The first thing to do is get a soil sample to see if there are any nutrients that are limiting the growth of alfalfa. In northern parts of the country, alfalfa is very short lived, and it is suggested that it be seeded with a grass or clover that will fill in when the alfalfa dies.

If the soil nutrients are in the optimal range, you might consider no-till seeding to introduce mixed grass seed into the field. This is usually less costly than plowing and reseeding, but you do need to either apply a herbicide or control the clover and weeds until the grass becomes established.

If existing weeds are enough of a problem, you might want to consider your alternatives. You could no-till plant a grass-alfalfa mix, but you will still have the weeds and a difficult time controlling the weeds with both broadleaves as well as grasses planted in your field mix. If you prefer the grasses, you can control the broadleaf weeds you mentioned easily with chemical and cut management, knocking out all broadleaves fairly quickly. However, if you like the higher feed value of the alfalfa, you may have to reconsider continuing with the conventional reseeding process after checking through the Natural Resources Conservation Service or Cooperative Extension to see if someone locally is less expensive at reseeding. Check with your local county Cooperative Extension office also on the best alfalfa variety for your soil and climate; a good established stand is one way to control weeds. Grasses do eventually creep into alfalfa fields. Grasses are C4 plants (more efficient at utilizing sunlight energy for plant growth and development) than C3 plants such as alfalfa and many other broadleaf crops. Over time, grasses are also more competitive. Winter kill in areas, any high moisture areas or very dry areas, intensive cutting, cutting early (before 10% bloom) and the competitiveness of grass do allow grasses to creep into the field. Alfalfa seed is expensive at planting, but the stand should last from three to four years with a strong stand of alfalfa if variety choice and management are carefully considered—making the seed, over this time, not too expensive. Check further on your real field and feed needs, and, if alfalfa is your best choice on your soil and field, finally determine what weeds you can live with or how intensive you want to manage the fields.