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Calculating Manure Application Rates and Fertilizer Requirements

For the solid manure source in the above example, total P would be applied in excess of crop requirements. This means that if this manure was applied annually, based on a single year’s requirement of available N, P would begin to accumulate in the soil.

This example illustrates the value of doing these calculations as well as the value of soil and manure testing. Depending on the natural risks (e.g., presence of neighbouring water bodies, high soil test phosphorus) associated with this field it might be advisable to consider basing application on P recommendations. Remember that if you choose a P-based application strategy soil N and P status needs to be monitored to ensure adequate nutrients for subsequent crops.

Manure Supply versus Available Land Base

If a farm-scale, multiple field nutrient management plan is being developed it is important to determine whether the supply of manure will exceed the available land base eligible to receive manure.

Calculating the land base required to apply stockpiled manure requires three pieces of information:

manure application rate • area eligible to receive manure • total volume or weight of manure to be applied •

The method for calculating manure application rates was described earlier in this chapter. The area eligible to receive manure is determined during the site assessment, taking into account physical limitations and legislated application setbacks.

Refer to Chapters 3.1 and 3.2 for more information on site assessment and determining the area of a field eligible to receive manure. Legislated constraints to manure

application under the Agricultural Operation Practices Act (AOPA), which also impacts area available for application can be found in Chapter 4.4.

Use either standard estimates for manure production or estimate volume directly using the procedures and calculations outlined in Chapter 4.1 (preferred method). Solid manure is expressed in terms of weight, which requires that density of the material be considered. In the absence of a measured density average values for common livestock manures are presented in Table 6.1.2.

Table 6.1.2 Estimated Density of Selected Solid Manure Sources

Species/Class

Manure Density kg/m 3 lb/ft 3

Beef, cows/finishers 655 40.9 Beef, feeders 641 40.0 Swine, farrow-to-finish 796 49.7 Swine, grow/finish 772 48.2 Poultry, broilers/pullets 320 20.0 Poultry, turkey toms 248 15.5 Sheep, ewes/rams 497 31.0 Goats, general 497 31.0 Horses, feeders 529 33.0

Derived from values presented in AOPA: Manure Characteristics and Land Base Code (2006).

In the event that manure supply exceeds eligible land base, additional land will need to be found in order to apply manure sustainably. This may require arrangements or formal agreements to be made with neighbouring landowners.