Guide Index System

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.

The Goulding Fertilisers recommendations are based on the Index System as laid out by Teagasc, Johnstown Castle, Co. Wexford. In the recommendations, the soil fertility is divided into 4 indices:

Table 1. Fertiliser Index System
1 = Very Low 2 = Low 3 = Medium 4 = High

The Index for Phosphorus (P) and Potassium (K) can be established by a soil test, whereas the Nitrogen (N) Index is based on a knowledge of:

  • soil type
  • area knowledge
  • previous cropping

(a) Phosphourus (P) and Potassium (K) Index System

The Index and the corresponding soil test range for P and K are shown in Table 2 Below:

Index Soil P ranges (mg/l) Soil K ranges (mg/l)
Grassland Other Crops Grassland and Other Crops
1 0 – 3.0 0 – 3.0 0 – 50
2 3.1 – 5.0 3.1 – 6.0 51 – 100
3 5.1 – 8.0 6.1 – 10.0 101 – 150
4 > 8.1 > 10.1 > 150
Table 3. Phosphorus (P) and Potassium (K) response at the Index range
Index Response Level
1 Very Low Nutrient response definite
2 Low Nutrient response likely
3 Medium Nutrient response unlikely, except for root crops, but maintenance dressing should be used
4 High Nutrient levels adequate, Maintenance dressings not necessary at presence except for potatoes

(b) Nitrogen (N) Index System

The Nitrogen Recommendations are based on the requirements of each particular crop, taking into account:

  • the previous cropping
  • the manuring history of the field
  • the soil type
Index Response Level
1 Very Low Small release of soil Nitrogen (N) (continous tillage)
2 Low Medium release of soil Nitrogen (N)
3 Medium Large release of soil Nitrogen (N)
4 High Very large release of soil Nitrogen (N)

Tillage / Pasture Establishment:

Continuous tillage: — crops that follow short leys (1-4 years) or tillage crops
Previous crop
Index 1 Index 2 Index 3 Index 4
Cereals, Maize Sugar beet, Fodder beet, Potatoes, Mangels, Kale, Oil seed rape, Peas, Beans
Leys (1-4 years) grazed or cut and grazed.
Swedes removed Swedes grazed in sitiu
Vegetables receiving less than 200 kg/ha nitrogen Vegetables receiving more than 200 kg/hanitrogen
Tillage crops following permanent pasture
Nitrogen Index
Index 1 Index 2 Index 3 Index 4
The 5th tillage crop following permanent pasture. For subsequent tillage crops use the continuous tillage table The 3rd or 4th tillage crop following permanent pasture. If original permanent was cut only use index 1 The 1st or 2nd tillage crop following permanent pasture (see also Index 4). If original permanent pasture was cut only, use index 2 The 1st or 2nd tillage crop following very good permanent pasture which was grazed only

Grassland

The Nitrogen Index is not very useful for grassland as it depends on:

  • the stocking rate
  • age of the ley
  • variety of grasses in the sward
  • clover content

Under a grazing situation, newly re-seeded leys generally need more Nitrogen in the first three years of production than in succeeding years.

(c) Sulphur

Some thirty percent of our soils require Sulphur for optimum yields because:

  1. Fertilisers containing high sulphur contents are used little nowadays.
  2. Sulphur deposition on land has declined because of lower emissions from industry. The soils most likely to show Sulphur deficiencies are sandy, free draining soils with a low organic matter content. As the sulphate ion leaches readily from soils, it is not worthwhile trying to build-up soil sulphur levels.
Table 7. Teagasc recommended application rates of Sulphur
Grazing 10-20 units/acre/yr
Silage 15-20 units/acre/cut
Cereals 15-20 units/acre/yr
Roots 15-20 units/acre/yr

Gouldings produce a large range of core products with or without Sulphur. For information on these products view our product range.