There are two calculators in this app, the Quick Calculator which is for travelling irrigators, and an Advanced Calculator which is for slurry tankers and muck spreaders.
The Quick Calculator allows you to choose the type of effluent you are spreading (each type has different standardised nutrient values, solids content) or if you have had your effluent tested, it allows you to enter those values. It gives the option to calculate spreading based on either N loading or application depth.
The Advanced Calculator performs similar functions to the Quick Calculator but has more input fields to account for the additional variables for slurry tankers and muck spreaders. As well as nutrient loading, this calculator also determines the area required for spreading and the number of loads that are required.