Planting Perennial Legumes and Grasses
Legumes and grasses have very small seeds that require a well-prepared, fine, and firm seedbed for successful germination and establishment. Rolling or cultipacking the soil before and after planting will result in better establishment. No-till drills can be effectively used to establish legumes and grasses but require special attention to seed-soil contact and compaction problems. Whatever seeding method is used, plant seed 1/4 to 1/2 inch deep.
Date of Seeding
Spring. Spring seedings have more available moisture and produce higher yields in the seeding year. Early planting results in vigorous growth and development before the onset of hot, dry weather. Plant as soon as a good seedbed can be prepared, particularly for perennial grasses. Pure alfalfa seedings can be made as late as the first week of June, but weeds must be controlled with Eptam or Balan. Grass seedings after May 1 in southern New York or May 15 in northern New York have an increased risk of failure.
Late Summer. Late-summer seedings generally have fewer weed problems, can follow another crop, and time and labor management may be easier than in the spring. Success of late- summer seedings depends primarily on adequate rainfall. It is helpful to work the field one or two months before planting, if possible, to conserve moisture for planting. Seedings following another crop, such as winter wheat, are more at risk because the previous crop removes most available moisture. Alfalfa should be seeded in early August in northern New York to mid-August in southern New York. Birdsfoot trefoil and reed canarygrass should be seeded in late July because both need at least six weeks of fall growth before a hard freeze. Perennial grasses other than reed canarygrass should be seeded by mid-August in northern New York or late August in southern New York.
All legume seed should be well mixed with the proper fresh rhizobium inoculum shortly before planting. Preinoculated seed may not require treatment. The small cost and time required for treating all seed with inoculant at planting, however, is good insurance for effective nitrogen fixation by the legume.
Fertilizers and Lime for Legume Establishment
Use soil tests to determine the lime and fertilizer requirements of each field. Plan the time of seeding well ahead so lime can be applied the year before seeding. This is particularly important when pH is low (acidic soil) and 3 or more tons of lime per acre must be applied. See “Forage Fertilization” for lime and fertilizer guidelines.
Phosphorus is very important when planting legumes. Adequate amounts are needed for rapid vigorous growth of legume and grass seedlings. Phosphorus applied at the time of seeding will increase the size and vigor of plants even on soils that have a medium to high soil test level of phosphorus.
Nitrogen is not required for the establishment of legumes or legume-grass mixtures. Applying nitrogen to legume seedings may deter nitrogen fixation by the legume and will increase competitive growth of grasses and weeds. See the Cornell Field Crops and Soils Handbook for a detailed discussion of fertilization of forage crops.
Companion crops (also known as nurse crops) established in the spring with alfalfa, alfalfa-grass, or perennial grass seedings should provide weed control and a high-quality supplemental forage. If they put the perennial forage at risk, however, companion crops become a detriment to farm profitability. Growing small grains for a grain crop while attempting to establish a perennial forage is not worth the risk. Lodging of small grains or small-grain/field pea combinations will likely damage a new seeding.
Alfalfa can be successfully established using small grains and small-grain/field pea combinations as companion crops. Small grains are moderately successful for weed control if planted before May 1 but generally unsuccessful after May 1. Small-grain companion crops should be harvested before heading to provide adequate forage quality. Small grains harvested at a later maturity stage will provide an adequate heifer or beef forage.
Companion crops are not currently recommended with alfalfa-perennial grass mixtures because of concern over the weak grass seedlings. In particular, spring companion crops can be very competitive with establishing reed canarygrass.
A perennial legume and grass species selection tool for New York State that is site-specific and use-specific can be found at www.forages.org.