Anhydrous ammonia, ammonium nitrate, ammonium sulfate, cyanamide, nitrate of soda, urea, and nitrolime are all used as sources of nitrogen in this region. Anhydrous ammonia supplied about 50 percent of the total in 1956. Ammonium nitrate furnished slightly more than 25 percent.

Anhydrous ammonia can be applied successfully on any soil that is in good tilth. It is difficult to apply ammonia on soils in poor tilth, particularly heavy clay soils, because ammonia must be sealed in the soil simultaneously with its injection. Other forms of nitrogen will usually prove more efficient on those soils and also, in most instances, when close-growing crops are to be top-dressed. Again, sealing the ammonia in the soil is the limiting factor. If sealing can be done, ammonia will prove equal to other sources.

Most of the nitrogen is supplied by acid-forming sources. Because the pH ranged from 5.3 to 6.8 on most of the alluvial soils in 1956 and the loessial terraces were somewhat more acid, it seems certain that lime eventually will be required to neutralize the acidity. Few alluvial soils showed a response, however, except when some legumes are grown, and tests have not indicated that the acidity is increasing so fast as theoretical calculations imply.

A much higher percentage of the loessial soils need lime.

In this area, where several of the nutrients exist in abundant amounts, the "balanced nutrient" idea has little or no practical application. It is important that each nutrient be supplied in adequate amounts, but no evidence exists to indicate that any given ratio must obtain between them under field conditions. Nitrogen is the only major nutrient that will be particularly harmful if it is used to excess.

Even with nitrogen, the balancing must be with the plant and not with other plant nutrients.

CROP PRODUCTION is the ultimate objective of a soil-management program. For maximum yields and maximum efficiency in production, crops must be grown on soils to which they are adapted, or sufficient treatment must be applied to an unadapted soil to overcome the natural limitations.

The latter approach assumes that information is available to prescribe the necessary treatment. This was not the case in 1957 in the Delta region. It is desirable that the knowledge of soil management be increased sufficiently to make economics the factor that determines whether a crop should be be grown on a given soil. In view of the present level of knowledge, however, practical considerations dictate that crops be grown on the soils where they are best adapted. The selection of the soil type must be followed up with other soil-management practices.

Cotton, soybeans, corn, oats, wheat, barley, alfalfa, sugarcane, rice, and pastures occupy more than 96 percent of the open land in the region.

Cotton is the leader. It is best adapted to the fine sandy loam, loam, and silt loam soils that have good internal drainage, but it can be grown profitably on most of the soils where surface drainage can be provided. Land preparation should be limited to the necessary tillage to provide a good seedbed tillage should be deep when hardpans exist. Cultivation should be limited to the amount necessary to eliminate any crusting and to control weeds. Nitrogen must be supplied by legumes or by commercial fertilizers on all soils. The optimum rate ranges from 60 to 120 pounds of nitrogen an acre. Most soils may need the higher rate. Some soils need phosphorus and potash. The need to rotate cotton and high-residue crops or sod crops increases as the soil becomes finer.

On some of the better sandy loam soils, cotton can be grown continuously for an indefinite period if erosion is controlled, fertility is maintained at a high level, minimum tillage is practiced, and all tillage is done when soil moisture is favorable.

Soybeans rank second to cotton here. They grow equally well on fine sandy loam to clay soils. If satisfactory stands are obtained, the yields on clay soils are less variable and less affected by drought. Generally no fertilizer is needed except on loessial terrace soils, where potash is frequently deficient. We have no evidence that rotations are beneficial. In fact, some observations indicate that yields of soybeans tend to increase by successive cropping. Soybeans are especially susceptible to hardpan conditions.

Small grains are particularly well adapted to this region. Oats are better adapted to the lighter soils, although satisfactory yields can be produced on the clay soils. Wheat is adapted to most of the soils but is better suited to the clay soils than oats. Barley is adapted to the lighter soils but is limited by diseases in most of the southern part of the region. All three, especially barley, require good surface drainage. Nitrogen is the only plant nutrient generally required; 45 to 60 pounds of nitrogen an acre usually are best. The inability of the plants to resist lodging limits the rate of application. Nitrogen should be applied as a topdressing in late February or early March. Rotation with other crops may be necessary, particularly in the case of barley and wheat, to control disease.

The soil-management requirements for corn are essentially the same as those I listed for cotton, except that slightly higher rates of nitrogen (120 pounds an acre) are required. Lack of attention to production practices is the primary reason for low average corn yields in this region. Corn is well adapted, and average yields of more than 50 bushels an acre are attainable.

Alfalfa is planted on a larger acreage in the Delta region than any other hay crop. It is well adapted to silty clay and clay soils. Lack of surface drainage has been one of the chief causes of failure. In order to insure drainage where fields do not have uniform slopes, the soil should be formed into lands 50 to 130 feet wide and 8 to 14 inches high. A well-prepared, firm seedbed is necessary. Many of the soils require lime. Some need phosphorus and potassium. Most of the soils near the Mississippi River, however, are adequately supplied with all plant nutrients.

More sugarcane is grown in this region than in any other part of the United States. The acreage is concentrated largely in the lower part of Louisiana. Drainage is a major problem. Nitrogen is the one nutrient that must be generally applied.

Rice is adapted to clay and silty clay soils and to silt loams that have a compacted layer. The soil characteristics must be such that water movement through the profile is restricted. A rotation system is more necessary for rice than for any other crop grown in the Delta. Weed control is the primary purpose for the rotation, although improved structure and increased nitrogen are important secondary effects. The cropping sequence should provide for 1 to 2 years in rice and 1 to 3 years in lespedeza, soybeans, or pasture. One new and apparently promising rotation in some parts of Arkansas consists of 2 years in rice and 1 to 2 years of water fallow. A water level of 2 to 4 feet is maintained during the fallow period, and a crop of fish is produced. Nitrogen is the major nutrient that must be applied. Phosphorus may be needed on some soils. Lodging limits the rate of nitrogen application. The natural soil conditions and the present knowledge of management practices suggest a great potential rice production here if the market should demand it.

Pastures occupy 10 to 15 percent of the open land. The acreage has expanded rapidly since 1948. Most of the expansion has been on the silty clay and clay soils, except in places where a 3- to 5-year rotation with other crops is practiced. Establishment is a major problem, largely because of crusting and cracking of the soils. Land preparation in the fall and early spring seeding tend to minimize stand failures. Mixtures of grasses and legumes afford the most economical pastures, and ones which generally require little or no fertilization. Red clover and Johnson-grass for the lighter soils and tall fescue and Ladino clover for clay soils are two examples of adapted mixtures. Under intensive management systems where high forage production in late spring and summer is required, Coastal Bermuda-grass and Johnsongrass offer the best possibility. Each grass will require irrigation and the application of the equivalent of 1 pound of nitrogen a day during the growth period.

Soil management is seldom the limiting factor in pasture production. Rather, lack of knowledge of pasture crops and livestock management have usually limited the development of the pasture-livestock program.