The establishment of favorable soil moisture conditions through drainage or irrigation is an important consideration, especially in the production of crops of high value.

Natural drainage of the soils varies from excessive to very poor. Removal of excess water from the poorly drained soils is necessary. The somewhat poorly drained soils are easily drained with shallow ditches at frequent intervals.

More elaborate systems, including dikes, main canals, and numerous lateral ditches, are required in areas of poorly drained soils.

Winter vegetables, the principal crops grown under irrigation, are irrigated even on soils that must be drained.

The well to moderately well-drained soils of central Florida are droughty, especially during dry periods in spring. Runoff and erosion are of minor importance in the region. Some erosion may occur on the sloping areas that have shallow, sandy clay loam and sandy clay subsoils. Contour cultivation is recommended on steeper slopes.

Severe wind erosion in some areas of the well-drained sands occurs during the winter and spring, when the soils are bare. Moving sand does considerable damage to young crops, but one can reduce its force by leaving strips of winter cover crops, such as lupine and small grains, across the field at frequent intervals at right angles to the direction of the prevailing wind.

Leaching losses may be serious on the well-drained and moderately well-drained soils, which are used for citrus, watermelons, and such general field crops as corn, peanuts, flue-cured tobacco, and pasture grasses. Liming to pH 5.5 or above and growing winter cover crops are recommended to reduce such losses.

Most of the mineral soils respond to additions of nitrogen, phosphorus, and potash. The organic soils require little or no nitrogen fertilization but need relatively large amounts of phosphorus and potassium. Mineral and organic soils, particularly those that are strongly acid or are poorly supplied with calcium or magnesium, respond to additions of lime.

Because of the low buffer capacity of most of the mineral soils, lime is applied with caution so as to avoid injury, which has been associated with heavy applications of lime on some well-drained sands. Consequently the tendency has been to avoid using lime, and some soils have become strongly acid. The liming of acid soils nevertheless has increased markedly.

Certain long-continued practices to control insects and diseases may produce unfavorable conditions. For example, the use of sulfur sprays and dusts on citrus trees permits accumulations of sulfur in the soil; it is readily oxidized and leached to produce subsoil acidity, which is not easily controlled by surface applications of lime. The treatment of the soil with sulfur to control scab of potatoes and the use of acid-forming fertilizers often bring about conditions unfavorable to the growth of the nitrifying organisms. Maintaining the soil reaction at pH 5.4 gives good control of scab and permits fairly rapid nitrification. Extremely acid to strongly acid sands have low phosphorus-fixing power; applied phosphate is lost readily by leaching until they are limed.

Deficiencies of the secondary elements appear to be less general than those of the elements required in larger amounts, but they demand equally as much attention in some circumstances.

Magnesium deficiency is most pronounced in the sands, especially those in well-drained areas, where it is responsible for bronzing of citrus.

Copper deficiencies have been noted on raw organic soils in the Everglades and elsewhere and in many areas of mineral soils. Applications of copper in those places help control dieback and ammoniation of citrus and promote normal growth of pangolagrass, oats, peanuts, and other field crops.

Marl frenching of citrus trees and the occurrence of similar leaf patterns in the foliage of various other plants growing on marl or other high-lime soils and on some of the well-drained sands indicate a deficiency of manganese.

Zinc deficiencies, which show up as frenching of citrus, bronzing of tung, rosette of pecans, and white bud of corn, are rather general. The addition of small amounts of boron is an aid in the production of celery and clovers on Leon and similar soils in the Flat-woods of central and southern Florida.

Response to applications of the trace elements has not been determined for all the various soils and crop combinations in the region. It is possible that deficiencies of them are more widespread than we have realized. Until more specific information is obtained, the use of trace elements for all crops on all soils is not recommended because of the additional expense and the possibility of building up toxic concentrations. Preliminary results of research indicate that large amounts of copper have accumulated in citrus groves as a result of applying too much copper in fertilizers and sprays.

More than a million tons and 851 grades of mixed fertilizer were used in Florida in 1955. Of the total tonnage, 199 grades accounted for 96 percent, 34 accounted for 73 percent, and 11 accounted for 51 percent.

The tendency to operate fertilizer mixing plants on a prescription basis has grown, but certain ratios and grades are used generally for fertilization of the various classes of crops on mineral and organic soils.

Grades with ratios of 0-1-3, 0-1-2, 0-1-1, or 0-2-1 are used for almost all crops on organic soils. The amount of potash is less as the length of period in cultivation increases. Sugarcane on organic soils gets potash only.

Ratios of grades used for production of various crops on mineral soils are approximately as follows: Corn, cotton, small grains, pearlmillet-1-2-2 or 1-3-3, with nitrogen sidedressing; leguminous field crops 0 1 1, 0-1-2, 0-1-3, or 1-4-4; flue-cured tobacco--1-3-3 or 1-3-4; grass pastures 1-2-1 for establishment and 1-1-1 alternated with nitrogen only for maintenance; vegetables 1 1 1 or 1-2-2, with nitrogen or 1 0 1 sidedressing; citrus-1-1-1, 2-1-2, or 1-0-1, with magnesium.

The ratio of the grades of mixed fertilizers used on most bearing citrus groves has changed gradually since the early 1930's from 1-2-1, to 1-1-1, to 2-1-2, and finally to 1 0-1. This change followed the discovery that phosphorus accumulates in sandy soils that are maintained at the proper pH level. It seems desirable to make this type of change in the fertilization of other crops on soils on which large amounts of phosphorus have been used.