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Oklahoma State University Stillwater, OK |
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Oklahoma Alfalfa |
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Oklahoma State University Stillwater, OK |
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Oklahoma Alfalfa |
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KEYS TO ALFALFA
STAND ESTABLISHMENT It is time to begin thinking and acting if you may establish a new alfalfa stand this fall. With all the rain we have had lately, we can see where water stands in fields. Take note of these areas, and work out a drainage system before planting a new stand of alfalfa in the fall. This is the time to begin steps toward three keys to stand establishment as discussed below.
Stand productivity and longevity are best on deep, fertile, well-drained loamy or sandy loam soils. Productive alfalfa stands require soils with adequate infiltration, yet sufficient clay and organic matter to hold moisture. Soil with good water-holding capacity is important because high alfalfa yields require large quantities of water (approx. 6" of available water for each ton of hay). Alfalfa roots can penetrate 25 ft. in deep soils, and high yield and long stand life are attainable in sub-irrigated fields -- those with a water table between 5 ft. and 20 ft. deep. If, however, the water table rises to the surface during warm seasons, alfalfa grows poorly and may even die within a few days from "scald." "Scald" often kills alfalfa plants when water stands during bright sunny days. Oxygen is not available to roots and the water holds in heat. Scald usually occurs in thin stands or just after harvest when foliage does not shade the soil. Scald differs from root rot in that there is no pathogen involvement and no genetic resistance is available. Waterlogged soils have poor aeration, inhibit nitrogen fixation, and encourage certain root rot diseases. Much alfalfa in the state grows along creek and river bottoms that do not flood for prolonged periods of time. These alluvial soils are usually deep, drainage can be provided, and fertility problems (if they exist) can be corrected profitably. Avoid using sites that may have herbicide carry-over problems. Alfalfa is very sensitive to picloram (sold as Grazon PC and Tordon 22K) and some of the new sulfonylurea-urea herbicides such as Ally, Glean, and Amber. Alfalfa is usually not listed as a rotational crop for these herbicides. When it is listed, there is a 22 to 34 month minimum rotational interval before alfalfa can be planted. Also, field bioassay with alfalfa must be performed after application of some of these herbicides before alfalfa can be legally planted.
Commonly overlooked steps in alfalfa production include developing and maintaining proper soil fertility. Nutrient deficiencies and pH (acidity) should be adjusted before preliminary seedbed preparations. Once a site is selected, soil sampling and analysis should occur well in advance of sowing. A year in advance is a good idea. Alfalfa is a heavy user of phosphorus, calcium, and potassium. A 5-ton/A hay harvest removes approximately 75 lb/A of P205, 100 lb/A of calcium, and 300 lb/A of potash. In some soils, these quantities are readily available; however, in others, much of this must be applied. For best results, both lime and fertilizer should be incorporated into the upper 6" of soil before stand establishment, then monitored by soil testing every year. If essential nutrients become deficient, or if the soil becomes excessively acidic, yields decrease and the alfalfa stand life will be shortened. Problems with weeds increase on nutrient deficient soils because of reduced alfalfa competitiveness. Herbicides can control weeds, but alfalfa yields will still be low due to soil fertility problems. Lime and phosphate fertilizer are relatively slow to improve soil productivity. If large amounts are required to bring the pH and phosphorous to acceptable levels, they should be applied and incorporated 6 months to 1 year prior to sowing alfalfa. Before sowing, apply enough lime to neutralize the soil and enough phosphorous to satisfy the crop's needs for 3 years. Annual applications of potassium are recommended for deficient soils. The cost of Lime and Fertilizer may seem high, but cutting corners on these important factors leaves the other activities in jeopardy. An inexpensive soil test can save producers money by indicating which nutrients are deficient and what quantity should be supplied. This may help avoid the cost of unnecessary fertilizer. If soil analyses indicate the need for more fertilizer and lime than is affordable, one should consider another site. Building up the fertility and pH over several years may be recommended.
Assuring good surface drainage is critical before establishing alfalfa. General land leveling to remove improperly placed dead-furrows and back-furrows should be done several months, or a year, prior to sowing alfalfa. Development of a well-drained field frequently requires several attempts. One of the best indicators of drainage problems is standing water between rains. Seedbed preparation begins with the removal of the previous crop and involves many possible combinations of farming equipment. Generally, the normal steps include primary tillage, disking, leveling, and smoothing. Primary tillage consists of moldboard plowing, chisel plowing or deep disking. Many producers believe that plowing at least 8" deep is essential to bury crop residue and control weeds by burying growing plants and nongerminated seeds. However, O.S.U. researchers have found that deep disking can be used as a substitute for moldboard or chisel plowing. In soils that develop hardpans, a chisel plow is commonly used to rip through existing hardpan layers. Shallow disking normally follows primary tillage. Disking
breaks up the clods and is a good tool for incorporating residue, lime, and fertilizer.
Sometimes disking several times may be required, depending upon the soil condition.
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| John Caddel, Forage Agronomist Department of Plant and Soil Sciences Oklahoma State University |
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#1. Site Selection. A
weed-free field with deep, fertile, well-drained soil produces high yields and facilitates
long stand life. 
#2. Soil Test. Apply
fertilizer and lime according to a reliable soil analysis. Phosphorus and lime should be
applied several months prior to planting. 
#3. Land Preparation.
Level field and drain low areas, well before sowing.