Selecting the Right Soils for Top Alfalfa Production

Warren C. Thompson
National Forage Specialist: America’s Alfalfa

Alfalfa is a perennial legume. Once seeded, the plants regenerate growth from a crown and root system rather than depending on seed for continued production. As a legume, it is able to produce it’s own source of nitrogen for growth. In addition to the production of nitrogen for it’s own growth, it accumulates residual nitrogen for use by subsequent crops and for use by non-nitrogen producing plants such as grasses when they are grown together.  

It has a vigorous taproot that has been known to grow 30 feet deep. Road builders, when cutting a new road through an old alfalfa field many years ago in Kansas, found alfalfa roots to 30 feet deep and beyond. I have traced alfalfa roots in the loess soils of the Eastern Coastal plains and the lower-mid plains states to 6-7 feet deep in new road cuts. 

Does this mean that the only soils that are ‘fit’ to grow alfalfa should be that deep? Of course not but the fact remains that the deeper the soil is to an obstruction such as solid rock or a hardpan, the better the chance it will endure and produce well. Soil color is not always the total answer but it is a start. A brown to red or black soil that is not subject to flooding and/or retaining surface water for rather long periods is a step in the right direction. 

I have also seen alfalfa die in two years or even less when it was seeded on wet-natured soils that do not drain well internally. I have seen one, two, three year old stands “heave or “spew” out of the ground in the early springtime after a period of frequent freeze-thaw conditions on these soils. If you want top yields and persistence, seed your alfalfa on soils that are well drained internally. 

The best way to determine soil quality and adaptability to alfalfa is a soils map. These maps are usually available in every county in the USA. If you don’t have a soils map, call and talk with your County Agent or your local NRCS technician to see what it takes to get this done and do it! While you are talking with your County Agent, ask him about soil testing and go ahead and get that done well before planting to direct you to the current and long time needs for lime and fertilizer needs.