Alfalfa is typically used as a natural fertilizer for other crops. The plant helps to add high amounts of nitrogen to the soil. As a crop itself, it can remove many nutrients from the soil. Potassium, zinc, sulfur and boron deficiencies are most common in alfalfa plants. Deficiencies can reduce the yield, disease resistance and hardiness of alfalfa plants. Use liquid fertilizer both on soil and on foliage to supplement the fertilizing requirements of alfalfa.
Dig to a depth of 3 inches in one corner of your alfalfa garden and fill three clean containers with 1 cup of soil from this location. Label each bowl with the location you obtained the soil from in the garden. Write "Nitrogen" on the first label, "Potassium" on the second and "Phosphorus" on the third.
Mix each of the three samples with 5 cups of water. Open one pill for the nitrogen test over the bowl labeled "Nitrogen" and mix the contents of the pill into the solution until it is well blended. Repeat the process for the potassium and phosphorus soil samples, then let each solution settle for 30 minutes.
Fill the nitrogen test compartment with solution from the container labeled "Nitrogen," using the dropper provided with the test kit. Fill the potassium and phosphorus test compartments with solution from the appropriate containers in the same way. Wait 10 minutes for the colors of the solutions to change.
Compare the results with the chart that came with your kit to determine if the soil around your alfalfa needs to be fertilized. Pay special attention to whether the potassium level of your soil is getting low around your plants.
Clean the test compartments and repeat the tests for other locations in your garden to see if nutrient levels change in different areas of soil.
Mix 1 pint of liquid fertilizer with 2 gallons of water for every acre of alfalfa you are growing. Apply the fertilizer mixture to the soil around your plants with a hose end sprayer.
Dilute your fertilizer mixture to half-strength and use the hose end sprayer to mist the solution over the leaves of your plants as foliar fertilizer.