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The Potash Development Association

Potash for Cereals

Nutrient removal and balance

Phosphate

Typical removal in cereal grain is 7.8 kg P2O5/t. Phosphate content of straw is very much lower than potash. Removal of straw thus has little effect upon phosphate offtake.

Typical removal standards

    Metric
kg/t of grain
Imperial
units/t of grain
    P2O5 K2O P2O5 K2O
Cereals - Grain only 7.8 5.6 15.6 11.2
  - Grain & Straw
Winter wheat/barley
8.4 10.4 16.8 11.2
  Spring wheat/barley 8.6 11.8 17.2 23.6
  Oats 8.8 17.3 17.6 34.6

Recommendations

The recommendations below are calculated to achieve full yield and maintain, improve or reduce soil P and K according to the soil Index. The approach firstly identifies the amount of nutrient removed by the cereal crop grown (the 'maintenance' amount) and then makes additions to this if necessary (soil fertility adjustment), according to the current soil Index level.

Phosphate

Maintenance requirement
(replacement of P removed)
Metric
kg/P2O5/ha
Imperial
units/P2O5/acre
Grain only - All cereals yield t/ha x 7.8 yield t/acre x 15.6
Grain + Straw    
  Winter wheat/barley yield t/ha x 8.4 yield t/acre x 16.8
  Spring wheat/barley yield t/ha x 8.6 yield t/acre x 17.2
  Oats yield t/ha x 8.8 yield t/acre x 17.6

 

Soil fertility adjustment - additional phosphate requirement at soil Index 0 or 1
  Metric Imperial
P Index 0 1 2 0 1 2
mg/l 0-9 10-15 16-25 0-9 10-15 16-25
  kg/P2O5/ha units/P2O5/acre
Phosphate requirement +60 +30 0 +50 +25 0

Potash

Maintenance requirement
(replacement of K removed)
Metric
kg/K2O/ha
Imperial
units/K2O/acre
Grain only - All cereals yield t/ha x 5.6 yield t/acre x 11.2
Grain + Straw    
  Winter wheat/barley yield t/ha x 10.4 yield t/acre x 20.8
  Spring wheat/barley yield t/ha x 11.8 yield t/acre x 23.6
  Oats yield t/ha x 17.3 yield t/acre x 34.6

 

Soil fertility adjustment - additional potash requirement at soil Index 0 or 1
  Metric Imperial
K Index 0 1 2- 0 1 2-
mg/litre 0-60 61-120 121-180 0-60 61-120 121-180
  kg/K2O/ha units/K2O/acre
Adjustment +60 +30 0 +50 +25 0
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