Spring is the time for pasture producers to consider interseeding to add to or improve forage in their existing pastures. Interseeding offers an opportunity for improving pasture productivity as well a forage nutritive quality. Interseeding involves using a no-till drill to aid in the incorporation of a legume or a more productive grass into an existing pasture sod. Interseeding is normally done from mid-March through early May, when soil moisture and temperature are suitable for rapid seedling establishment.
Interseeding can be accomplished with relatively few field operations. Opening of the grass sod, shallow seed placement, and seed coverage are required. A number of drills are available that can be used in sod-seeding efforts. Some of these drills may have improved features related to sod penetration, depth control, seed metering, or coverage that improves their effectiveness in sod-seeding situations. Equipment limitations for sod-seeding implements sometimes are overcome by operator experience and home shop modifications.
Legumes interseeded into grass sod should increase pasture yield, improve forage quality, and eliminate or minimize need for nitrogen fertilizer. Clovers, alfalfa, and birdsfoot trefoil have been successfully interseeded. The more efficient seed placement provided by a no-till drill allows many of our more productive perennial forage grasses to also be successfully established by interseeding. Thin, low-producing, grass sod might best be improved by interseeding a grass legume mixture.
When renovating a pasture, select species are suitable for desired use and persistence. When considering forage species to add to an existing site, choose legumes or grasses of similar height, palatability and competitiveness to those already in the pasture. Iowa State University Extension bulletin PM-1792, Selecting Forage Species, covers characteristics of many forage legumes and grasses commonly used in Iowa. A seeding delay into late spring to improve growing conditions also brings a greater competition from the existing grass sod. Close grazing in the fall or early spring, ahead of interseeding, will help to reduce sod competition. Labeled herbicides are sometimes also used to temporarily further reduce competition from plants present in the stand.
Interseeding success depends a great deal on paying attention to details, timeliness, careful management of sod completion, controlling seeding depth to no deeper than ¼ to ½ inch, and a little bit of luck with weather.
Interseeding research has been conducted in many parts of the U.S. and around the world. It shouldn’t come as a surprise that the conclusions from these efforts all point to several very important issues that must be met for successful interseedings. See Iowa State University Extension bulletin PM-1097, Interseeding and No-Till Pasture Renovation for more suggested seeding rates and guidelines.
Source: Steve Barnhart, Extension Forage Specialist, Iowa State University