Jerry Cherney – E.V. Baker Professor of Agriculture, Soil and Crop Sciences Section
Alfalfa growth is generally stunted this spring, while grass is moving along, probably heading about normally, but probably shorter than normal.
We sampled alfalfa-fescue at the end of last week and tested our app. Alfalfa was 12” max height and had a rosette-type growth. Our alfalfa-grass computer/phone app (http://220.127.116.11:8080/) over predicted grass% in the mixture by about 10% units, likely due to the compact alfalfa growth. The correlation between our predicted grass% and the actual separated DM grass % was very good at 0.95, but was biased upward on the app due to the alfalfa stunting. 12” alfalfa is marginal height for any equation estimations of either percent or NDF.
As far as spring harvest, it depends on the grass% in the mixture:
More than 50% grass in the stand: Harvest like a grass stand and ignore the alfalfa. Orchardgrass is in boot stage now in many locations.
Less than 25% grass in the stand: Wait for a little more alfalfa growth (more like a PEAQ chart), to minimize chances of damaging alfalfa stand. Grass will be more mature than normal.
25-50% grass: Something in between. Harvest a little earlier than normal for alfalfa.
Not clear if the alfalfa is going to bolt once temperatures rise or just start growing at a normal pace.
Most likely alfalfa height will not have a normal relationship with NDF as it typically does. Keep in mind that the alfalfa has continued to mature (increase in fiber, lignify) even if it is not growing upward much.