Page 234 - Nutrient Management Planning Guide

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Calculating Manure Application Rates and Fertilizer Requirements

When calculating manure application rates •

consider the available nutrient content of manure, soil test results, crop nutrient recommendations and the application strategy (application method and basis for rate calculations). Once the basis for calculating application •

rates has been determined the application rates for N and P can be calculated by multiplying their estimated content in the manure by the application rate. If applying multiple years worth of manure, be sure to factor in mineralization of manure nutrients. There can be substantial excess application •

of certain nutrients depending on whether application rate is P-based or N-based. After calculating a target application rate, calculate the rates at which other nutrients will be applied. Portions of residual organic N and P applied will become available in subsequent years.

Dividing the annual volume or weight of •

manure to be applied by the available land base will give the threshold application rate for an operation. By comparing this to the calculated application rate it is possible to determine whether the available land base will be sufficient. Estimating fertilizer requirements is easier •

because fertilizer recommendations are expressed on the same basis as fertilizer nutrient content, fertilizer nutrients are in crop-available forms and fertilizers can be custom blended to achieve a particular nutrient ratio.

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