Step 2 Calculate the maximum limit for N applications to the crop type taking account of any relevant adjustments
Complete Table 1 to calculate the maximum limit for N applications to the crop type.
Enter the crop type, harvest year and N max limit (before adjustments) in the spaces provided above the table (see Leaflet 3 for the N max limits). Then complete columns 1 to 9 for each field growing that crop type.
| Column 1 |
Enter the field name/reference. |
| Column 2 |
Enter the cropped area of the field (ha). |
| Column 3 |
Enter your expected yield. |
Column 4
|
Enter +20 if the soil type is ‘shallow’ and the crop type is autumn or early winter sown wheat or winter barley. |
|
Column 5
|
Enter an appropriate adjustment (see Leaflet 3) to the N max limit if your justifiable expected yield is above the standard yield for the crop type. |
| Column 6 |
Enter +40 if a milling wheat variety is being grown. |
|
Column 7
|
Enter +80 if the current or previous crop has had straw or paper sludge applied to it. |
| Column 8 |
For grassland, enter +40 if three or more cuts of grass are taken from the field. |
|
Column 9
|
Calculate the adjusted N max limit (kgN/ha) for each field. To do this, add the numbers in columns 4 to 8 to the N max limit (before adjustments) that you entered at the top of the table. |
|
Column 10
|
Calculate the maximum limit for nitrogen applications (kgN) for each field (multiply column 2 by column 9). Add up the values in column 10 for all fields and enter this number in box A at the bottom of column 10 to give the maximum limit for nitrogen applications to the crop type. |
Examples of completed versions of Table 1 are provided overleaf.
Note: You can convert the total limit for N applications given in box A into an average and adjusted N max limit for the crop type by:
Dividing the figure in Box A by the total area of the crop type (i.e. the sum of column 2)
This average and adjusted N max limit could prove useful when planning your applications of nitrogen at the start of the growing season to ensure that you do not breach the N max limit.
Examples of Table 1 completed for an arable and grass crop.
Crop type: Wheat, autumn or early winter sown
Harvest year: 2009
N max limit (before adjustments): 220 N kg/ha
Crop type: Grassland
Harvest year: 2009
N max limit (before adjustments): 330 N kg/ha
Table 1. The adjusted N max limits for each field and for the whole area of the crop type.
