ARCHIVE: Fertiliser Manual (RB209)

Other Forage Crops


The amounts of phosphate and potash shown at target Index 2 are needed to replace the offtakes in the fresh yields of each crop as shown in the table, and to maintain the soil at the target Index. The phosphate and potash recommendations at target or lower Indices can be adjusted if yields are likely to be larger or smaller than those shown by multiplying the difference in expected yield by the phosphate and potash content per tonne of yield given in Appendix 5. For example, at P Index 1, the recommendation for forage swedes with an expected yield of 75 t/ha is 75 +(10 x 0.7) = 82 kg P2O5/ha.

Crops grown on soil at Index 0 and 1 would be expected to respond to the extra amounts of phosphate, potash and magnesium shown in the table below. Also over a number of years, these extra amounts of fertiliser will help to raise the Index level of most soils, except light sands.

  SNS Index
  0 1 2 3 4 5 6
  kg/ha
Forage Swedes and Turnips (65 t/ha roots removed)
Nitrogen (N) 100 80 60 40 0-40 0 0
Phosphate (P2O5) 105 75 45 0 0 0 0
Potash (K2O) 215 185 155 (2-)
125 (2+)
80 0 0 0
Forage Rape and Stubble Turnips (grazed)
Nitrogen (N) 100 90 80 60 40 0-40 0
Phosphate (P2O5) 85 55 25 0 0 0 0
Potash (K2O) 110 80 50 (2-)
20 (2+)
0 0 0 0
Fodder Beet and Mangels (65 t/ha roots removed)
Nitrogen (N) 130 120 110 90 60 0-40 0
Phosphate (P2O5) 110 80 50 0 0 0 0
Potash (K2O) 170 140 110 (2-)
80 (2+)
40 0 0 0
Kale (40 t/ha cut)
Nitrogen (N) 130 120 110 90 60 0-40 0
Phosphate (P2O5) 110 80 50 0 0 0 0
Potash (K2O) 260 230 200 (2-)
170 (2+)
130 0 0 0
Forage Rye and Forage Triticale ( 20 t/ha cut)
Nitrogen (N) 80 60 40 20 0 0 0
Phosphate (P2O5) 95 65 35 0 0 0 0
Potash (K2O) 180 150 120 (2-)
90 (2+)
50 0 0 0

Forage rape and stubble turnips

When grown as a catch crop after cereals, apply no more than 75 kg N/ha at Index 0 or 1. Further reductions may be made if the soil is moist and has been cultivated. For stubble turnips sown after mid August, apply 50 kg P2O5/ha at Index 0 only.

Fodder beet and mangels

Salt is recommended on all soils except Fen silts and peats. Apply 400 kg/ha of agricultural salt (200 kg Na2O /ha) well before drilling. If sodium is recommended but not applied, increase potash by 100 kg K2O/ha.

A boron application may be needed. Soil analysis is a useful guide to assess the need for boron.

Phosphate and potash

The recommendations assume that crops are grazed. Where tops are carted off, potash applications may need to be increased by up to 150 kg K2O/ha. Phosphate and potash need only be applied to the seedbed at Index 0 or 1.

Magnesium

Where sugar beet or potatoes do not feature in the rotation, magnesium fertiliser is only justified at soil Index 0 when 50 to 100 kg MgO /ha should be applied every three or four years (see page 42).

Don’t forget to:

make allowance for nutrients applied in organic manures (see Section 2)

ensure the phosphate and potash offtake is balanced by application on Index 2 soils and check that the soil is maintained at Index 2 by soil sampling every 3 – 5 years

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