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Chapter 6.1

single crop year. Even if technology allowed, it has been estimated that doing so would likely increase the area required for manure application by anywhere from 3 to 6 times compared to N-based application.

A logical P-based application strategy, if land base allows, would involve applying manure so as to supply three to four years worth of P in a single application. One consideration for using this approach is that while only 70 % of total manure P will be available in the year of application, much of the remaining P will come available over the subsequent two years.

A P-based application strategy that supplies three to four years worth of P will require supplemental N fertilizer applications to support subsequent crops. Annual soil sampling is recommended to determine N fertilization requirements and to monitor levels of soil test P. If soil test P remains high after the third year subsequent manure applications should be delayed. Whenever applying multiple years worth of P take precautions to minimize the risk of P losses in runoff by adopting suitable land management practices (see Chapters 8.2 and 8.3).

If land base relative to manure production is restricted, arrangements will likely need to be made with neighbouring landowners to secure additional area.

Calculate Manure Application Rate

Calculate application rate by dividing the

recommendation for the nutrient being used as the basis for application (i.e., reference nutrient, N or P) by its concentration in the manure.

The generic calculation of manure application rate is:

Application rate =

Reference nutrient recommendation ÷ Reference manure nutrient concentration

Remember that if application is based on P, concentration of available P in the manure must be converted to a P

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basis in order to use the fertilizer recommendations from the soil analysis. In some instances, it may be also be necessary to convert factors in the equation so that the units are consistent.

Case Study: Calculating Manure Application Rate

Recall that manure application will take place under wet, cool conditions, liquid manure will be injected and solid manure is surface applied and incorporated within two days. Application rates will be calculated for the following scenarios: Single-year application based on manure 1.

available N One-time application of two years worth of 2.

manure available N One time, three-year application based on 3.

manure available P

To review:

The liquid manure source contains: •

2.4 g/L crop available N 0.7 g/L crop available P 3.9 g/L crop available K

The solid manure source contains: •

3.3 kg/t crop available N 1.6 kg/t crop available P 6.2 kg/t crop available K

The fertilizer recommendations for the field, •

based on soil test results were 78 kg/ha of N and 39 kg/ha of P

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