CW09-25-09 Forage Soil Tests

CW09-25-09 Forage Soil Tests

September 25, 2009

If you’re planning to plant alfalfa or interseed legumes into pasture next spring, take soil tests and, if necessary, fertilize this fall to help ensure increased production and profits next summer.

Alfalfa and other legumes need more nutrients than most other crops grown here. For example, an average ton of alfalfa hay will contain about 50 lb of nitrogen, 12 lb of phosphate, 50 lb of potash, and 4 lb of sulfur.

Well-nodulated legumes can get their nitrogen from the air, but all other nutrients must come from fertilizer or the soil.

Use soil tests to determine how much nutrition your soil can provide how much more fertilizer, if any, is needed to produce maximum profits.

Collect and analyze samples this fall before soils freeze from fields you expect to plant or interseed next year. Gather one sample from the usual 7- or 8-inch depth plus another one only a couple inches deep. This shallow sample will determine if you have an acid surface layer that many growers have been finding recently. If the pH of your surface layer is below 6 but the deeper sample is above 6.2, you need lime, but only half the usual amount. If possible, apply that lime this fall so it can neutralize that acidity, which will speed seedling establishment next spring.

If tests indicate the field needs phosphorus, sulfur, or potash, these can be applied this fall or you can wait until planting next spring.

Bruce Anderson
Extension Forage Specialist