Details of hidden rules within the API
There are some hidden rules within the API calculations which can lead to discrepancies between values returned by the API and values in the paper version of RB209.
Default Yields
Some arable crops have a yield adjustment calculation as part of their recommendation.
Therefore in order to calculate a recommendation, a yield is required.
Where a yield is provided, this is used in the calculations.
However, where one is not provided, a default yield will be used in its place.
The crops with default yields are (all in t/ha):
Linseed : 1.5
Spring oilseed rape : 2.0
Spring beans, Winter beans, Winter oilseed rape : 3.5
Peas : 4.0
Spring barley : 5.5
Spring oats, Spring rye, Spring triticale, Spring wheat, Winter oats, Winter rye : 6.0
Winter barley : 6.5
Winter triticale, Winter wheat : 8.0
Potatoes : 50.0
Sugar beet : 60.0
The crops with default yields are (all in t FW/ha):
Wholecrop spring barley, Wholecrop spring oats, Wholecrop spring rye, Wholecrop spring triticale, Wholecrop spring wheat, Wholecrop winter barley, Wholecrop winter oats, Wholecrop winter rye, Wholecrop winter triticale, Wholecrop winter wheat : 30.0
Forage maize : 40.0
Forage swedes (roots lifted) : 65.0
Fodder beet : 85.0
Organic Materials
Where the values in tables in Section 2 of the paper book are specified as 'ND' (No Data), these will be returned as nulls by the API.
While values in the same tables are: 'Trace' or '<0.1', these are set to 0.
Rounding
Recommendation output values are rounded based on certain rules:
Arable values less than 10 are set to 0, values from 10 and above to less than 20 are set to 20, and all values from 20 and above are rounded to the nearest 5.
Grassland values are rounded to the nearest 5.
Lime recommendations are rounded to the nearest 1.
Nutrients applied (applied, total and available) values are always rounded to the nearest 1.
Soil Nitrogen Supply (SNS) Index
When calculating the SNS Index through the Field Assessment Method.
If the field has not been in grass within the past three years, and the soil type is either an Organic soil or Peat soil.
Then the SNS Index will be defaulted to the mid-point Index available during the calculations.
Therefore, for Organic soils, the SNS Index will be defaulted to 4.
While for Peat soils, the SNS Index will be defaulted to 5.
Please note that if you have either Organic or Peat soils, then you are advised to consult a FACTS Qualified Adviser.