Applying Target Rates of Lagoon Water Nitrogen
A nitrogen budget usually calls for a specific amount of nitrogen to be applied to the field. When using liquid manure (lagoon water), this is done by mixing the appropriate amount of lagoon water into the fresh irrigation water. The amount to mix in depends on how long the irrigation will run and the concentration of nitrogen in the lagoon water.
By far the easiest way to apply a specific rate of lagoon nutrients is to use a flow meter and control valve.
If you are using pump output or gravity flow gpm method of measuring flow, applying a target rate of nutrients is awkward and imprecise but it can be done. Here's how:
In most cases, there really isn't a good way to use pond drop to proactively apply a specific target application rate. You can, however, estimate the flow rate out of the pond at different pond depths and use the gpm method for targeting applications.
This publication has instructions for estimating gpm from a pond, as well as ideas for other measurement methods:
Tools to help you determine the flow rate (gpm) from a lagoon pump or a gravity flow pond outlet are here:
Visit the recordkeeping page to find worksheets and spreadsheets that will help you keep track of what you've applied.