Of Kentucky's 25 million acres of land, about 15 million acres are potentially suitable for agricultural cropland use, either for row crops, hay and meadow crops, or permanent pasture crops. Of this 15 million acres, about 1 million acres has no limitation as to crop suitability or cropping patterns. The remaining 14 million acres have variable degrees of limitation for crop use; this land is either steep enough that soil erosion is a hazard or relatively flat where soil wetness is a problem.
On a statewide basis, erosion hazard is by far the greatest limitation for use of cropland with about 11.4 million acres (about 75% of the total cropland acreage) being subject to such risks. For this reason, cropping systems, patterns and management have to be devised to decrease soil erosion to levels which will not reduce the crop production potential on this 11.4 million acres of potential cropland. Tables 1 and 2 summarize Kentucky's land base in this respect.

Table 1. Characterization of Kentucky's Land Base According to Cropland Use Limitations¹

Land Class	Cropland Use Hazard	Acres (millions)
I	none	0.998
II	erosion	3.366
II	wetness	0.932
II	droughty	0.140
III	erosion	2.970
III	wetness	0.885
III	droughty	0.065
IV	erosion	2.160
IV	wetness	0.202
IV	droughty	0.040
VI	erosion	2.876
VI	droughty	0.305
TOTAL ACRES CROPLAND		14.939

¹ Agricultural Production Potential for Kentucky, U.K. College of Agriculture

Table 2. Characterization of Kentucky's Agricultural Cropland According to Land Use Suitability¹

Potential Land Use	Acres (millions)
Cultivated Row Crops	5.9
Hay and Meadow	5.5
Permanent Pasture	3.5
TOTAL CROPLAND POTENTIAL	14.9

¹ Agricultural Production Potential for Kentucky, U.K. College of Agriculture

Developing Agricultural Land Use Patterns
Although soil erosion potential is the greatest land use hazard statewide, in developing agricultural cropping programs, each individual farm tract must be specifically evaluated for its cropping suitability. Some tracts may have little erosion potential, while others may have severe erosion potential. Soils maps prepared by the U.S. Department of Agriculture Soil Conservation Service are the best source of information on the characteristics of soils which occur on any particular land tract. There are published modern soil survey reports for about three-fourths of Kentucky counties. Any tract of land within those counties can be located and an appraisal of the soils made. For tracts of land which occur in counties without published modern soil surveys, soils maps of individual land tracts are often available, particularly if the landowners have been Soil Conservation Service cooperators. Advice on evaluating the soils base for crop production is available both from local county extension offices as well as from local USDA-SCS offices. Although soil erosion may not be a land use problem on some farm tracts, most tracts in Kentucky do have an erosion risk, varying from slight to severe.
For this reason, most farm producers should consider agricultural land use practices which provide some means of soil erosion control. Many such practices are in widespread use, particularly the agronomic practices which cost less to install than engineering practices. Those of particular use to Kentucky farmers include no-till planting, winter cover crops, sod waterways, crop residue management (including chisel-plowing), contour planting and cropland rotations. Proper use of these practices makes it possible to utilize the land to its full potential for row-crop production. And since annual row crops are potentially more valuable than most perennial agronomic crops, it is row crop production which largely determines maximum potential returns per acre.
Therefore, the basic economic principle underlying development of a cropland use system should be to use land to its potential. This principle implies that, for economic purposes, an opportunity for additional income is lost if land suitable for row-crop production is not used for that purpose. It also implies that land not suitable for row crop production be used for the best suited perennial crop for a particular field-either for hay, meadow or permanent pasture. Use of rotations together with modern production practices makes it possible to more fully utilize land with an erosion hazard for maximum row-crop production.

Cropland Rotations
Cropland rotations are not new to Kentucky farmers. But with recent advances in row crop production technology and with the ever-shrinking profit margin on farm production of agricultural commodities, many Kentucky farmers have increased their row crop production acreage. Sometimes, this has been done without considering soil erosion effects either on land iii-suited for row crop production or on land requiring special conservation practices for producing row crops.
While sod waterways, winter cover crops, contour planting and strip cropping are not new practices, their proper use with no-till, planting or residue management makes possible the development of more intensive row crop production systems on land with an erosion hazard. By using these practices together with cropland rotations, much potential Kentucky cropland susceptible to erosion can be used more profitably without damage to the soils base.

Benefits From Cropland Rotations
Soil Erosion Control - if used in proper rotation, sloping land with a moderate to severe hazard for erosion (fields generally with an average slope of 6-20 percent) can be used for higher value row crop production more often without undue soil erosion losses.
Soil-Borne Pest Control - Many economically destructive soil-borne insects and disease organisms can be more effectively controlled by periodic crop rotation together with any justifiable chemical pest control rather than chemical pest control alone.
Better Weed Control - Periodic rotation, particularly for row crops in fields where chemical weed control is always used, will provide a better long-term, broad-spectrum weed control.

Units of Cropland Rotation
The field is the basic management unit in a farming operation. Most economic decisions both for crop and animal enterprises are made in terms of how to use each specific field in the farming operation. Because of this, most producers also consider a "field" as the basic unit of a rotation system. Since most fields in Kentucky are extremely variable in size, this often makes it difficult to design a rotation system which will provide uniform crop production acreage on a long-term basis. Despite this shortcoming, most cropland rotation in Kentucky is presently accomplished by rotating "fields."
Perhaps a better unit of rotation would be strips within fields. However, problems encountered during past years in establishing strips along the natural contour of the field have resulted in their not being extensively used. By using no-tillage planting and other applicable conservation practices, however, many sloping fields can now be laid out in parallel strips of uniform width without concern for excessive erosion. Such fields can easily accommodate large equipment. While use of such residue management practices as no-till planting and chisel plowing make it possible to use parallel strips which do not uniformly follow the natural slope contour, forethought is necessary in establishing the strips in order to most efficiently use a field. The USDA-SCS provides technical help through their local district offices for laying out fields into strips. It is important to lay out strips wide enough to justify using large equipment, yet narrow enough to justify using the strips as a conservation practice. Practical experience indicates that strips should probably be no less than 25 feet wide or no greater than 75 feet wide, depending on steepness. In any case, the actual width should conform to some even multiple of planter width to be used.
Rotation in this system is between strips. Each strip in this sense becomes a "field." The "strip" rotation system, when combined with no-till planting and sod waterways where needed, is particularly advantageous in intensifying rowcrop production on land tracts with erosion hazards, while providing good soil erosion control.

Systems of Cropland Rotation
Tobacco-Sod Rotation - Tobacco is by far the single most important row crop grown in Kentucky, even though in any given year only about 200,000 acres are required to produce the allotment. Because of this economic importance, tobacco should always be grown on the most suitable land available to a producer. Although erosion hazard on land used for tobacco is minimal on most farm tracts, rotation of tobacco with a sod-forming crop is still a desirable production practice. A system of two years continuous tobacco followed by two years of a perennial sod crop provides fewer soilborne disease problems and better maintenance of soil "tilth," to which tobacco responds. Additionally, less nitrogen is required for tobacco following plow-down of a good sod. Red clover, tall fescue, orchard grass or timothy are all perennial forage species which, either seeded alone or as a red clover-grass mixture, provide excellent hay production during the sod part of the rotation; they then provide an excellent sod to plow under for tobacco production. This system works extremely well in fields laid off in strips rotated between tobacco and hay every two years. In this system, the cropping rotation would be:

One full cycle of the rotation
year 1-tobacco (followed by winter cover crop)
year 2-tobacco (followed by clover-grass hay)
year 3-clover-grass hay
year 4-clover-grass hay

Then, for year 5, rotate back to tobacco.
Corn-Soybean Rotation - This has become a fairly common rotation in some parts of Kentucky, particularly where fields are Johsongrass-free or where Johsongrass can be controlled. It is often combined with the "double-cropping" of wheat or barley with soybeans to provide for three acres of grain production on 2 acres of land every two years. Following corn harvest, wheat or barley is seeded. Following small grain harvest, soybeans are immediately no-till planted into the small grain stubble. This rotation is completed by growing corn following the soybean crop. Beyond the capability for double-cropping small grain and soybeans in this rotation, there are also the important advantages of (1) better corn production following soybeans and better soybean production following corn as compared to continuous culture of either, (2) better broad-spectrum weed control (chemical treatments for Johsongrass control are generally more practical with soybeans than with corn), and (3) better control of soil-borne insects and diseases. (This rotation will become increasingly more important in controlling the soybean cyst nematode.)
Use of this rotation in "strips" through fields provides a unique advantage to producers. In the "strip-rotation" of corn and soybeans, much land with moderate to severe erosion hazard can be used intensively for continuous row-crop production of corn and soybeans because of the inherent conservation aspects of the rotation. Strip cropping, no-till planting and winter ground cover, when used with establishment and maintenance of sod waterways, minimize erosion hazards on moderately sloping fields. The University of Kentucky College of Agriculture conducted a 4-year study of this system on a 6-12 percent sloping, moderately eroded Christian silt loam soil. Results from this study are shown in Table 3. Wheat yields were 25-30 bushels per acre on the double-cropped strip. In this "strip-rotation" system of corn and soybeans, the cropping sequence would be as shown on the top of page 4.

Table 3. Yield of Corn and Double-Cropped Soybeans Grown in a Strip-Rotation

Crop1	1977	1978	1979	1980	4-Yr Average
Corn	152	138	154	136	145
Soybeans	59	47	50	33	47

¹ Study was initiated in 1977 in a dense tall fescue sod. Both crops were fertilized sufficiently with P₂O₅ and K₂O. Corn was fertilized with N at the rate of 150 lbs/A/yr. Average planting date for soybeans was June 22.

By growing corn and soybeans in alternate parallel strips using no-till planting, winter cover, double-cropping, and maintaining sod waterways, no undue soil erosion had occurred after 4 years of continuous production on this sloping hillside that has a severe erosion potential.
This system is also amenable to producers with silage-requiring livestock operations. In this case, small grain following the soybeans could be chopped for silage near mid-May, making it possible to plant full-season double-crop soybeans. The corn strips would be chopped for silage or harvested for grain in whatever proportion necessary for a specific feeding operation.
This system can be modified for grain production to produce full-season soybeans and requires that only half the acreage be seeded to a winter cover crop. The modified version would also consist of corn and soybeans being grown on alternate parallel strips. However, small grain would be seeded only on strips from which soybeans were harvested. Rye is probably the best small grain species to use in this system, since the purpose of the small grain following soybeans is to provide additional overwinter cover to the sparse residue from the soybeans and to provide a mulch for no-till planting of corn the following spring. On the strips from which corn is harvested, no cover crop would be planted since there is sufficient residue left behind the combine to adequately protect the soil over winter. These strips would be chisel-plowed the following spring and used for planting full-season soybeans. The advantage of this modified strip system would be the higher yields normally obtained from full-season soybeans, and the lesser expense and time in seeding a winter cover crop. Additionally, each strip would be deep-plowed in alternate years, loosening any traffic-caused soil compaction.

Year	Strip 1	Strip 2
1	corn; fall seeded small grain	soybeans; fall seeded small grain
2	harvest small grain; plant no-till double-crop soybeans; fall seeded small grain	no-till corn into small grain; fall seeded small grain
3	no-till corn into small grain; fall seeded small grain	harvest small grain; plant no-till double-crop soybeans; fall seeded small grain

Grain sorghum can be substituted for soybeans in this alternate strip rotation and produced either as a full-season crop or double-cropped.

Corn-Red Clover Rotation - This rotation is of particular advantage on strongly sloping fields. It is a "short-term" rotation based on full utilization of the normally expected two-year life of a red clover stand. It requires three units among which to rotate, either fields or strips within fields. A 3-year version of this rotation would occur in sequence as follows:
 

Year	Crop Sequence
1	no-till corn; fall-seeded small grain
2	overseed small grain with red clover in late winter; harvest small grain as silage or grain; take 2-3 cuttings of red clover
3	take 3-4 cuttings of red clover
4	rotate back to no-till corn

After 3 years, this rotation can be completely established either on 3 separate fields or among 3 alternately occurring strips within any field. By no-till planting the corn, the only open soil in this rotation is the one-third of the acreage seeded to small grain following corn during mid-September to mid-November. For this reason, erosion risk is low. When the rotation has been fully established, each acre produces one-third acre of corn (for silage or grain), one-third acre of small grain (for silage or grain), one-third acre of first-year red clover, and one-third acre of second-year red clover. It provides an additional advantage of always planting corn into a red clover sod, which requires substantially less nitrogen fertilizer for top corn yields as compared with continuous corn monoculture.
This system has been tested by the University of Kentucky College of Agriculture in eastern Kentucky on a 12-20 percent sloping Allegheny loam soil with severe erosion hazard. Results are shown in Table 4. During the three years of this study each acre in rotation produced an average of about 57 bushels of corn, 27 bushels barley, and 2 tons red clover hay. For silage, the yields were 8.8 tons corn silage and 2.5 tons barley silage.

Table 4. Yields of Corn, Barley and Red Clover Grown in a Strip-Rotation

Crop	Year
	1	2	3	Av.
Corn (grain yield, bu/A)	178	156	175	170
Corn (silage yield, T/A)1	28.7	26.7	24.2	26.5
Barley(grain yield, bu/A)	57	53	---	55
Barley (silage yield, T/A)1	6.2	7.1	9.3	7.5
Red Clover (hay yield, T/A)	3.22	2.82	2.82	3.0

¹ Silage yields at 35% dry matter content

Another version of the corn-red clover rotation can be accomplished by growing corn in the same field or strip for two consecutive years before rotating to red clover. This 2-year rotation makes it possible to grow more total corn per unit of area used than in the 3-year rotation and is more suitable to fields with a less severe erosion hazard. Two units are required for this rotation, either two fields or two alternate strips within a field. In this case, following harvest of first-year corn, a small grain is seeded to provide winter cover for use as silage or mulch the following year into which second-year corn would be no-till planted. After harvest of the second year corn, small grain would be fall-seeded, and red clover would be overseeded to provide for two years red clover production before rotating back to no-till corn.
Corn-Alfalfa Rotation - This rotation, while of longer duration because of the longer life of an alfalfa stand, is useful because of the high yields of high quality forage produced. These high forage yields, when combined with the corn, will provide much of the nutritive requirements for a dairy herd or other intensively fed livestock enterprises. Two rotational units are required -either two fields or two alternate strips within a field. The perennial nature of the alfalfa provides good erosion control for the life of the stand, while corn, particularly if no-tilled, can be grown continuously for an expected 4 to 5 years before rotation with the alfalfa. While entire fields can be rotated in this manner, greater erosion protection on steeper sloping fields can be obtained by growing the corn and alfalfa in alternate parallel strips. It is important for erosion control to either fall seed a small grain each year following corn for use as either silage or mulch for no-till corn planting, or to leave corn residues on the ground over winter before preparing a corn seedbed the following spring. With this rotation, each acre would produce a half-acre of corn and a half-acre of alfalfa. If a small grain such as wheat is used for winter cover following corn, it is possible to chop it for silage by mid-May, and no-till corn into the stubble, thereby harvesting a half-acre of corn, a half-acre of small grain, and a half-acre of alfalfa from each acre in the rotation.