ARCHIVE: Fertiliser Manual (RB209)

Table A.
Soil Nitrogen Supply (SNS) Indices for Low rainfall (500-600 mm annual rainfall, up to 150 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, Low N vegetables, Forage crops (cut) Sugar beet, Oilseed rape, Potatoes, Peas, Beans, Medium N vegetables,
Uncropped land
High N vegetables * * * *
Medium soils or shallow soils not over sandstone * Cereals, Sugar beet, Low N vegetables, Forage crops (cut) Oilseed rape, Potatoes, Peas, Beans, Uncropped land Medium N vegetables High N vegetablesa * *
Deep clayey soils * * Cereals, Sugar beet, Low N vegetables, Forage crops (cut) Oilseed rape,
Potatoes, Peas, Beans,
Medium N
vegetablesa, Uncropped
land
High N vegetablesa * *
Deep silty soils * * Cereals, Sugar beet, Low N vegetables, Forage crops (cut) Oilseed rape,
Potatoes, Peas, Beans,
Medium N
vegetablesa, Uncropped
land
High N vegetablesa * *
Organic soils      

All crops - see page 86

|Peat soils        

All crops

a. Index may need to be increased by up to 1 where significantly larger amounts of leafy residues are incorporated (see Step 5). Where there is uncertainty, soil sampling for SMN may be appropriate.

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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