R.L. Hamblen, Bugwood.org
Overseeding legumes in pastures is a good way to reduce dependence on high-priced nitrogen (N) fertilizer and increase summer productivity and quality.
My preferred seeding method is an electric broadcast seeder mounted on an ATV. You can cover a lot of ground in a day at minimal cost. We generally figure a no-till drill costs about $15/acre for interseeding, while the ATV costs less than $1/acre. The broadcast strategy works well with any clover or birdsfoot trefoil, but not so well with alfalfa. Alfalfa is more susceptible to late-season frost and is better seeded with a no-till drill.
The recommended seeding rate for each species is: red clover--4-6 lbs. /acre; white or alsike clover--1-2 lbs./acre; birdsfoot trefoil--3-4 lbs./acre; and 8-10 lbs/acre alfalfa.
Applying Soil Nutrients
If you took soil samples last fall and need to apply phosphorus (P), potassium (K) or other micronutrients, you can apply fertilizer as soon as the snow melts. Spreading fertilizer with a bit of frost in the ground lets you cross ground that may be impassible a month later when the soil is too wet. However, don't apply fertilizer while the ground is frozen solid 2 inches deep or more, due to the runoff risk. Apply after the main thaw, when a spring cold snap firms the surface again.
What about applying N for spring pasture? I generally don't advise it on a large scale. Most graziers already have too much spring pasture and adding N just aggravates the problem.
In some instances, those 40-60 lbs. of N applied before green-up translates to brush hogging a ton of wasted grass in July. It is better to save the N application for later in the season, when it can help grow grass when you really need it.
If you need to jump-start some pasture for early grazing, consider using 30-40 lbs. of N on a third of your pastures. The extra early grass will let you get cattle off hay a couple weeks earlier.
Choose the pastures most likely to be grazed at the start of the season and fertilize only those. Avoid early N fertilization and grazing on swampy pastures, where early grazing can do a lot of soil damage. With the high cost of N, use it as a specific management tool rather than a blanket treatment.
If you intend to drag pastures, do it as soon as the manure pats are no longer frozen. Drag areas with the heaviest accumulation from winter grazing or hay feeding first.
In mixed grass-legume pastures, the piles contain a lot of legume seeds waiting to germinate. The benefit of dragging early is that more of those seeds will contact the soil, be more likely to germinate and help maintain your legume stand. If you wait until the manure pats are little green hills covered with clover seedlings, you destroy your seed bank. The rule with dragging is: "The earlier the better."