Submitted to: Hoard's Dairyman
Publication Type: Trade Journal
Publication Acceptance Date: July 1, 2000
Publication Date: N/A
Technical Abstract: With expanding dairy herds, farmers must deal with larger amounts of manure. Many farmers avoid spreading manure on alfalfa, but alfalfa is very effective at removing excess nutrients. Farmers also can reduce the per acre nutrient loading rates on the farm by expanding manured acreage. But manure application can cause problems, such as 'scald'. Low oxygen availability is the culprit here. Scald may be induced by the combination of high soil water content, blocked soil pores, and high biological oxygen demand (BOD) that follows manure pond water application. Delaying irrigation with dairy manure pond water until alfalfa has recovered from harvest may help, as should reducing the content of solids and BOD. Another problem with manure is its salt content. Most commercial alfalfa varieties are moderately sensitive to salinity. Good irrigation and manure management are needed to avoid salt accumulation. Many weed seeds remain viable after passing through the ruminant digestive tract; some even germinate better afterward. But dormancy, hard seededness, and germination of many plant seeds are improved by high concentrations of nitrate and carbon dioxide in the soil, both of which increase after manure application. Finally, more alfalfa hays contain too much potassium (K), which can make ration balancing difficult. Farmers should use standard soil tests to diagnose K supply and forage tests to tell whether the ratio of K to calcium and magnesium is unfavorable. With all crops, managing irrigation of fresh water is important, but it's far more so for manure pond water, because of possible nutrient and bacteria runoff in tailwater and leaching into ground water.