Alfalfa – Spring Management

As fields finally start to dry out, and warmer temps seem to be finally sticking around, the alfalfa in the area will really start to take off soon. Below are some management tips for the upcoming spring season.

Herbicides and Weed Management
With such wet conditions so far this season, many fields may not have gotten sprayed with the herbicide products we normally apply during winter dormancy. There is still time to apply these products, but it may result in a yellow flash on the alfalfa. This should not cause any long-term affect. Applying residual product will help keep your first cutting clean of weeds. After the first cutting, the thickness of your stand and ground cover will help shade out more flushes of weeds.

Nutrient Management
Alfalfa fertilization is not a commonly discussed topic; yet is very important in continuing to pull high quality, high tonnage yields. Soil tests can be used to determine the needs of your field. The nutrient removal chart below shows approximately how much fertilizer is removed with each ton of alfalfa. Based on nutrient removal and results of soil tests, apply adequate fertilizer to supply nutrition for this crop and consider working on building your soil test levels as well. Tissue tests are another valuable tool in alfalfa nutrition management. Samples are typically pulled shortly before the cutting, utilizing the top 4-5 inches of the plant. This test will help you understand what you will need to apply for the next cutting, or at least get a snapshot of how you are doing on fertility.

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When pulling a soil sample, be sure to test for Soil pH.  Nutrient availability and plant health can be affected by pH. Alfalfa is especially sensitive to soil pH levels, with a pH of 6 or above being recommended.

Reading the Stand
Another important piece of alfalfa management is understanding the health of the stand in your field. This will help you determine how soon you should terminate the stand and rotate out of alfalfa. As noted above, a healthy stand is key in keeping weed pressure down as well as for the best possible yields. The stand should be read in the spring and fall, using number of crowns per square foot as your measurement.
Winterkill can cause thinning in the stand. To determine if you are seeing winterkill or another kind of crown rot, look at the color of the crown when cut in two. Dig multiple plants throughout the field and cut the crowns. An ugly yellow-orange color typically indicates winterkill, while crown rots are more brown in color.
Using satellite imagery, such as that from WinField United’s R7 Tool®, can help locate areas to check when you are at the field. Look for visual differences in the imagery then compare the better and worse parts of the fields when walking to see what may be causing the differences. It may be winterkill, weed pressure, or even insect damage.

Insect Control
Alfalfa weevil larvae can do major damage to your first cutting of alfalfa if not monitored and treated in a timely manner. Start scouting for alfalfa weevil larvae as soon as we start to see some greening up or new growth in the field. 1-2 Larvae per stem can cause enough economic damage to justify treatment. Last season, very few fields in the area were treated for alfalfa weevil, however this is very atypical for our area. Scouting should be done at least weekly, and more often when starting to find weevil larvae in the field.

Cutting Schedule
Traditional approach to taking the first cutting of alfalfa has been to wait until at least 10% bloom. Another, potentially better, option would be to take the cutting when the alfalfa reaches a certain height OR when you start to see regrowth at the crown. If you wait until 10% bloom, this regrowth may be cut at the same time, thus slowing the regrowth of the next cutting.

Utilizing these tips and ideas, have a safe and productive spring season.