Nutrients in stored feed are not only a good source of cattle nutrition, but also an excellent source of crop fertilizer. Research by the University of Saskatchewan has shown that in-field feeding promotes better recycling of feed nutrients from manure than do corral feeding systems.
“Stored feeds such as alfalfa hay, grass hay or cereal silage contain significant concentrations of nutrients such as nitrogen, phosphorus and potassium,” says Gordon Hutton, development officer, Alberta Agriculture and Rural Development, Airdrie. “Cattle retain only a small portion of the nutrients found in stored feeds. The vast majority of the feed nutrients are excreted in the urine or the dung. Feed nutrients also accumulate on winter feeding sites through feed waste.”
In more traditional corral feeding systems nutrients accumulate in the bedding pack. With in-field feeding, excreted nutrients and feed waste accumulate in the field.
“Nitrogen especially benefits from in-field feeding,” says Hutton. “A winter feeding project at the University of Saskatchewan resulted in 30 to 40 per cent of the feed nitrogen being recovered after in-field feeding on a grass pasture versus only one per cent after corral manure was applied to the pasture. The higher nitrogen capture with in-field feeding is due in part to the reduction in nitrogen losses from off-gassing that occurs within corral feeding systems.”
Bale grazing, bale processing or portable bunk feeders are examples of commonly used in-field feeding systems. The distribution of nutrients from urine, dung or feed waste in the field will vary with the size of the feeding area, quantity of feed delivered, length of feeding period and feed type. Legume-based feeds generally provide the highest nutrient concentrations.
Winter feeding on old grass pastures may be one of the most promising options. Most older pastures are low in soil fertility and, as result, low in forage productivity. With winter feeding, high amounts of plant available nutrients can be introduced to the pasture and recycled through new forage growth over the next few growing seasons.
“However, there are limitations to in-field feeding,” says Hutton. “One of the challenges is managing nutrient placement. Regular rotation of feeding sites, bedding areas and water sources will improve urine, dung and feed waste distribution.”
“As we enter this years winter feeding period it may be worth while to reassess how we handle the nutrients in stored feed supplies,” adds Hutton. “With the rising costs of commercial fertilizers, stored feed nutrients may have an increasing value for use as not only a livestock nutrient but also as source of crop fertility.”