With the late-season harvest these forage stands can provide an opportunity to empty manure pits and provide the crop with needed nutrients for next year. Alfalfa and forage grasses are heavy consumers of soil nutrients.
Book values for nutrient removal by alfalfa are 50 # N, 15 # P2O5 and 50# K2O. Orchardgrass removes 50 # N, 17 # P2O5 and 62 # K2O and Timothy 38 # N, 14 # P2O5 and 62 # K2O per ton of dry matter.
A typical five-ton per acre per year alfalfa crop removes 250 # N, 75 # P2O5 and 250 # K2O and a four-ton orchardgrass harvest removes 200 # N, 68 # P2O5 and 248 # K2O. Without close monitoring with soil test reports or fertilizer budgets, soil fertility levels can be dramatically lowered during the four-year to six-year lifespan.
Fall applications of manure to forage stands can be used to meet the high demands of forage nutrients if some agronomic and environmental considerations are kept in mind. The challenges of manure applications to forages are related to soil and stand conditions.
Fall manure applications are a great time to address P2O5 and K2O levels. They also save time in the spring, when soils also tend to be wetter. Fall manure applications also help root development before winter dormancy and help spring growth get started. Weed scientists report less weed stimulation from fall manure applications compared to spring applications.
Wheel traffic can cause surface and deep compaction when soil conditions are not fit. Over the lifespan of the stand this compaction can lead to reduced water infiltration and decreased surface and deep root development. Injury to the developing shoots and the crowns can also lead to reduced stands.
Drag line manure applications can also injure shoots and crowns. Using flotation tires and smaller loads can reduce these effects but staying off poor soil conditions is important.
Environmentally, fall manure applications can lead to a greater risk of runoff. Applications made to forage stands will limit this risk compared to applications to corn silage fields. Another risk more common in wetter areas is infiltration into tile lines. Producers should be aware of field conditions when applying manure at any time of the year.
Liquid manures are preferable to bedded pack manures on forages. Smothering of the crop and the potential for picking up manure clumps next spring increase with bedded pack manures.
A typical rate of 3,000 gallons per acre of liquid manure in the fall will be adequate. Priority for fall manure applications should be older grass stands first, followed by the oldest alfalfa stands and then younger stands last. Be sure to stay out of waterways and 100 feet away from streams.
Check your crop records and soil test reports to closely monitor soil nutrient levels. It is still possible to take advantage of this fall weather to address nutrient needs and distribute manure to targeted areas. FG
Paul H. Craig
Senior Extension Educator
Penn State University Extension – Dauphin County
phc8@psu.edu
—Penn State Field Crop News, Vol. 11, No. 31
