Grassland Nitrogen Fertiliser Recommendations

Take Home Messages for good hi input medium & long term swards on schillet and granite based soils below 1000ft

Grazing N 270 units total starting Valentines day - first 3 applications can be Urea
On extreme slopes with less than 15" soil it is doubtful more than 200N is required
Silage 1st cut where slurry normally applied 110-120N, if Nil Slurry 130N as Urea all applied 1st 2 weeks March
If cutting hi sugar varieties before Mid May apply Last week Feb, 1st week March Latest
Liquid nitrogen should never be injected in grassland situations.

Cornwall adaptation to MAFF Booklet RB2009

Most of Cornwall is below 1000ft, has an  April - September  rainfall at or above 16" and is favoured with medium depth easily workable relatively free draining loams.  There is a long growing season - typically 4-6 weeks longer most areas of the UK.  For most situations other than cliff tops, extreme slopes, Moor or Culm measures poorly drained, altitude or dune sand, Cornwall can be described as having Good Growth Potential.  As others have described it - this is Boy's ground - or at least 8 out of 10 years it is!  The North Atlantic Oscillation (the Atlantic's version of the Pacific's El Nino / El Nina) gave England's most westerly gale blown county it's wettest Autumn for 200 years in the millennium year

1. Grazing

 

Grazing N fertiliser for Cornwall below 1000ft: Good Growth Potential  UNITS PER ACRE

Soil Nitrogen status will be High if this is a permanent sward grazed at over 200 N in previous years or is normally cut once - twice early but typical lagoon slurry is applied for the 1st cut at 3000gal per ac.

SNS status 50Kg Bags per acre SNS 50Kg Bags per acre SNS 50Kg Bags per acre
Month Low N 34.5% Urea 46% Mod N 34.5% Urea 46% High N 34.5% Urea 46%
Valentines day 55 1.6 1.2 55 1.6 1.2 55 1.6 1.2
Late Mar-E. April 65 1.9 1.4 55 1.6 1.2 55 1.6 1.2
Late Apr-E. May 65 1.9 1.4 55 1.6 1.2 45 1.3 1.0
June 55 1.6 55 1.6 45 1.3
July 55 1.6 55 1.6 35 1.0
August 45 1.3 35 1.0 35 1.0
Units/bags/ac 340 9.9 4.0 310 9.0 3.6 270 7.8 3.4
Notes
Ave or V.Good grass growth site deduct or add 30 Units N per acre to the total N application.
Above 300 M - 1000ft deduct 30 Units per acre and delay Mid Feb nitrogen too  late Feb - early March
In dry summers If no or little grass growth following the month of application omit the next scheduled application On extreme slopes if there is normally little grass growth mid summer do not apply July / August Nitrogen
Urea (46% N) Nitrogen applied, as urea is rapidly available for uptake. Plants do not absorb urea-N, it is rapidly hydrolysed to ammonium and nitrate-N within a few days. For this reason, in cool wet conditions (late winter) it is less disposed to leaching losses. On calcareous (chalk - limestone) or excessively limed (pH over 7.5) soils or under dry soil conditions, urea looses ammonia gas to the air. It should only be used in these circumstances with caution. That said Urea is usually equivalent to ammonium nitrate when applied in Feb - April and is therefore suitable for 3 grazing applications, 1st cut and winter cereal N. Do not use when soils are dry and warm (any time late May June July August) - however if doing so - apply immediately before rain.
For sodium fertilisers please check Testing Grass page

 

2. Silage

 

Grass Silage Nitrogen: Good Growth Class below 1000ft (300m) UNITS PER ACRE

Soil N Status will be Moderate if this is a permanent sward that normally receives slurry and hi N cut 2-4 times. SNS is Low if no slurry applied in previous years.

Soil Nitrogen Status (SNS)

 Low Mod High

4 Cut 6 week regrowth 68-70D
1st Cut 1st 2 wks May 130 105 105
2nd Cut Mid - End June 100 90 90
3rd Cut End Jly - Mid Aug 70 70 55
4th Cut  End Sept -Mid Oct 70 70 55
370 335 305

3 Cut 8 week regrowth Silage 64-67D
1st Cut Last 2 Weeks May 130 130 105
2nd Cut Last 2 Weeks Jly 105 90 90
3rd Cut Last 2 Weeks Sept 90 70 70
325 290 265
Notes
Add or deduct 30N for Very Good or Average grass growth site
Deduct 30N if over 1000ft
Deduct 10-20N at first cut if typical lagoon slurry applied at 1500-3000 gal per ac
Apply All N in 1st 2 weeks of March
If cutting last week April 1st week May apply all N last week Feb to 1st week Mar at the very latest to High sugar early grass varieties. Do not adopt a very early cutting approach above 1000ft or to late heading or low sugar grass varieties. Permanent old pastures and hi clover swards also have low sugars.
For sulphur fertilisers please go to Testing Grass Page

 

 

SOIL Nitrogen Status (SNS)

Adjusting Nitrogen Fertiliser for Soil Nitrogen Status

SNS Status

Previous grassland Management and nitrogen Usage

Units N previously /ac

High

 Long term grass at high previous N >200

          Grass after grass or I year arable break

          Grass ley in second or later year

Moderate

 a) 1st year Ley after 2 or more years break - last crop pots, beans, peas, legume N/A

b)  Long term grass at moderate previous N 80-200 or hi clover >30% Sward

          Grass after grass or 1 year arable break

          Grass ley in second or later year

Low

 a) 1st year ley after 2 or more years break  - last crop cereal - linseed N/A

b) Long term grass at low previous N < 80 or low clover

          Grass after grass or 1 year arable break

          Grass ley in second or later year
Notes
Reduce SNS by 1 class if the previous sward or year was frequently cut for silage
Increase or decrease SNS by 1 Class if less or more than 120 units N applied as manure in previous years.

 

Nitrogen from Organic Manures and slurries

Application Period 

 Autumn (Aug-Oct) Winter Applied (Nov-Jan) Spring (Feb-Apr)

Rainfall following application 

 500mm or 20" falling to Mar 200mm or 8" falling to Mar Or Summer Applied  

Incorporated - or Not 

 Nil Plough Injection Nil Plough Injection Nil Plough Injection
   6hrs 10-12"    6hrs 10-12"    6hrs 10-12"
Slurries DM% Total N 3000gal
Kg1000L Units/ac Available Nitrogen to the growing crop units per acre
Dairy Cow 2 2 41 4 4 2 16 18 14 20 22 24
6 3 81 6 8 4 24 28 24 28 36 41
10 4 108 5 8 5 16 32 27 22 38 49
Beef 2 1 27 3 3 1 11 12 9 14 15 16
6 2 62 4 6 3 19 22 19 22 28 31
10 4 95 5 7 5 14 28 24 19 33 43
Liquors
Dirty Water <1 0.3 8 2     5     6    
Strainer Box 2 2 41 4 4 2 16 18 14 20 22 24
Weeping Wall 3 2 54 5 5 3 22 24 19 27 30 32
Mechanical Separator 4 3 81 8 8 4 32 36 28 41 45 49
Notes
Typical rainfall during Oct to Mar Incl is 55-60% of the annual implying for most areas 20" average Nov-Mar
Very little N is left from surface applications in the Autumn, and approx 15-25 units from dairy slurry in Winter
No thick slurry applications should be made Feb onwards as these may affect silage fermentation

 

Grass Growth Class

Is assessed from a knowledge of soil type, depth, and April to September Rainfall

Soil Available Water Capacity (AWC)

Rainfall April - September

 St.Ives Falmouth Newquay Fowey Bude
For the most part, rainfall on Cornwall's medium textured loam soils puts them into an average to good grass growth class.  These growth classes can be reduced by one class above 300 m - 1000ft due to exposure & temperature.
Medium soils by texture are loams - mixtures of sand silt & clay.  Apart from dune sands, valley bottoms and Culm measures virtually all Cornish soils vary from very fine sandy loam to silty clay loam and are thus classed MEDIUM < 300mm 3-400 > 400 409 419 387 409 373
< 12" 12-16" > 16" 16 16 15 16 15

AWC Class

Soil type & depth

Growth Class
Low Light Sand Soils and shallow soils Predominantly extreme  Hillsides less than 15" deep Very Poor Poor Average Poor - Ave Poor - Ave Poor - Ave Poor - Ave Poor - Ave
Medium Medium Soils &  deep clay Soils Majority of Soils in Cornwall are over 15" deep - before hitting TRUE bedrock Poor Average Good Ave- Good Ave- Good Ave- Good Ave- Good Ave- Good
High Deep Silty soils, peaty soils, and soils with groundwater Flat Valley Bottoms well drained Average Good Very Good Good -VG Good -VG Good -VG Good -VG Good -VG