Broadbalk

Local identifier
R/BK/1
Years operational
1843— (Establishment period end: 1851)
Objective
The aim of the experiment was to test the effect of different organic manures and inorganic fertilizers on the yield of winter wheat.
Description
Started in 1843, Broadbalk is one of the oldest continuous agronomic experiments in the world. Wheat is grown every year on all or part of the experiment. Established to test the effects of various combinations of inorganic fertilizers (N, P, K, Na and Mg) and organic manures on the yield of winter wheat, many of these treatments continue today. A control strip has received no fertilizer or organic manures since 1843. It was started by Lawes and Gilbert in autumn 1843, and the first crop was harvested in summer 1844.
Farm operation data?
Sample archive?
Samples available?
 
Data Access Statement
Available online with registration
Data license
CC BY
Data policy
Yes (not online)
Organization
Rothamsted Research
research organisation
People
Dr Andy Macdonald
principal investigator
Rothamsted Research
Sustainable Agricultural Systems
Dr Sarah Perryman
data manager
Rothamsted Research
Computational and Analytical Sciences
Dr Margaret Glendining
data manager
Rothamsted Research
Computational and Analytical Sciences

Site: Broadbalk

Type
research station field
Local code
R/BK/1
Location
Harpenden
Hertfordshire
United Kingdom
Geographic location
51.80946, -0.37301
© OpenStreetMap contributors
Elevation
130 Metres
Visits permitted?
Yes
Visiting arrangements
Contact Dr Andy Macdonald
History
The first experimental crop was harvested in 1844 after a rotation of turnips (dunged) 1839, barley 1840, peas 1841, wheat 1842 and oats 1843. The last four crops being entirely unmanured. The field was therefore considered to be exhausted according to contemporary practice.
Management
The site is managed using conventional tillage and pesticide applications are applied as necessary, except for herbicide and fungicide exclusion plots. The plough layer (0-23 m) is limed when necessary to maintain a minimum soil pH of 7.0 – 7.5.
Soil type
luvisol
Soil description
The soil is classified as a Chromic luvisol. The soil texture is described as clay loam to silty clay loam over clay-with flints. The soils contain a large number of flints and are slightly calcareous. Below about 2m depth the soil becomes chalk. The experiment is under-drained and the site is free draining. There is considerable variation in soil texture across the site, with clay contents ranging from 19 – 39%
Soil properties
VariableDepthValue (range)UnitsRef yearEstimated?Baseline?
sand content0 – 23 Centimetres25 Percent
silt content0 – 23 Centimetres50 Percent
clay content0 – 23 Centimetres25 (19 – 39) Percent
soil organic carbon0 – 23 Centimetres1 Percent1843
total soil nitrogen0 – 23 Centimetres0.11 Percent1843
plant available phosphorous (Olsen P)0 – 23 Centimetres10 milligram per kilogram1843
soil bulk density0 – 23 Centimetres1.25 gram per cubic centimetre1843
soil organic carbon0 – 23 Centimetres28.8 tonnes per hectare
Climatic type
temperate oceanic climate
Climate description
Mean annual temperature 9.8 degrees C (1981-2010 mean)
Climate properties
VariableTime periodValue (range)Units
annual total precipitation 1981 – 2010 733 (515 – 973) mm
annual mean air temperature 1981 – 2010 9.8 degree Celsius

Design period: Early period (1852—1925)

Design Type
Demonstration strip design
Design description
The experiment was divided into different Strips or 'Plots' (2 - 20) receiving the different fertilizer and manure treatments each year. Most treatment strips were established by 1852, except for strip 2a (2.1), which began in 1885, and strip 20, which began in 1906. Plot 19 was originally a half plot, and became its current size in 1904. Between 1894 and 1925 many plots were harvested in two halves, Top (T) and Bottom (B), equivalent to the Western and Eastern parts of the experiment.
Number of plots
19
Number of harvests per year
1
Crop
CropYears grown
winter wheat
Factors
nitrogen fertilizer exposure
Inorganic nitrogen fertilizer in various forms and amounts applied annually
Plot application: Whole plot
N1  (48 kgN/ha)
1852—1925
Applied to crop: winter wheat
Application method: broadcast application method
Chemical form: ammonium sulfate
All applied in autumn, 1852-1877, all applied in spring 1878-1883; 24 kgN applied in autumn, remainder applied in spring 1884-1925
N1*  (48 kgN/ha)
1852—1925
Applied to crop: winter wheat
Application method: broadcast application method
Chemical form: sodium nitrate
All applied in spring, as one application until 1898, as two equal amounts 1899-1925
N1.5  (72 kgN/ha)
1852—1878
Applied to crop: winter wheat
Application method: broadcast application method
Chemical form: ammonium sulfate
Applied to Plot 19 with rape cake, All applied in autumn
N2  (96 kgN/ha)
1852—1925
Applied to crop: winter wheat
Application method: broadcast application method
Chemical form: ammonium sulfate
All applied in autumn, 1852-1877, all applied in spring 1878-1883; 24 kgN applied in autumn, remainder applied in spring 1884-1925, except to strip 15. Strip 15 N applied in spring 1873-77, N applied in autumn 1878-1925.
N2*  (96 kgN/ha)
1852—1925
Applied to crop: winter wheat
Application method: broadcast application method
Chemical form: sodium nitrate
All applied in spring, as one application until 1898, as two equal amounts 1899-1925
N3  (144 kgN/ha)
1852—1925
Applied to crop: winter wheat
Application method: broadcast application method
Chemical form: ammonium sulfate
All applied in autumn, 1852-1877, all applied in spring 1878-1883; 24 kgN applied in autumn, remainder applied in spring 1884-1925
N4  (192 kgN/ha)
1852—1864
Applied to crop: winter wheat
Chemical form: ammonium sulfate
All applied in autumn
FYM exposure
FYM from cattle
farmyard manure  (35 t/ha)
1843—1925
Applied to crop: winter wheat
Application frequency: Annual
Applied to plot 2b (2.2) from 1843, and to plot 2a (2.1) since 1885. Plot 2a was a new plot made in 1885. FYM is applied in autumn, supplying approx 225 kgN
phosphate fertilizer exposure
phosphate fertilizer
P  (35 kg/ha)
1843—1925
Applied to crop: winter wheat
Application frequency: annually
Application method: chemical basal application
Chemical form: triple superphosphate
Applied in the autumn, omitted 1915
potassium fertilizer exposure
Potassium fertilizer application
K  (90 kg/ha)
1843—1925
Applied to crop: winter wheat
Application frequency: annually
Application method: fertilizer basal application
Chemical form: potassium sulphate
Applied in the autumn, omitted 1915, 1917-1919
sodium nutrient exposure
sodium fertilizer application
Na  (16 kg/ha)
1843—1925
Applied to crop: winter wheat
Application frequency: annually
Application method: fertilizer basal application
Chemical form: sodium sulphate
Applied in the autumn, omitted 1915
magnesium nutrient exposure
Magnesium fertilizer application
Mg  (11 kg/ha)
1843—1925
Applied to crop: winter wheat
Application frequency: annually
Application method: fertilizer basal application
Chemical form: magnesium sulphate
Applied in the autumn, omitted 1915
rapeseed cake exposure
Organic manure supplying approx 96 kgN
C
1852—1926
Applied to crop: winter wheat
Application frequency: annually
Supplying approx 96 kg N (N2).
Factor combinations
FYM  1885—1925
FYM  1843—1925
Nil  1843—1925
PKNaMg  1843—1925
phosphate fertilizer exposure: P
potassium fertilizer exposure: K
sodium nutrient exposure: Na
magnesium nutrient exposure: Mg
N1 PKNaMg  1843—1925
nitrogen fertilizer exposure: N1  (48 kgN/ha)
phosphate fertilizer exposure: P
potassium fertilizer exposure: K
sodium nutrient exposure: Na
magnesium nutrient exposure: Mg
N2 PKNaMg  1852—1925
nitrogen fertilizer exposure: N2
phosphate fertilizer exposure: P
potassium fertilizer exposure: K
sodium nutrient exposure: Na
magnesium nutrient exposure: Mg
N3 PKNaMg  1852—1925
nitrogen fertilizer exposure: N3
phosphate fertilizer exposure: P
potassium fertilizer exposure: K
sodium nutrient exposure: Na
magnesium nutrient exposure: Mg
N1* PKNaMg  1894—1925
nitrogen fertilizer exposure: N1*
phosphate fertilizer exposure: P
potassium fertilizer exposure: K
sodium nutrient exposure: Na
magnesium nutrient exposure: Mg
N4 PKNaMg  1852—1864
nitrogen fertilizer exposure: N4
phosphate fertilizer exposure: P
potassium fertilizer exposure: K
sodium nutrient exposure: Na
magnesium nutrient exposure: Mg
N2* PKNaMg  1884—1925
nitrogen fertilizer exposure: N2*
phosphate fertilizer exposure: P
potassium fertilizer exposure: K
sodium nutrient exposure: Na
magnesium nutrient exposure: Mg
N1.5 PKNaMg +C  1852—1872
nitrogen fertilizer exposure: N1.5
phosphate fertilizer exposure: P
potassium fertilizer exposure: K
sodium nutrient exposure: Na
magnesium nutrient exposure: Mg
rapeseed cake exposure: C
Measurements
VariableMaterialUnitsFrequencyScaleComment
yield componentswinter wheatt/haannuallyGrain and straw yields at field moisture content. Actual dry matter not measured, assumed to be approximately 85% dry matter.
weight per bushel dressed cornwinter wheatlbannuallyBushel weights can be used to derive Hectolitre weights (HLWT),a measure of grain quality.
soil organic carbonSoil%infrequentlyTopsoil (0-23cm) from soil sampled in 1865, 1881, 1893 and 1914.
soil organic carbonSoilt/hainfreqentlyTopsoil (0-23cm) from soil sampled in 1865, 1881, 1893 and 1914. Calculated from % SOC and soil bulk density; adjusted for changes in bulk density in strips given FYM
soil total nitrogenSoil%infrequentlyTopsoil (0-23cm) from soil sampled in 1865, 1881, 1893 and 1914.
plant available phosphorousSoilmg/kginfrequentlySodium bicarbonate soluble P (Olsen P). Topsoil (0-23cm) from soil sampled in 1865, 1881, 1893 and 1914.
soil bulk densitySoilg/cm3infrequentlyA single mean value for all plots which do not receive FYM and estimated values for plots which receive FYM, based on measurements made in 1865, 1881, 1893 (Dyer, 1902), 1914 (unpublished) and 2000 (Watts et al, 2006).
harvest datewinter wheatannuallyIncludes both cutting and carting date, ie dates crop cut and then removed from the field.

Design period: Middle period (1926—1967)

Design Type
Demonstration strip design
Description
In 1926 the experiment was divided into five sections (I-V) which were bare fallowed in sequence to control weeds, usually one year in five.
Design description
19 fertilizer treatment strips divided into five sections in 1926 (I-V) crossing all the treatment strips. In 1955 Section I was divided into Ia and Ib; Ia in continuous wheat, no fallow, Ib continued in the fallow rotation. In 1955 Section V was divided into Va and Vb. Va continued in the fallow rotation, with no herbicides applied. Vb received lime in 1955, and became continuous wheat with no further fallows from 1959.
Number of plots
19
Number of subplots
5
Number of harvests per year
1
Crops
CropYears grown
winter wheat
fallow
Factors
nitrogen fertilizer exposure
Inorganic nitrogen fertilizer in various forms and amounts applied annually
N1  (48 kg/ha)
1926—1967
Applied to crop: winter wheat
Application frequency: twice
Application method: broadcast application method
Chemical form: ammonium sulfate
24kgN applied in autumn, remainder in spring
N2  (96 kg/ha)
1926—1967
Applied to crop: winter wheat
Application frequency: twice
Application method: broadcast application method
Chemical form: ammonium sulfate
24kgN applied in autumn, remainder in spring
N3  (144 kg/ha)
1926—1967
Applied to crop: winter wheat
Application frequency: twice
Application method: broadcast application method
Chemical form: ammonium sulfate
24kgN applied in autumn, remainder in spring
N1*  (48 kg/ha)
1926—1967
Applied to crop: winter wheat
Application frequency: twice
Application method: broadcast application method
Chemical form: sodium nitrate
Applied in spring as two equal amounts
N2*  (96 kg/ha)
1926—1967
Applied to crop: winter wheat
Application frequency: twice
Application method: broadcast application method
Chemical form: sodium nitrate
Applied in spring as two equal amounts
FYM exposure
FYM from cattle
farmyard manure  (35 t/ha)
1926—1967
Applied to crop: winter wheat
Application frequency: Once a year
Applied to strips 2.1 (2a) and 2.2 (2b). Not applied in the fallow years
Factor combinations
FYM  1926—1965
FYM exposure: farmyard manure
Measurements
VariableMaterialUnitsFrequencyScaleComment
yield componentswinter wheatt/haannuallyGrain and straw yields at field moisture content, approximately 85% dry matter.
weight per bushel dressed cornwinter wheatlbannuallyBushel weights can be used to derive hectolitre weights (HLWT), a measure of grain quality
soil organic carbonSoil%infrequentlyTopsoil (0-23cm) from soil sampled in 1936; 1944 and 1966.
total soil nitrogenSoil%infrequentlyTopsoil (0-23cm) from soil sampled in 1936; 1944 and 1966.
plant available phosphorousSoilmg/kginfrequentlySodium bicarbonate soluble P (Olsen P). Topsoil (0-23cm) from soil sampled in 1936, 1944 and 1966
soil bulk densitySoilg/cm3infrequentlyA single mean value for all plots which do not receive FYM and estimated values for plots which receive FYM, based on measurements made in 1865, 1881, 1893 (Dyer, 1902), 1914 (unpublished) and 2000 (Watts et al, 2006).
soil organic carbonSoilt/hainfrequentlyTopsoil (0-23cm) from soil sampled in 1936, 1944 and 1966. Calculated from % SOC and soil bulk density; adjusted for changes in bulk density in strips given FYM
weed species richnessNot specifiedSpecies occurence, selected plots and selected years for all sections (before herbicides were applied)
harvest datewinter wheatannuallyBoth cutting date and carting date (ie date crop removed from field)

Design period: Current period (1968—)

Description
Two major modifications were made from 1968: i) The division of Sections I to V to create 10 new Sections (0 - 9), so the yield of wheat grown continuously could be compared with that of wheat grown in rotation after a two-year break. ii) The introduction of modern, short-strawed cultivars, which lead to an increase in grain yields and a decrease in straw yields. The old cultivar Squarehead's Master was grown on parts of some plots between 1987 and 1990, enabling a comparison to be made with modern cultivars After the 1968 changes, Sections 0, 1, 8 and 9 continued to grow winter wheat only, whilst Sections 2, 4, 7 and Sections 3, 5, 6 went into two different 3-course rotations (see 1968 cropping details link). In 1978, Section 6 reverted to continuous wheat and the other five Sections went into a five year rotation. Pesticides are applied where necessary, except on Section 6, which does not receive spring or summer fungicides. Herbicides have been used as required since 1964 on all of the experiment, except for Section 8 (old Section VA), which has never received herbicides. On Section 0 the straw on each plot has been chopped after harvest and incorporated in the soil since autumn 1986; on all other Sections the straw is baled and removed. In 1993 Section 9 was re-drained so that water leaching through the soil could again be collected and analysed. Lime has been applied as required since the 1950s to maintain soil pH at a level at which crop yield is not limited. From 2001 P has not been applied to some plots until levels of plant available P decrease to more appropriate agronomic levels. This is reviewed each year.
Number of harvests per year
1
Crops
CropYears grown
winter wheat 1968—
oats 1996—
beans 1968—1978
potatoes 1968—1996
beans 2018—
fallow
maize 1997—2017
Crop Rotations
continuous wheat  1968—
  • 1
    winter wheat
F-W-W  1968—1981
  • 1
    fallow
  • 2
    winter wheat
  • 3
    winter wheat
P-Be-W  1968—1979
  • 1
    potatoes
  • 2
    beans
  • 3
    winter wheat
F-P-W-W-W  1982—1999
  • 1
    fallow
  • 2
    potatoes
  • 3
    winter wheat
  • 4
    winter wheat
  • 5
    winter wheat
O-M-W-W-W  1996—2017
  • 1
    oats
  • 2
    maize
  • 3
    winter wheat
  • 4
    winter wheat
  • 5
    winter wheat
W-W-O-W-Be  2018—
  • 1
    winter wheat
  • 2
    winter wheat
  • 3
    oats
  • 4
    winter wheat
  • 5
    beans
F-P-W  1979—1983
  • 1
    fallow
  • 2
    potatoes
  • 3
    winter wheat
Factors
nitrogen fertilizer exposure
N was applied as calcium ammonium nitrate (Nitro-chalk) between 1968 and 1985. Between 1968-1996 N was applied at the same rate to beans and potatoes. Between 1996-2017 oats did not receive N. Since 2018 Oats receive N at half the normal rate. Between 1997-2017 split N treatments were applied twice to the seedbed and post-emergence.
Plot application: Whole plot
Effect: Direct
N1  (48 kgN/ha)
1968—
Application frequency: annually in mid-April
N2  (96 kgN/ha)
1968—
Chemical form: ammonium nitrate
N3  (144 kgN/ha)
1968—
Chemical form: ammonium nitrate
N4  (192 kgN/ha)
1986—
Applied to crop: winter wheat
Chemical form: ammonium nitrate
N5  (240 kgN/ha)
1985—
Application frequency: annually in spring
Chemical form: ammonium nitrate
N6  (288 kgN/ha)
1985—
Application frequency: annually in spring
Chemical form: ammonium nitrate
N1+1+1  (144 kgN/ha)
2001—
Application frequency: mid-March, mid-April, Mid-May
Chemical form: ammonium nitrate
N2+1 for maize
N1+2+1  (192 kgN/ha)
2001—
Application frequency: mid-March, mid-April, Mid-May
Chemical form: ammonium nitrate
N2+2 for maize
N1+3+1  (240 kgN/ha)
2001—
Applied to crop: winter wheat
Application frequency: mid-March, mid-April, Mid-May
Chemical form: ammonium nitrate
N2+3 for maize
N1+4+1  (288 kgN/ha)
2001—
Applied to crop: winter wheat
Application frequency: mid-March, mid-April, Mid-May
Chemical form: ammonium nitrate
N2+4 for maize
potassium fertilizer exposure
Plot application: Whole plot
K  (90 kgK/ha)
1968—
Chemical form: potassium sulphate
K2  (180 kgK/ha)
2001—2005
Chemical form: potassium sulphate
K*  (90 kgK/ha)
2001—
Chemical form: potassium chloride
phosphate fertilizer exposure
Plot application: Whole plot
P  (35 kgP/ha)
1968—2001
Chemical form: calcium bis(dihydrogenphosphate)
sodium nutrient exposure
Plot application: Whole plot
Na1  (16 kgNa/ha)
1968—1973
Chemical form: sodium sulphate
Na2  (55 kgNa/ha)
1968—2000
Chemical form: sodium sulphate
57 kgNa/ha until 1973
magnesium nutrient exposure
Plot application: Whole plot
Mg  (12 kgMg/ha)
1968—
Chemical form: magnesium sulphate
11kgMg until 1973. 35 kgMg every 3rd year 1974-2000.
Mg2  (24 kgMg/ha)
2001—2005
Chemical form: magnesium sulphate
Plus 60 kg Mg in autumn 2000 only
Mg*  (30 kgMg/ha)
1968—2000
Chemical form: magnesium sulphate
31kgMg as magnesium sulphate until 1973
farmyard manure exposure
Plot application: Whole plot
FYM  (35 t/ha)
1968—
Application frequency: annually in spring
Derived from cattle
Residual FYM
2001—
Plots previously receiving FYM
castor meal exposure
Plot application: Whole plot
C  (96 kgN/ha)
1968—1988
Residual C
Plots previously receiving
Factor combinations
FYM N2 PK  1968—1984
nitrogen fertilizer exposure: N2
farmyard manure exposure: FYM
phosphate fertilizer exposure: P
potassium fertilizer exposure: K
FYM N4 PK  1985—2000
farmyard manure exposure: FYM
nitrogen fertilizer exposure: N4
phosphate fertilizer exposure: P
potassium fertilizer exposure: K
(FYM) N4  2001—
farmyard manure exposure: Residual FYM
nitrogen fertilizer exposure: N4
FYM N2  1968—2004
farmyard manure exposure: FYM
nitrogen fertilizer exposure: N2
FYM N3  2005—
farmyard manure exposure: FYM
nitrogen fertilizer exposure: N3
FYM  1968—
farmyard manure exposure: FYM
Nil  1968—
(P)K(Na)Mg  1968—1973
phosphate fertilizer exposure: P
P not applied since 2000 due to high soil levels, reviewed annually.
potassium fertilizer exposure: K
sodium nutrient exposure: Na1
Applied until 1973
magnesium nutrient exposure: Mg
N1 (P)K(Na)Mg  1968—
nitrogen fertilizer exposure: N1
phosphate fertilizer exposure: P
P not applied since 2000 due to high soil levels, reviewed annually.
potassium fertilizer exposure: K
sodium nutrient exposure: -
Applied until 1973
magnesium nutrient exposure: Mg
N2 (P)K(Na)Mg  1968—
nitrogen fertilizer exposure: N2
phosphate fertilizer exposure: P
P not applied since 2000 due to high soil levels, reviewed annually.
potassium fertilizer exposure: K
sodium nutrient exposure: Na1
Applied until 1973
magnesium nutrient exposure: Mg
N3 (P)K(Na)Mg  1968—
nitrogen fertilizer exposure: N3
phosphate fertilizer exposure: P
P not applied since 2000 due to high soil levels, reviewed annually.
potassium fertilizer exposure: K
sodium nutrient exposure: Na1
Applied until 1973
magnesium nutrient exposure: Mg
N4 (P)K(Na)Mg  1968—
nitrogen fertilizer exposure: N4
phosphate fertilizer exposure: P
P not applied since 2000 due to high soil levels, reviewed annually.
potassium fertilizer exposure: K
sodium nutrient exposure: Na1
Applied until 1973
magnesium nutrient exposure: Mg
N2  1968—2000
nitrogen fertilizer exposure: N2
N4  2001—
nitrogen fertilizer exposure: N4
N2 P  1968—2000
nitrogen fertilizer exposure: N2
phosphate fertilizer exposure: P
N4 PMg  2001—
nitrogen fertilizer exposure: N4
phosphate fertilizer exposure: P
magnesium nutrient exposure: Mg
N2 PNa  1968—2000
nitrogen fertilizer exposure: N2
phosphate fertilizer exposure: P
sodium nutrient exposure: Na2
N1+3+1 (P)K2Mg2  2001—2005
nitrogen fertilizer exposure: N1+3+1
potassium fertilizer exposure: K2
magnesium nutrient exposure: Mg2
N1+3+1 (P)KMg  2006—
nitrogen fertilizer exposure: N1+3+1
potassium fertilizer exposure: K
magnesium nutrient exposure: Mg
N2 PK  1968—2000
nitrogen fertilizer exposure: N2
phosphate fertilizer exposure: P
potassium fertilizer exposure: K
N4 PK  2001—
nitrogen fertilizer exposure: N4
phosphate fertilizer exposure: P
potassium fertilizer exposure: K
N2 PKMg*  1968—2000
nitrogen fertilizer exposure: N2
phosphate fertilizer exposure: P
potassium fertilizer exposure: K
magnesium nutrient exposure: Mg*
N4 PK*  2001—
nitrogen fertilizer exposure: N4
phosphate fertilizer exposure: P
potassium fertilizer exposure: K*
N5 (P)KMg  1985—
nitrogen fertilizer exposure: N5
phosphate fertilizer exposure: P
Applied until 200, reviewed annually since
potassium fertilizer exposure: K
magnesium nutrient exposure: Mg
N6 (P)KMg  1985—
nitrogen fertilizer exposure: N6
phosphate fertilizer exposure: P
Applied until 2000, reviewed annually since
potassium fertilizer exposure: K
magnesium nutrient exposure: Mg
N2 1/2[PK(Na)Mg  1968—1984
nitrogen fertilizer exposure: N2
phosphate fertilizer exposure: P
potassium fertilizer exposure: K
sodium nutrient exposure: Na1
Until 1973
magnesium nutrient exposure: Mg
N[0|1]+3 1/2[PKMg]  1985—2000
nitrogen fertilizer exposure: N3
Applied to strip 17
nitrogen fertilizer exposure: N4
Applied to strip 18
phosphate fertilizer exposure: P
potassium fertilizer exposure: K
magnesium nutrient exposure: Mg
N1+4+1 PKMg  2000—
nitrogen fertilizer exposure: N1+4+1
phosphate fertilizer exposure: P
potassium fertilizer exposure: K
magnesium nutrient exposure: Mg
N1+2+1 PKMg  2001—
nitrogen fertilizer exposure: N1+2+1
phosphate fertilizer exposure: P
potassium fertilizer exposure: K
magnesium nutrient exposure: Mg
C  1968—1988
castor meal exposure: C
N1+1+1 KMg  2001—
nitrogen fertilizer exposure: N1+1+1
potassium fertilizer exposure: K
magnesium nutrient exposure: Mg
N2 K(Na)Mg  1968—2000
nitrogen fertilizer exposure: N2
potassium fertilizer exposure: K
sodium nutrient exposure: Na1
applied until 1973
magnesium nutrient exposure: Mg
N4 KMg  2000—
nitrogen fertilizer exposure: N4
potassium fertilizer exposure: K
magnesium nutrient exposure: Mg
Measurements
VariableMaterialUnitsFrequencyScaleComment
yield componentsAll cropst/haannuallyGrain and straw at 85% dry matter.
hectolitre grain weightwinter wheatkilogram per hectolitreannuallySince 1999 selected plots only
thousand grain weightwinter wheatgramannuallySince 1974 selected plots only
weed species richnessNot specifiedannuallySection 8 only (no herbicides)
soil organic carbonSoilpercentevery five years from 1987Topsoil (0-23cm)
soil total nitrogenSoilpercentevery five years from 1987Topsoil (0-23cm)
plant available phosphorousSoilmg/kgevery five years for 1987Topsoil (0-23cm)
soil bulk densitySoilgram per cubic centimeterA single mean value for all plots which do not receive FYM and estimated values for plots which receive FYM, based on measurements made in 1865, 1881, 1893 (Dyer, 1902), 1914 (unpublished) and 2000 (Watts et al, 2006).
nutrient contentAll cropspercentannuallySelected plots since 1968 % N, P, K, Ca, Mg, Na and S. Grain and straw.
take-all disease incidencewinter wheatannuallySelected plots since 1968. Also eyespot, sharp eyespot and brown foot rot.
harvest dateAll cropsannuallySowing and harvest dates of all crops
earthworm abundanceNot specifiedoccasionalSelected plots, occasional years.

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