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### **Introduction**

Dairy manure can be successfully applied to alfalfa both prior to
planting and after estab­lishment. Manure provides a source of major
nutrients and micronutrients. Added benefits may result from improved
soil physical proper­ties and increased biological activity. However,
inappro­priate application may burn leaves reducing yield and forage
quality. Heavy application equipment may compact soil and damage alfalfa
crowns thereby lowering yield and shortening stand life. In weakened
alfalfa stands, nitrogen (N) in manure may stimulate the growth of
grasses and weeds, further diminishing the pro­portion of alfalfa in the
sward.

Other crops such as corn and grass hay should be the preferred crops for
manure application by dairy farmers. Cornfields closest to the barn
often receive manure at rates above crop requirements, resulting in N
imbalances and over application of P and K. Alfalfa and other forage
legumes will use applied N from manure. These crops do not require
supplemental N due to their ability to fix atmospheric N. Manure
applications to alfalfa may be necessary on dairy farms with herds that
produce more manure than can be used on available cropland. Manure
application to alfalfa would increase the total land area available for
spreading, and thus would decrease the amount spread on any one field,
improving the N balance, lessening the potential for nitrate leaching.
Research shows manure application to alfalfa could decrease symbiotic
N~2~ fixation.

### **Recommendations**

### *Pre-plant Manure Applications*

-   Use information from manure analysis of N, P, and K concentrations
    to set rates adequate to supply needed nutrients according to soil
    test recommendations.

-   Avoid applying manure at nutrient rates greater than the alfalfa
    crop can use and en­sure adequate incorporation so alfalfa seed is
    not planted in areas of excessive manure concentration. These may
    result in poor alfalfa stands and increased weed growth. Apply
    manure P and K only to balance the crop need for the entire crop
    rotation.

-   Spread manure when soils are firm so wheel traffic by the manure
    spreader will not cause excessive soil compaction and future stand
    problems.

### *Manure Applications to Established Alfalfa Stand*

-   Apply manure to the forage fields contain­ing the highest proportions
    of grass since these fields will benefit most from the manure N.
    Usually these fields will be the oldest stands, although application
    to estab­lished pure young alfalfa stands is possible without
    detriment where N utilization is the objective. Watch soil test
    levels of P and K.

-   Liquid or solid dairy manure can be applied. Excessive rates may
    contribute to salinity problems and cause salt burn (or scald with
    dairy pond water) to the alfalfa leaves or suffocate plants. An
    increase in nitrate leaching can be expected if plant nutrients
    exceed crop requirements.

-   Manure should be applied immediately (within one or two days) after
    removing a cutting. This reduces the risk of salt burn and forage
    palatability problems.

-   Spread manure only when soils are firm, to reduce soil compaction,
    prevent field rut­ting, and minimize damage to the plant crowns.

-   The most efficient use of the nutrients in manure would occur when
    manure is ap­plied to the alfalfa at the P utilization rate, or to
    the rate that would maintain the soil test level P for the entire
    crop rotation (corn, small grain and alfalfa).

-   Solid manure spreaders should be adjusted to break up large manure
    clumps that might smother regrowth.

###  *Weeds*

-   One of the major farmer concerns for appli­cation of manure on
    alfalfa is weed intru­sion. Presence of weed seeds in manure varies
    and depends on type of farm opera­tion, feeds, and manure management.

-   Research shows proper application of manure at the optimum rate does
    not in­crease weed problems and does not signifi­cantly alter stand
    purity.

### *Residual effects* 

-   Application of manure to alfalfa will benefit succeeding crops both
    from residual N and other essential plant nutrients like P and K.

-   Research shows corn planted after manured alfalfa in the rotation
    may not need any extra N and P fertilizers. Additional N fer­tilizer
    application should be based on pre­plant or the pre-sidedress soil N
    test in applicable regions. Application of N fer­tilizer to corn
    following manured alfalfa may result in overfertilization and
    thereby increase nitrate leaching potential.

-   Application of manure to alfalfa at the N requirement rate will
    over-supply P and K to the subsequent crops and build up soil test
    levels of these nutrients to environ­mentally hazardous levels.

### **Bibliography**

Daliparthy, J., S. J. Herbert, L. J. Moffitt, and P. L. M. Venman. 1995.
Herbage production, weed occurrence, and economic risk from dairy manure
application to alfalfa. J. Prod. Agric. 8:495-501.

Daliparthy, J., S. J. Herbert, and P. L. M. Vene­man. 1995. Excess dairy
manure management: Impact on groundwater quality. pp 343-354. *In* K.
Steele (ed.), Animal Manures and the Land-Water Interface Conference.
Lewis Publishers. Boca Raton, Florida.

Daliparthy, J., S. J. Herbert, and P. L. M. Vene­man. 1994. Dairy manure
applications to alfalfa: crop response, soil nitrate, and nitrates in
soil water. Agron. J. 86(6):927-933.

Herbert, S.J., J. Daliparthy and P.L.M. Veneman. 1993. Application of
dairy manure on alfalfa. Proceedings XVII Int. Grassland Congress:
830-831.

Peterson, T. A., and M. P. Russelle. 1991. Alfalfa and the nitrogen
cycle in the corn belt. J. Soil Water Conserv. 46:229-235.

Schmitt, M. A., C. C. Sheaffer, and G. W. Ran­dall. 1991. Utilization of
liquid manure in alfalfa production. p. 30-37. In Proc. 21^st^ Natl.
Alfalfa Symp. Rochester, MN. 14-16 Feb. Certified Alfalfa Seed Council,
Davis, CA.

Schmitt, M. A., C. C. Sheaffer, and G. W. Ran­dall. 1993. Preplant manure
and commercial P and K fertilizer effects on alfalfa production. J.
Prod. Agric. 6:385-390.