Mark Garcia Farms
Agricultural Products Since 1895
Fertilizing Alfalfa and Grasses
Please read and believe! If you fertilize your Alfalfa without soil testing, please send a check to the American Red Cross instead of purchasing fertilizer. It will be a much more effective use of your money.
Fertilization
Nitrogen (N) – Some nitrogen (20-30 pounds per acre) is required for
establishment of seedling alfalfa. Once alfalfa seedlings form
nodules on their roots, they can fix their own nitrogen from the
atmosphere, so no more nitrogen needs to be applied during the life
of the stand. Nitrogen fixation is the result of a symbiotic
activity of alfalfa and Rhizobium bacteria. For the symbiosis to
occur, it is important that properly inoculated seed be used and
that the nitrogen-fixing bacteria become active. Response to
nitrogen fertilizer after alfalfa is established is a sign that
nitrogen-fixing bacteria are absent. A soil test can determine if
acidity is the problem, but neither acidity nor inoculation failure
can be corrected after the alfalfa is planted.
Phosphorus (P) and Potassium (K)- Harvesting five tons per acre of
alfalfa removes more then 50 pounds per acre of P2O5 and 250 pounds
per acre of K2O each year. Soils usually can supply some of these
nutrients, but phosphorus or potassium fertilizer (or both) often
needs to be applied before and during the life of the stand. The
fertility levels of P and K in sandy soil
change more rapidly under alfalfa production than with other crops.
The best way to determine how much phosphorus (P2O5) and potassium
(K2O) to apply is to test the soil. Because these nutrients (P and K) are considered immobile
in the soil, that is, they react with the soil and do not migrate
with the soil's moisture content, the most efficient way to get them
into the rooting zone is to incorporate them before planting.
Applying additional phosphorus and potassium fertilizers to the
surface of existing stands is somewhat less efficient, but it is
necessary in most fields for profitable alfalfa production.
Phosphorus (P) deficiencies are best corrected by applying and
incorporating a three year supply of fertilizer in the summer before
fall planting. Soil fertility levels should then be monitored
through soil testing, and any addition P should be added following
the second or third year of production from November to January,
before early spring growth. Best response to surface-applied P is
usually obtained in the first cutting. Good surface moisture in the
spring results in P uptake by surface roots. Starting the follow-up
applications of P in the second year also allows time for some
movement of P through soil disturbances caused by insects, cattle,
machinery, freezing, etc.
Potassium (K) deficiencies are best corrected by applying only
enough for one year because alfalfa will take up more than needed
when large amounts are available (luxury consumption). After alfalfa
is established, soil should be tested annually after the second
year, and K should be applied as needed from November to January,
before early spring growth.
New Mexico
Sunrise on the Tajo Alfalfa Fields
