The goal of decreasing silage effluent is one more good reason to put up your silage at near-optimum moisture content.
Effluent is corrosive and is actually a potent pollutant. An Irish government publication says silage effluent has a biochemical oxygen demand (BOD) of up to 200 times that of raw sewage. It says 500 tons of unwilted silage has the same polluting potential as the daily untreated sewage from a city of approximately 200,000 people.
Penn State University says as little as one gallon of silage effluent can lower the oxygen content of 10,000 gallons of fresh water to a level dangerous to fish survival, and that nutrient concentration of silage effluent, in terms of N, P and K, is very similar to typical liquid dairy manure.
Penn State Ag Engineer John Tyson adds that the pH of effluent is about 4.0 and usually varies from 3.5 to 5.0, which is in the range of vinegar to tomatoes. Battery acid is usually pH of about 1, but the pH of silage effluent is corrosive to steel and damaging to concrete.
Although some effluent is unavoidable, large amounts cost you nutrients and value because it indicates high moisture content in the silage, along with associated problems. Also, effluent contains water soluble carbohydrates, protein and minerals, which it is carrying away from your expensive feedstuff.
The Australian online manual of silage management says effluent flow from silage nearly stops as dry matter content reaches 30 percent, and increases as dry matter decreases. See the accompanying chart on silage effluent production according to dry matter content.
Although the volume of effluent produced depends on the moisture content of the crop being ensiled, several sub-factors can alter those guidelines. These include maturity of the crop, degree of wilting, weather conditions, the use of additives and absorbents, and whether the silo is roofed or unroofed.
A publication from the Scottish government says the peak flow of effluent normally occurs within 2 to 3 days of ensiling the crop. Up to 50% of the total volume of effluent is produced in the first 10 days.
Beyond harvesting and wilting for the 30-percent dry matter target, the next management steps are containment. A 2014 article in the Journal of Environmental Management says the second step is to ensure the integrity of silos and effluent storage facilities, and next to establish infrastructure for effluent disposal.
Silos should be located away from waterways and wells. Prepare the site to collect effluent and ideally to store it for your method of disposal. Also, work to divert rain water and runoff away from the silage and the effluent.
Engineers from the NRCS, universities and conservation districts can help with silage storage planning.
Penn State's Tyson says one of the most common method for handing silage effluent is incorporating it into a liquid manure system. He warns you should be careful when mixing silage effluents with manure because hydrogen sulfide and other poisonous gases are produced. Do not mix under a covered facility where those gases can't escape, he adds.
Another favored option is land application to a crop field or grass filter strip, Tyson says. Because of the nutrient density and acidity, effluent must first be diluted with water if applied to a growing crop, he says. Typically a 1-to-1 ratio is adequate. The effluent can be directly applied to fields with a non-growing crop.