Seed Potatoes

The recommendations in this section are using the RoI fertiliser classification system and are based on Teagasc research.

Due to slight differences between the RoI and NI classification systems, these recommendations are only a guide for Northern Ireland farmers. They can be converted between the RoI and NI classification systems using this Conversion Table.

Before choosing your fertiliser products please consult your local advisor to ensure that you do not exceed the limits for your farm as determined by the nitrates directive (SI no 31 of 2014)

Table 48. Nutrient Requirements (units/acre)
Index N P K
1 Very Low 124 100 196
2 Low 104 92 148
3 Medium 84 80 96
4 High 64 68 52

Fertiliser Recommendation

Table 49. Application Rate (bags/acre)
Index K1 very low K2 low K3 medium K4 high
P1 very low 12 x7-6-17
1 ¾ x 16% Superphosphate
1 ½ x Sulfa CAN
9 x 7-6-17
2 ¾ x 16% Superphosphate
2 x Sulfa CAN
6 x 7-6-17
4 x 16% Superphosphate
3 x Sulfa CAN
3 x 7-6-17
5 x 16% Superphosphate
4 x Sulfa CAN
P2 low 12 x 7-6-17
1 x 16% Superphosphate
1 ½ x Sulfa CAN
9 x 7-6-17
2 x 16 % Superphosphate
2 x Sulfa CAN
6 x 7-6-17
3 ¾ x 16% Superphosphate
3 x Sulfa CAN
3 x 7-6-17
4 ½ x 16% Superphosphate
4 x Sulfa CAN
P3 medium 12 x 7-6-17
½ x16% Superphosphate
1 ½ x Sulfa CAN
10 x 7-6-17
1 x 16 % Superphosphate
2 x Sulfa CAN
6 x 7-6-17
2 ¾ x 16% Superphosphate
3 x Sulfa CAN
3 ½ x 7-6-17
3 ½ x 16% Superphosphate
3 ½ x Sulfa CAN
P4 high 9 x 7-6-17
1 x Sulphate of Potash
2 x Sulfa CAN
9 x 7-6-17
2 x Sulfa CAN
6 x 7-6-17
2 x 16% Superphosphate
3 x Sulfa CAN
3 x 7-6-17
3 x 16% Superphosphate
3 ½ x Sulfa CAN

*Assuming N index 1
**Potash should be derived from Sulphate of Potash (SOP) rather than Muriate of Potash (MOP)

  • 7:6:17+8% Sulphur (S) containing Sulphate of Potash can give drier potatoes than 10:10:20 containing Potassium Chloride. High Nitrogen (N) rates will increase tuber size, reduce dry matter content and delay maturity.

For all situations, apply C.A.N. or Urea to satisfy the Nitrogen requirements as recommended by your advisor.