AGR-98 
STRIP CROPPING AND CONTOURING
ISSUED: 8-83
REVISED:
K.L. Wells
Department of Agronomy

The risk of erosion is the most commonly encountered hazard in the use of Kentucky's farmlands for agricultural production. On a statewide basis, about 75 percent (11.4 million acres) of the 15 million acres of land suitable for producing row crops, hay and meadow crops, or permanent pasture crops has some degree of erosion risk.
Although the degree of erosion risk varies within the state, most Kentucky farmers have at least one field where there is need for cropping systems and cultural practices to help reduce erosion. To determine what production system is best, each sloping field should be evaluated for soil characteristics and erosion loss potential. On this basis, the need for specific erosion control practices can be identified which will enable the field to be used to its maximum agricultural potential. Two crop production practices that can be used to reduce erosion are strip cropping and contouring.

Strip Cropping
Producing crops in strips running across the slope can greatly reduce the risk of erosion by cutting surface water runoff approximately in half. Using strips effectively shortens the slope length, thereby slowing runoff of surface water from sloping fields. Adding sod waterways in natural channels on hillsides and using no-till techniques to plant crops into the strips should almost eliminate the erosion problem.
This approach to erosion control has particular advantage since: 1 ) no additional production costs are involved, and 2) it enables a more intensive use of sloping fields.

Evaluating Fields for Strip Cropping
Each field should be evaluated to determine three factors:
1)Which crops can suitably be grown on the field's soils--This largely depends on the depth of the rooting zone. If there are 36 to 42 inches through which roots can grow, any crop climatically adapted to an area should grow well. If presence of such features as a fragipan, clay layer, bedrock or high water table occurs at depths shallower than 36 to 42 inches, then crop selection and cropping systems should be developed to minimize the potential effect of these features on crop production.
2)The most effective surface water management system for the field-gully erosion can be prevented by establishing sod-based waterways in the naturally-occurring major drainage channels running down slopes of the field. Using practices such as surface residue management, minimum tillage or no-till, winter cover crops, and crop rotations, in addition to establishing strips, will reduce the risk of rill and sheet erosion.
3)The specifications for strips to be used on the field--The USDA-Soil Conservation Service (SCS) can provide technical help in laying out strips to keep them of constant width, yet somewhat along the field contour. Strip width will largely be determined by degree of slope and cropping system to be followed, but is not likely to be narrower than 25 feet nor wider than 75 feet. In all cases, width should be some multiple of planting equipment to be used. Enough space (40 to 50 feet) must be left on each end of each strip to enable machinery to turn. This border on each end of the field should be in a continuous perennial sod. Production from these areas, as well as from sod waterways, can be obtained by cutting and baling hay.

Some fields, notably in the Pennyroyal area of Kentucky, may have such variable slope that it is not possible to follow slope contours. In such cases, straight parallel strips of constant width will still provide a good measure of erosion control, particularly if no-till planting is used and crops are rotated among the strips.

Establishing Cropping Systems in Strips
Each strip should be viewed as a small, individual field, since many management decisions will be made on each strip or on groups of strips. Which crop rotation to use is probably the most basic of these decisions, since strip cropping will most likely involve growing at least two crops in some form of rotation among the strips. Although there are numerous possibilities for cropping systems, the following ones are the most common:

tobacco - sod (legume and/or grass)
corn - soybean (either full-season or double-crop soybeans)
corn - red clover
corn - alfalfa

Tobacco-Sod Rotation--Rotation of tobacco with a sod-forming crop is a desirable production practice. A system of two years continuous tobacco followed by two years of a perennial sod crop provides fewer soil-borne 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 that, either seeded alone or as a red clover-grass mixture, provide excellent hay production during the sod part of the rotation. They also 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, one full cycle of the rotation in each strip would be:

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. By initially planting tobacco in alternate strips, the sod crop also exists in alternate strips.

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 each acre of land every two years.
This rotation used in "strips" provides a unique advantage to producers since its inherent conservation aspects allow much land with moderate to severe erosion hazard to be used intensively for continuous corn and soybean production. This particularly is true when used with no-till planting or other surface residue management practices.
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. It allows intensive use of land by double-cropping. When crops are rotated: 1 ) production is usually improved as compared to continuous culture of either, 2) there is better broad-spectrum weed control (chemical treatments for Johsongrass control are generally more practical with soybeans than with corn), and 3) there is better control of soil-borne insects and diseases. (This rotation can be helpful in controlling the soybean cyst nematode.)
This system also works well for 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. Following harvest of corn silage, fields should be seeded to a winter cover crop.
A modification of this system to allow full-season production of soybeans would 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 for this system, since the purpose of following soybeans with small grain is to provide additional overwinter cover to the sparse soybean residue 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. Corn strips would be chisel-plowed or disked 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 and incorporating surface-applied lime and fertilizer deeper into the rooting zone.
Grain sorghum can be substituted for soybeans in this alternate strip rotation and produced either as a full-season crop or double-cropped.
The sequence of strips for the corn-soybean rotation would be:

Strip 1

Year 1--no-till corn: winter cover crop or winter fallow with residues on surface
Year 2--soybeans: winter cover crop

Strip 2

Year 1--soybeans: winter cover crop
Year 2--no-till corn: winter cover crop or winter fallow with residues on surface

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 can be established in alternate strips by growing two continuous years of no-till corn followed by two continuous years of red clover. Or, if more forage is desired, it can be established as a rotation among three strips (two clover and one corn). The sequence for each strip of this three-year rotation would be:

Year 1 --no-till corn followed by a winter cover crop of small grain
Year 2--overseed the small grain in late winter with red clover, harvest the small grain as silage or grain, then make two to three cuttings of red clover
Year 3--take three to four cuttings of red clover
Year 4--rotate back to no-till corn

After getting the rotation fully established in units of three strips, there would be one strip of corn, one strip of first year red clover, and one strip of second year red clover occurring in sequence down the hillside.

Corn-Alfalfa Rotation--This rotation, though longer 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. The rotation is set up in units of two strips. Alfalfa is grown in alternate strips with no-till corn for as long as satisfactory stands exist, at which time no-till corn is rotated onto the alfalfa strip. No-till corn is grown continuously in alternate strips either into residues from the previous year or into small grain seeded to provide winter cover.

Maintenance of Strips
Once strips are established, care should be taken to maintain them in constant width to prevent formation of point rows and over-planting onto an adjoining strip that may contain a different herbicide. If desired, a strip off fescue sod just wide enough to mow, can be established and maintained between each strip. Though lowering the total planted acreage, these fescue "filter" strips can provide protection on strongly sloping fields from slopewash of herbicides onto adjoining strips. It is also very important to use herbicides or herbicide mixtures that will not cause enough residual carry-over to damage the succeeding crop to be grown in each strip. One of the most common problems encountered in strip cropping is maintenance of sod waterways. Care must be taken when applying herbicides to cut spray nozzles or spreaders off each time you go across a waterway. Otherwise, sod will likely be killed and have to be reestablished.

Contouring
Tilling and planting along slope contours are effective methods in slowing surface water runoff and reducing erosion. Effectiveness can be increased even more by using tillage methods that leave at least some previous crop residues on the surface. A combination of no-till and contour planting is perhaps the most effective system to use in minimizing surface water runoff from sloping fields. And when these two practices are incorporated into strip cropping and rotations, much sloping land can be more intensively used for crop production with good erosion control.
The greatest limitation to contour planting and tillage is in fields with short, narrow slopes that break in more than one direction. Planting on the contour in such fields results in a great number of "point" rows that are a hindrance in field operations. The best erosion control on such unevenly sloping fields comes with no-till planting.