Now that the wheat has been harvested and second cutting of hay completed, it is time to prepare for next year's alfalfa crop. August gives growers an opportunity to establish alfalfa fields, provided there is sufficient soil moisture for seed germination and plant emergence. With the uncertainty of next year's water supply, many farmers are taking advantage of this year's water allotment to establish new alfalfa stands.
Summer plantings are the norm for elevations around 5,000 feet. Even in the lower valleys, planting during the warm summer months offers advantages. Warm temperatures promote rapid and uniform emergence and development of the young seedlings, and the danger of a killing frost is very low. The broadleaf herbicide 2,4-DB works well under these conditions. The major disadvantage of summer planting is that hot dry weather in midsummer can make maintaining adequate soil moisture extremely difficult, and make frequent irrigation necessary. An inadequate irrigation system or insufficient labor is an insurmountable obstacle to summer planting.
Alfalfa can be seeded into moist soils or seeded into dry soils and then irrigated. Planting into moisture can be accomplished by either pre-irrigating before planting or by preparing the seedbed in the fall and taking advantage of winter precipitation to provide moisture. The advantages of planting into moist soils are that the moisture has usually melted the clods and, if the moisture is uniform, alfalfa seeds can germinate uniformly and quickly. Also, keeping up with irrigation is easier when starting with a full soil-water reservoir. Contact-type herbicides or shallow cultivation can be used to control weeds that emerge prior to planting. Despite these advantages, the time required for seedbed preparation, irrigation, surface drying, spraying for weed control, and then planting deters many growers from pre-irrigation. Preparing the seedbed, planting, and irrigating is much simpler. However, a dry planting system can be less forgiving. The grower must take great care to meet the water requirements of the young crop. Weed populations are usually higher in fields that have not been pre-irrigated, making post-emergence weed control more difficult.
Adequately fertile soil is fundamental to successful stand establishment. Soil fertility contributes to seedling vigor, which helps alfalfa compete with weeds. Analyze soil fertility prior to planting; pH should be in the range of 6.2-7.5, the nutrients that are most commonly needed are sulfur, followed closely by phosphorus, then potassium, boron, and molybdenum. If soil is deficient in phosphorus (marginal levels are between 5-10 ppm), apply a 1- to 2-year supply at planting. Critical soil potassium levels are between 40-80 ppm.
Finally, keep in mind that any time alfalfa is planted the following factors must be managed:
• Seed selection: Be sure to use high quality seed of adapted, tested varieties and use fresh inoculum of the proper Rhizobium bacteria.
• To compensate for less than-ideal conditions and unforeseen weather, the seeding rate recommended for irrigated fields is 15 to 20 pounds per acre when drilling and 20 to 25 pounds per acre when broadcasting.
• Planter calibration: If a coated alfalfa seed is used, be aware that coatings can account for up to one-third of the weight of the seed. This can affect the number of seeds planted if the planter is set to plant seed on a weight basis. Seed coatings can also dramatically alter how the seed flows through the drill, so be sure to calibrate the drill or planter with the seed being planted.
• Also, remember that seed placement is critical. More stand establishment failures probably relate to seeding too deep than to any other single factor. Seeding depth should not exceed 3⁄8 inch, except for sandy soils, where 5⁄8 inch is acceptable. Seeding deeper than this can reduce seedling emergence considerably.
Everyone should be aware that without alfalfa hay, we would not have meat, milk, butter, ice cream and other dairy products when we go to the grocery store. So, as a popular bumper sticker reads, "If you have ate today... Thank a farmer".
Source: "Intermountain Alfalfa Management", University of California, Publication 3366.
[[In-content Ad]]
