Manure on Forages

Knowledge Nuggets

• Manure contains valuable nutrients, such as nitrogen, phosphorus, potassium and sulphur and essential micronutrients, such as calcium, magnesium, copper, manganese, iron and zinc.

• Manure improves some of the physical properties of soil, including water inflitration, aggregate size and stability, pore size and crust strength. These improvements translate into better soil quality.

• Test soils and manure annually, and keep records of manure analyses and application rates on each field.

• Apply manure to meet crop nutrient requirements. Phosphorus-based rates are better because excess P will accumulate in soil if manure is applied based on N requirements of crops. Alternatively, apply at an N-based rate but then do not re-apply until soil tests indicate that available P levels are low enough to warrant another application.

• Perennial forage land provides options for manure application throughout the growing season, rather than just at the beginning or end of the season as with cultivated crops. Manure may be spread immediately after a hay harvest or on pasture after livestock have moved to a new paddock.

• Perennial forages can use more nutrients than annual crops becasue they grow for a longer portion of the year. As well, the extensive root system of forages, and the deep root system of alfalfa in particular, can scavenge nutrients from the soil profile more efficiently than annual crops. The relatively high water use of perennial crops also decreases deep percolation of water and the probability of groundwater contamination.

• Inject liquid manure to conserve N and reduce odour impacts. Keep the deflector angle low to reduce airflow through the manure in order to reduce odour emissions.

• Avoid applying manure when moisture conditons could lead to soil compaction.

• If fall application is necessary, delay application until the soil temperature is less than 10 C. This will reduce mineralization and potential leaching losses.

• Choose fields that are a low risk for runoff (e.g. low slope, good plant cover) or that do not have a nearby common body of water.

• Delay re-introduction of livestock into manured fields to allow forage regrowth and pathogen death in order to reduce the potential for disease transference in the herd.