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Alfalfa-grass and low soil fertility is a poor match

Everett D. Thomas Published on 11 November 2009

After several years of trying with a spectacular lack of success to grow alfalfa-grass on leased land that has very low phosphorus (P) and potassium (K) fertility, I’ve finally had to admit that it’s been a flop.

Oh, the grass grows just fine and we’ve harvested some decent yields from these fields, but grass is so efficient at extracting potassium and other nutrients from the soil that it starves the alfalfa out.

We may get very good establishment of the alfalfa, but as the grass starts to get a foothold (roothold?), the alfalfa almost seems to suck back into the ground. In these situations, grass is a “companion” crop – about like a wolf is a companion to a flock of sheep.

There’s nothing wrong with a good stand of grass, but it’s a really lousy idea to spend the money on alfalfa seed when it will only last a year. Based on our sad experience, we offer these alternatives:

1. Wait until you increase soil test P and K to at least medium levels before seeding alfalfa-grass. This will almost certainly have to be done by relying primarily on liberal (heavy) applications of manure because of the very high price of commercial fertilizer.

2. Seed alfalfa without any grass. The problem with this is that unless the land is uniformly well-drained, the alfalfa will soon die out in the low spots to be replaced by dandelions and weedy grasses. Seed grass at higher rates than you would in an alfalfa-grass mixture.

Many farmers have no idea what an intensively managed, pure grass stand will do because what they’re used to harvesting are run-out alfalfa-grass fields with less than half as many grass plants as needed for optimum yield.  FG

—Excerpts from Miner Institute Farm Report

Everett Thomas
William H. Miner Agricultural Institute