     Do not plant corn until the soil temperature at a depth of 2 inches is 55° F or above and there is little danger of a freeze or heavy frost. With these points in mind, the following dates are suggested for planting corn in Alabama:

     Planting in late February may be desirable along the Gulf Coast.
     Place corn seed deep enough to obtain favorable moisture conditions for germination but shallow enough to allow for quick emergence. At early planting dates when soils are moist and cold, plant corn at a depth of 1 to 1½ inches. Check the planting depth and seed spacing periodically during the planting operation.

     Corn grain yields can be markedly reduced by very low plant populations. Yield reductions due to an extremely high population can occur but are much less frequent in Alabama than reductions due to low populations. Optimum plant populations for corn are influenced by a number of factors including:
Hybrids. The optimum population differs from hybrid to hybrid. Recently released hybrids tend to do best at populations somewhat higher than older hybrids.
Fertility levels. Increased populations are often needed to obtain the maximum benefit from high fertility levels (especially high N levels).
Planting dates. Corn planted very early tends to be shorter at maturity than later-planted corn. Such corn tends to lodge less and generally benefits from slightly higher populations.
     Before making a decision regarding the plant population for a particular field, consider the many factors that influence optimum population. Non-uniform stands and low plant populations frequently limit corn yields in Alabama. Most non-irrigated hybrids will produce highest yields at populations of 16,000 to 24,000 mature plants per acre.
     The two ways to alter plant populations are: 1) to vary spacing within the rows; or 2) to vary row widths. Various combinations of seed spacing and row widths to obtain different plant populations are indicated in Table 2.

	Table 2. Seed Spacing To Obtain Various Plant Populations.
	Population Seeds Planted Per Acre* Inches Apart In The Row Row Width (Inches) 30 36 38 40 42 16,000 18,000 20,000 22,000 24,000 26,000 28,000 18,000 21,200 23,500 25,900 28,200 30,600 32,900 11.00 9.75 9.00 8.00 7.50 6.75 6.25 9.25 8.25 7.50 6.75 6.25 5.75 5.25 8.75 7.75 7.00 6.25 5.75 5.50 5.00 8.25 7.50 6.75 6.00 5.50 5.00 4.75 8.00 7.00 6.25 5.75 5.25 5.00 4.50 * Assuming that 85 percent of the seeds produce plants.

     Table 2 indicates the needed seed spacing based on the assumption that about 5 percent of the planted seed will not produce mature plants due to germination failure and stand loss to insects, diseases, and other causes. Under poor seedbed conditions and under no-tillage planting conditions, the percentage of seed failure may be even higher. Under such conditions, increase seeding rates to allow 20 to 25 percent seed failure.
     In past years, most corn was produced in rows spaced 38 to 42 inches apart, and most of the production and harvesting equipment available was designed for these widths. Research and farm experience in recent years, however, has indicated that yields may be increased when row widths are reduced below 40 inches.
     The higher the level of management, the more likely it becomes that narrowing rows will have a positive impact on yields. If equipment is available which will harvest narrow rows (30 to 40 inches), it is usually an advantage to use narrower row widths.

     The use of soil insecticides-nematicides is not recommended as a routine precautionary measure for all corn in Alabama. There are several situations, however, where their use may be beneficial. If soil insects or nematodes are known to be a problem in a field at planting time, treatment is suggested. Treatment may also be justified in high-risk situations such as irrigated corn grown at high fertility levels, very early planted corn, or no-till corn. Always follow label directions in applying such materials.

     Good weed and insect control is essential for producing high yields of corn. Weeds compete not only for water but also for nutrients and sunlight. Insects can also cause serious yield reductions in corn in Alabama. For more information on weed and insect management, see Extension Circular ANR-500A, 2002 Alabama Pest Management Handbook, chapter "Corn Insect, Disease, Nematode, And Weed Control Recommendations".