ARCHIVE: Fertiliser Manual (RB209)

Table C.
Soil Nitrogen Supply (SNS) Indices for High rainfall (over 700 mm annual rainfall, or over 250 mm excess winter rainfall) – based on the last crop grown

 

   SNS Index    

 

0

1

2

3

4

5

6

 

SNS (kg N/ha)
SNS = SMN (0-90 cm soil depth) + crop N + estimate of net mineralisable N

  <60 61-80 81-100 101-120 121-160 161-240 Over 240
Light sands or shallow soils over sandstone Cereals,Oilseed rape, Potatoes, Sugar beet, Peas, Beans, Low & medium vegetables, Forage crops (cut), Uncropped land High N vegetablesa

*

* * * *
Medium soils or shallow soils not over sandstone * Cereals, Oilseed rape, Potatoes, Peas, Beans, Sugar beet, Low & medium N
vegetables, Forage crops (cut), Uncropped land
High N
vegetables
* * * *
Deep clayey soils * Cereals, Sugar beet, Oilseed rape, Potatoes, Low & medium N vegetables, Forage crops (cut), Uncropped land Peas, Beans, High N vegetables * * * *
Deep silty soils * Cereals, Sugar beet, Low N vegetables, Forage crops (cut) Medium N vegetables, Oilseed rape,
Potatoes, Peas, Beans, Uncropped land
High N
vegetables
* * *
Organic soils      

All crops - see page 86

|Peat soils        

All crops

a. Index may need to be lowered by 1 where residues incorporated in the autumn and not followed immediately by an autumn-sown crop.

Do not confuse SNS (Soil Nitrogen Supply) and SMN (Soil Mineral Nitrogen).

  • SMN is the measured amount of mineral nitrogen (nitrate-N plus ammonium-N) in the soil profile.
  • SNS = SMN (0-90 cm or maximum rooting depth in shallow soils over rock) + crop N (at time of sampling for SMN) + estimate of available N from mineralisation of organic matter.
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