Main Crop 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 46. Nutrient Requirements (units/acre)
Index N P K
1 Very Low 136 100 244
2 Low 116 80 196
3 Medium 96 60 148
4 High 68 40 96

Fertiliser Recommendation

Table 47. Application Rate (bags/acre)
Index K1 K2 K3 K4
P1 12 x (7-6-17+s)
+
2 x (10-10-20)
+
1 x (CAN
10 x (7-6-17+s)
+
2 x (16%P)
+
1 X (7-6-27)
+
2 X (CAN)
10 X 7-6-17+S)
+
2 X (16%P)
+
2.5 X (CAN)
7 X (7-6-17+S)
+
3 X (16%P)
+
3.25 X (CAN)
P2 9 X (7-6-27)
+
1.25 X (16%P)
+
2.75 X (CAN)
9 X (9-8-18.5)
+
1.5 X (7-6-17+S)
+
1.75 X (CAN)
10 X (7-6-17+S)
+
1.25 X (16%P)
+
2.5 X (CAN)
5 X (10-10-20)
+
2 X (16%P)
+
3 X (CAN)
P3 9 X (7-6-27)
+
2.75 X (CAN)
9 X (7-6-24)
+
2.75 X (CAN)
7 X (9-9-21)
+
2.75 X (CAN)
6 X (9-8-18.5)
+
0.75 X (16%P)
+
3 X (CAN)
P4 6.5 X (7-6-27)
+
1.5 X (SULPHATE OF POTASH)
+
3.5 X (CAN)
6.5 X (7-6-27)
+
0.5 X (SULPHATE OF POTASH)
+
3.5 X (CAN)
6.5 X (7-6-24)
+
3.5 X (CAN)
5 X (9-8-18.5)
+
3.5 X (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.