By Dr. Harold Willis
The best seedbed for forage establishment is firm and moist. Firmness will prevent loss of essential moisture; however, a crust is very detrimental to seedling emergence. Good tilth and humus content will prevent crusting. Fall plowing and spring disking and harrowing work well in most areas; however, fall plowing is not recommended in areas where erosion could be increased (steep slopes and high rainfall). Optimal seeding depth for legumes and grasses is less than one inch. In fine-textured and moist soils, seeds should be planted closer to the surface, from 1/2 to 1/4 inch. In summer or drier periods or in sandy soils, deeper planting (¾ to 1 inch) is recommended. Since shallow seed placement is necessary for good emergence, the use of a corrugated roller or packer will provide firmness. The key here is to create firm soil and not compacted soil.
Compaction from use of heavy farm machinery is a contributing factor to anaerobic soil. Reducing or eliminating toxic chemicals and increasing humus content will alleviate these problems, but if your soil is so tight and “dead” that organic matter will not decompose quickly to form humus, then you can break out of this vicious circle by use of a soil conditioner to loosen soil and stimulate soil life. Depending on your soil’s needs, some rock fertilizers can help condition soil (calcitic lime and soft rock or colloidal phosphate) or some commercial soil conditioners can be beneficial (although some kinds are not so helpful or can even do long-range harm). Inoculating the soil with beneficial bacteria and other organisms may help (if the soil conditions are already fairly good, and not toxic).
A stubborn hardpan can be broken up by subsoiling or by plowing a little deeper each year, but a good earthworm population can do a better and quicker job of it.
The mineral elements that are most essential for good stand establishment are calcium (Ca), phosphorus (P), and potassium (K). Calcium is needed for cell division, cell wall formation, and root growth. Phosphorus is used for energy transfer and other metabolic functions in the plant, and also it increases root growth. Adequate phosphorus is especially critical for stand establishment. Potassium is required to activate many cell enzymes and for food transport in the plant.
It is impossible to give definite recommendations regarding fertilizers without knowing what your soil needs, but the soil should have a high level of available calcium and phosphorus. If your soil needs these elements, good sources are calcite lime plus soft rock phosphate. These plus an application of organic matter (6 to 10 tons/acre of fresh cattle manure, or 1/2 to 1/3 that amount of poultry manure, or 1 to 3 tons/acre of compost) will take care of most nutrient needs of alfalfa and other forages. The organic matter will provide enough potassium as long as calcium and phosphorus are high. Fresh organic matter should not be applied in excess nor be plowed in too deeply (below 5 to 8 inches) because it may not decompose properly, but may putrify and release toxins. It should be worked into the upper several inches (the aerobic zone).
Standard recommendations state that alfalfa should have a soil pH of 6.5 to 7 or 7.5, which is above the average for most crops. Actually, not so much attention should be paid to the exact pH figure because (1) the pH of soil changes constantly, even from day to day, and (2) the pH readings produced by a soil testing lab depend on the methods used. For example, if the soil samples are finely ground before testing, the pH readings will be somewhat higher than under field conditions because small lumps of lime will be ground up and made more available.
Perhaps one reason a higher pH is recommended for alfalfa is that alfalfa requires high levels of calcium, and large amounts of lime are applied to raise pH, automatically supplying the crop’s need for calcium. Low pH (below 6.0) can have detrimental effects in reducing or eliminating growth of beneficial soil bacteria, including nitrogen-fixing bacteria, but high quality forage can be grown on acid soil, provided it has balanced and high fertility. Remember: balanced soil is the key to quality forage.
Source: How to Grow Great Alfalfa