A stand that thin is not much alfalfa.
One option is to go for the bromegrass, put about half the nitrogen you would for a pure bromegrass stand, going for forage. Terminate that stand, and plant a winter small grain and come back with alfalfa August/September 2009.

Put even less nitrogen out if you have a market for grass seed.

If alfalfa is important then cut what you have for hay ASAP, Terminate the stand and plant alfalfa, this fall.

You may be able to kill the stand and plant corn for this season.

Here, I probably would fallow the field till I could plant alfalfa. Fallow to get a better handle on the weeds, give me time to fertilize, accumulate deep moisture, and make any drainage improvements. That is just me and I am at least half nuts.


Nitrogen carry over from alfalfa is an inexact science. Rule of thumb is a good alfalfa stand will contribute 200 lbs/A/N. Then roughly 25% of any residual is available for each succeeding crop.

If you can find the time, sample the alfalfa for tissue analysis . Clip the top 6 inches off of alfalfa plants. If you are interested in later alfalfa or beans, pay the extra and have them test for Molybdenum also. At the same time probe for a soil sample. You then can compare the two and consider your fertility program for next and following years.

Personally I like to plan my fertilizer program at least one year in advance. Several reasons, but one is soil sampling and analysis is not an exact science. A few years lead gives you time to compensate for some unusual information.
Plant analysis allow you to calibrate your soil test data, plus soil test looses reliability for S, Cu, Fe,Mn, Zn, B, & for sure Mo.
The N, P, K, Mg, & Ca can have 20% or more variability just from the soil's natural variability. I only fully trust the Ph and Organic Matter results. If you are interested in a CEC value pay the money for a measured CEC not a computed CEC.