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Plant Alfalfa in August

Plant Alfalfa in Fall, Nebraska Extension Acreage Insights for August 17, 2018,

Alfalfa can produce more protein per acre than any other crop in Nebraska. Up to 100 percent of the protein needs of most livestock can be supplied by alfalfa in addition to large amounts of vitamins, minerals, and energy.

Besides being an excellent livestock feed, alfalfa improves the soil by adding nitrogen and organic matter, increasing water infiltration, improving soil structure, and providing excellent erosion control. All these attributes make alfalfa a highly desirable crop for many farms and ranches.

Follow proper seeding techniques when establishing alfalfa stands. Poor seeding management will decrease chances of developing a productive alfalfa stand. High yields of good quality forage can result only from well-established, properly managed, productive stands of alfalfa.

Select a Suitable Soil
Alfalfa thrives on deep, well-drained loam, silt loam, silty clay loam, or clay loam soils with a pH between 6.2 and 7.5. Sandy soils can produce excellent alfalfa yields when properly fertilized and irrigated. Avoid poorly drained soils or those with high water tables because alfalfa will not survive in soils with prolonged watterlogged conditions. Alfalfa is also poorly suited for saline or shallow soils.

Alfalfa can be seeded either in spring or fall in eastern Nebraska. Whether it is best to plant alfalfa in the spring or fall depends on two factors, predominant weed species and soil moisture. If the predominant weed species are summer annuals such as foxtail and pigweed, it may be best to plant alfalfa in the fall IF the soil profile has adequate moisture for germination and growth. This allows the alfalfa to get established with less weed competition. When established in the fall, alfalfa greens up in early spring and will get a head start on annual weeds next spring that must come from seed when the soil temperature and moisture is right for germination.

If the predominant weed species are winter annuals such as pennycress or downy brome, spring planting may be best. The weeds can be killed with tillage or herbicides in early spring and then the alfalfa planted into a clean seed bed. Pennycress, downy brome, and other winter annual weeds are more predominant in former wheat or oat ground because they have the same growth habit as winter wheat.

The best time for fall seeding alfalfa in eastern Nebraska is in late August, provided adequate soil moisture is available. Farmers sometimes wait until mid- to late September to plant alfalfa. This is most often too late because the plants do not have a chance to become established before a first killing frost and they are more susceptible to winterkill.

Ideally, the latest alfalfa should be seeded at least six weeks before the first hard freeze (see map). Later plantings may be successful, but the chances of poor stands increase as planting is delayed later in the fall. If planting cannot be completed by the desired time in fall, it is best to wait until the following spring.

A map of Nebraska showing ideal planting times.Planting before the indicated date usually provides at least six weeks before the first hard freeze (20°)

Field Preparation
The natural tendency is to do tillage to create a fluffy, gardenlike seedbed. However, if you can’t bounce a basketball on the seedbed prior to planting alfalfa, the seed bed is too loose! If you don’t have a basketball, walk across the seedbed. If your heel sinks in more than 1⁄2 inch, it is too loose. A good rain after tillage will help firm the seedbed. Harrowing with the spikes set flat or rolling with a packer will firm seedbeds provided there is some moisture in the soil.

When seeding alfalfa, you need to remember your only chance to make a rough field smooth enough to drive over with tractors, swathers or pickups is prior to seeding. Complete tillage (disking) to smooth the surface following row crops is ok if the soil is firmed up by either rain, sprinkler irrigation, or packer-seeders. If the untilled soil surface is already smooth, no-till drills have been very successful. In fact, no-till seeding of alfalfa following small grain crops has become a trend among successful alfalfa producers.

Both lime and phosphorus do not move into the soil rapidly with rainfall and need to be incorporated with tillage. Phosphorus can also be banded in the soil at planting time. Incorporate lime, if needed, into the soil prior to seeding. If more than 2 tons of lime per acre are required, incorporate the lime at least 6 months before seeding.

Most soils in Nebraska need phosphorus to produce top yields of alfalfa. It can be broadcast and incorporated into the soil prior to seeding or it can be band applied with the seed by the drill at planting. Band application at seeding is often more effective than broadcast because it places readily available phosphorus near the roots of new alfalfa seedlings.

Alfalfa production on sandy soils often benefits from other nutrients, especially sulfur. Sulfur is most often needed where soil organic matter is less than 1 percent and irrigation water, if used, is low in sulfur. Boron may improve yields on some sandy soils. Alfalfa also uses many other mineral elements, such as zinc, copper, iron, and magnesium. However, most Nebraska soils supply adequate amounts of these minerals. No yield increase has ever occurred from adding these minor elements in Nebraska research studies.

Nitrogen fertilizer is generally not beneficial when applied to alfalfa. However, 10 to 15 pounds of nitrogen/acre applied at planting time often improves establishment on sandy soils.

Alfalfa seed needs to be planted 1⁄4 to 1⁄2 inch deep in fine textured soils and 3⁄4 inch deep in sandy soils for best germination. Regardless of seeding time, it is critical that alfalfa be planted into a firm seed bed. Alfalfa seeds must have firm contact with soil particles and soil moisture to insure rapid germination and emergence. A firm seedbed also helps prevent seed from being planted too deep. Leave just enough loose soil to cover seed after planting.

Productive alfalfa will use up over 250 pounds of nitrogen per acre per year. If the alfalfa is inoculated and the soil pH is correct, nodules will form on the roots and fix all the nitrogen required by the crop. Be sure to inoculate the alfalfa seed or buy pre-inoculated seed, especially if alfalfa has not been grown on the field in the past three years. If the seed came pre-inoculated, don’t leave the bags in the back of the pickup for long periods where the sun will heat them as this can kill some of the bacterial spores and may reduce the number of active root nodules. 

For more information, refer to Seeding Alfalfa.

The Nebraska Extension lockup

Source: NebGuide G2247, Seeding Alfalfa

Bruce Anderson, Extension Forage Specialist

Jerry Volesky, Extension Range and Forage Specialist