The Coates Farm Study

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Nitrogen flows in a mixed farm
system The Coates Farm Study
Keith Goulding, Colin Webster, Roger Cartwright
Jason Schadie Rothamsted
John Conway, Kate Warman Katharine Leach Royal
Agricultural College
Steve Jarvis, David Hatch, Debbie Donaghy IGER
North Wyke
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Objectives Phase I 1996-2000

• measure nitrogen inputs, outputs
• and transfers
• quantify major loss pathways
• optimise management strategies to
• sustain productivity and profitability
• whilst minimising losses and
• environmental impact.

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Objectives - Phase II2000-2003

• complete a full 7-year rotation, construct a full
  7-year rotational budget, and confirm leaky
  practices and alternative management options.
• account for the missing N in the N budget.
• investigate the short- and longer-term impact on
  the N balance of the transfer of the dairy herd
  from Coates Farm to Elkstone Farm.

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The Coates Farm System at the beginning of the
project

• Typical 'Cotswold' mixed farm of 244 ha on
• shallow clay-loam soil over limestone, with
• 160 Friesian Holstein dairy cows
• 300 ewes
• 120 ha cereals.
• 4- to 7-year rotation
• first wheat, second wheat, first barley
• second barley and 2/3 years ley, or
• second barley or fodder crop and break
• crop
• Plus long leys and permanent pastures grazed by
• the dairy cattle and sheep.
• A commercial farm

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Coates Farm soils
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Sherborne series

• a spade depth of soil over a dry stone wall

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Inputs, outputs and transfers

• Inputs
• seed, feed, fertilisers, precipitation, NOx and
• NH3 concentrations, N fixation by
  legumes.
• Outputs
• grain, pulses and oilseeds, straw, milk, cows,
• calves, sheep, wool
• leaching, denitrification, (volatilisation).
• Internal transfers
• grass, silage, grazed fodder crops using
• grazing cages, NCYCLE and NFIXCYCLE
• straw, manure, slurry, dirty water
• mineralisation/immobilisation.

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Process measurements

• ammonia fluxes by micrometeorology
• leaching using porous ceramic cups
• denitrification and mineralisation by
• coring/field incubation.

Effect of spatial variation minimised by
establishing one 'farmlet' (120 m x 20 m) in each
of 10 fields in which gt70 of the soil is the
dominant 'Sherborne Series, plus 2 farmlets on a
grazing trial measuring leaching only.
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Small Plot Trials, e.g. effect on losses of
different slurry rates applied to maize
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Mean N flows at Coates Farm as tonnes N, 1996-2000
Fertilizer
Concentrates
Legumes
Seed
Atmosphere
34.5
8.3
0.4
3.3
12.2
grazed grass 15.7
recovered waste 9.2
silage, kale, lucerne, straw 13.9
INTERNAL TRANSFERS
Leaching
Missing
mineralization 39.4
Volatilisation
Denitrification
Product
12.9
8.7
13.5
3.2
20.5
grain, milk, calves, cows, sheep, wool
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Full nitrogen budget for Coates Farm (All figures
kg/ha)
Phase II
Phase I
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Nitrate leaching from 1996-2000
kg N ha-1
ley
fm fall
st
st
st
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Nitrate leaching effects of weather and crop
N leached (kg ha-1)
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The nitrogen budget for Coates Farm before and
after the dairy herd moved
kg N/ha
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Conclusions

• Coates Farm used N as efficiently (45) as any
  mixed farm in the UK.
• In dry years leaching losses were small. In wet
  years, practices such as grazing permanent
  pasture or stubble turnips, and applying manure
  and slurry to forage maize caused very large
  leaching losses, almost 200 kg N ha-1.
• Some reduction in losses could be achieved
  through better
• accounting for N in manures and soil
• weather forecasts that permit better timing of
  farm operations.

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Conclusions (continued)

• Consolidating dairy herds might slightly increase
  the efficiency of milk production but at the
  expense of increased leaching as grassland is
  ploughed.
• The Bottom Line farmers have a genuine
  interest in reducing environmental impact, but
  economics and legislation dominate actions and
  major changes in farm practices and N efficiency.

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Systems comparison
Leaching losses N surplus
(kg N ha-1) 65
143 49
- 17 50
- 43
CFS LIFE (IFM) OFS (Organic)
N balances on the LIFE plots range from -35 to
8 kg N ha-1. Positive balances occur where soil
retains N against leaching and 15N results show
immobilisation dominates over mineralisation.