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Competency Area 5: Seeding Rates and Row Spacing

PO 24. Know the advantages and disadvantages of seeding pure grass or legume stands versus mixed stands.

Pure alfalfa
If the soil is well drained and optimum for alfalfa growth, pure alfalfa is an option. The primary advantage of pure alfalfa seeding is the ability to use weed control, either herbicides or a combination of glyphosate and Roundup Ready alfalfa varieties. Some commercial hay markets may pay a premium for pure alfalfa forage. A pure grass stand can be harvested at the optimum quality for alfalfa. It is possible but problematic to apply manure to pure alfalfa stands. Pure alfalfa will maximize yield and quality on good alfalfa land.

Pure grass
If the soil type is not optimum for legumes, then pure grass can be sown. A perennial grass stand has more options for manure application. A pure grass stand can be harvested at the optimum quality for the grass species, and will increase the spring harvest window.

Mixed alfalfa-grass stands
If conditions are not optimal for alfalfa, a mixture may be planted. Mixed stands eliminate the need to fertilize pure grass with expensive commercial N fertilizer. As alfalfa declines in a mixed stand, grass can fill in the void. Grass will reduce the potential for alfalfa heaving in the spring on fragipan soils prone to heaving. Mixed alfalfa grass can be harvested at a mixture. Over 80% of all alfalfa acreage in NY is seeded to alfalfa-grass.

Mixed grass stands
In some cases where soil types and drainage are highly variable in a given field, it can be advantageous to plant a mixture of perennial grasses. Different locations in the field may end up dominated by different grass species. This can maximize yield but does not optimize quality as grasses of differing quality must be harvested at the same time.