Martindale W and Vorst JJ (2004) The Rothamsted long term agricultural experiments

Interface, MPC Research September 2004 Agriculture, food and health
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The Rothamsted Long Term Agricultural Experiments
Wayne Martindale, MPC Research, UK and James J Vorst, Department of Agronomy,
Purdue University, USA
Contents
1. IPNS and the Rothamsted Long Term Agricultural Experiments, lessons in
sustainability
2. The Development of the Rothamsted LTAE's
3. The pioneers of plant nutrition, nutrient cycling and limiting factors
4. The growing fertiliser requirement; production of superphosphate in Victorian
England
5. Broadbalk continuous winter wheat at Rothamsted 1843-current
a. Demonstrating nitrogen is obtained from the soil for crop growth
b. Demonstration of the value of mineral fertiliser with respect to organic manure
c. Demonstration of herbicides and the value of break cropping in cereal
production
d. Demonstrating the nitrogen use efficiency of wheat production
e. Demonstrating nitrate leaching from agricultural systems and providing
evidence of cation exchange in soils
f. Demonstrating the importance of long term monitoring for assessing food
safety
6. Park Grass permanent grass at Rothamsted 1856-current
a. Demonstration of the importance of nutrient and lime interactions
b. Demonstration of the relationship between soil pH and biomass production
c. Demonstration of the specificity of grassland flora under different nutrient and
lime regimes
d. Demonstrating the management of species diversity using grass management
techniques
e. Demonstrating the importance of long term monitoring of grassland for
cadmium accumulation
7. Hoosfield P and K exhaustion land at Rothamsted
8. Geescroft and Broadbalk Wilderness at Rothamsted ecological experiments for land
management
9. Other data from the Rothamsted LTAE's
Copyright Wayne Martindale 2003, Published by MPC Research 2003
This publication is sold subject to the condition that it shall not by way of trade or otherwise, be lent, resold,
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subsequent publisher

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The Development of the Rothamsted Long Term Agricultural
Experiments (LTAE's)
Understanding plant nutrition, nutrient cycling and limiting
factors
The mid-nineteenth century was a time of rapid industrialisation and urbanisation. The
problems faced by a growing population were reflected in Lawes and Gilbert's aim of
understanding crop production so as to optimise the use of plant nutrients and agronomic
techniques. They realised that providing increasing population numbers with sufficient food
supply would require an efficient agricultural industry and this increased efficiency could be
demonstrated by agricultural trials.
JB Lawes, innovator and founder of the
Rothamsted experiments
John Bennet Lawes is the founder of the long term experiments and
the Rothamsted Experimental Station. He was the owner of the
Rothamsted estate that he inherited from his parents. JB Lawes was
tutored at Oxford by a Professor Daubeny who advocated the study
of the effects of plant species associations (allelopathy) and, in part,
inspired Lawes to start the long term experiments to investigate the
value of using crop rotations and organic manures in agriculture.
John Lawes was also one of the the first people to manufacture and patent superphosphate
initially using bones that were reacted with sulphuric acid. Lawes developed the
superphosphate production into an industry which generated a substantial fortune. Lawes
was in many ways the true founder of the mineral fertiliser industry. Although he made his
fortune producing mineral fertiliser he advocated the value of recycling nutrients by rotations
and the efficient use of organic manure in much of his work.
JH Gilbert, experimentalist and founder of the
Rothamsted experiments
Joseph Henry Gilbert was an experimenter and chemist who
provided the technical excellence for the development of Lawes'
programs of agronomic research at Rothamsted. Gilbert was driven
to obtain indisputable proof and experimental data on which the
current agricultural industry is based. Without the technical skill
and perseverance of Gilbert the current understanding of plant nutrition could have potentially
been misguided and incorrect. Gilbert and Lawes worked in partnership for nearly sixty
years. Their work increases in importance as we continue to develop new and optimise
established agricultural land management strategies. Much of their work lays the foundation
of much recent agricultural research and their agronomic studies are as valuable today as they
ever were.

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Rothamsted Manor
This was the home of the Lawes family since the 17th Century until
the early years of the 20th Century when John Bennett Lawes
created the Lawes Trust with £100000. This initial endowment has
provided the productive base for 100 years of plant and crop based
research. The Long Term Experiments are located around the site
of the manor house. the manor itself has extensive gardens that also
contain the first LTAE started by Lawes, a clover experiment sited
on one of the Manor lawns. The Manor and the Rothamsted estate
provided Lawes with the land to develop the agricultural experiments at Rothamsted. The
development of fertiliser factories provided an income to allow research and education to
prosper at Rothamsted. This is clearly demonstrated by the current LTAE's.
The pioneers of plant nutrition, nutrient cycling and limiting
factors
John Bennet Lawes, Joseph Henry Gilbert of Rothamsted and
Justus von Liebig provided the first ideas on N cycling within
cropping systems and the limitation of crop yields by plant
nutrients. Liebig contended that plants obtained nitrogen from the
atmosphere whereas Lawes and Gilbert demonstrated the use of
nitrogen from nitrogenous salts applied to the soil. They provided
intensive scientific debate and inquiry with regard to the efficient
use of plant nutrients in arable and livestock production systems.
Justus von Liebig
The debate on the source of nitrogen for the assimilation of
nitrogenous compounds
Justus von Liebig was a German professor who was a contemporary of Gilbert and Lawes.
The relationship between Liebig and, Lawes and Gilbert was often strained and competitive.
A great contention between Liebig and Lawes and Gilbert at Rothamsted developed as the
Broadbalk continuous wheat experiment was started in 1843. It was concerned with defining
the source of nitrogen utilised by crops for assimilation into nitrogenous compounds. Liebig
stipulated that assimilated nitrogen was obtained mainly from the atmosphere while Lawes
and Gilbert maintained that the soil was the primary source of nitrogen. The Broadbalk data
quickly showed that this was the case although Liebig did not accept the findings for some 20
years or more.
They agreed on little, however, during the course of their careers a significant area of
agreement was found by all three advocating that the source of metabolic energy for livestock
was from fat stored in tissues and not from nitrogenous compounds. Lawes carried out
several livestock feed and manure experiments and agronomic research was interfaced with
that of animal production.

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The growing fertiliser requirement; production of superphosphate
in Victorian England
The growing fertiliser requirement of the new agricultural industry is clearly demonstrated by
the development of superphosphates in England during the mid-nineteenth century.
Phosphate was always likely to be a limiting element for many soils in England. Prior to the
production of phosphate fertilisers the only source of phosphate for many cropping systems
was organic manures.
In the 1830's and 1840's John Lawes and others experimented with reacting bone materials
with sulphuric acid to make the bone phosphate more available to crops. This resulted in the
production of superphosphate for which Lawes had a patent made in 1843. At this time
around 40 000 tonnes of bones were being imported into England with a further 26 000 tonnes
being produced in England each year for industrial uses. Lawes successfully developed the
first fertiliser product with superphosphate, a mixture of calcium phosphate and sulphate, and
developed factories by the River Thames in London for production. Bones were soon
replaced with rock phosphates in the manufacturing process. The diagram and photo opposite
show the stone runners used for crushing bones and rock phosphate at Rothamsted used by
Lawes.
The commercial production of superphosphates and other plant nutrients provided Lawes with
an income with which to develop the Rothamsted LTAE's and maintain the Rothamsted
estate.
The edge runners at Rothamsted that Lawes used to crush bone and rock phosphate
Broadbalk continuous winter wheat at Rothamsted 1843-current
The Broadbalk experiment offers the opportunity for the sustainability of continuous wheat
cultivation and arable rotations to be investigated over 150 years. The experiment was
originally started as a continuous wheat cropping system and some plots are now in rotation
with fallowing or break crops of maize and oats.
Broadbalk provides the opportunity to identify trends in arable husbandry, environmental
change and yield potential for the optimal management of winter wheat. The experiment has
provided many high impact results for the agricultural industry and some of these are
highlighted in this review. These have included;
1. Demonstrating nitrogen is obtained from the soil for crop growth
2. Demonstration of the value of mineral fertiliser with respect to organic manure
3. Demonstration of herbicides and the value of break cropping in cereal production

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4. Demonstrating the nitrogen use efficiency of wheat production
5. Demonstrating nitrate leaching from agricultural systems and providing evidence of cation
exchange in soils
6. Demonstrating the importance of long term monitoring for assessing food safety
Figure 1 Figure 2
Figure 1. Aerial view of Broadbalk with inset views of the plots
Figure 2. Broadbalk from the no fertiliser and PK only plot panning across increasing N
treatments July 2001
The sustainable production potential of IPNS as shown by long
term studies at Broadbalk
A winter wheat experiment 1843-present
Nitrogen, the essential nutrient
The value of nitrogen salts and nitrogenous manures to crop production was essentially
defined by Lawes and Gilbert using initial data from the Broadbalk winter wheat experiment
at Rothamsted. The Broadbalk experiment investigated the nutrient requirements of wheat
alone out of the traditional rotations it was grown in. The experiment compared a FYM
regime with a no manuring, P and K only and progressively increasing N regimes. The data
obtained soon showed that N applied to the soil as inorganic salts of N or FYM was essential
for plant growth and eventual yield in the case of cropping systems. This effectively proved
that plants obtained much of their N requirement from the soil, a view contended between
Justus von Liebig who believed that plants obtained N from the atmosphere and Lawes and
Gilbert who maintained and proved that plants obtained n from the soil. This view of N being
available predominantly from soil sources seems common sense to us now but it remained to
be proven in 1843 at the start of the Broadbalk trial.
The Broadbalk winter wheat early results
The value of organic manure
The value of organic manure was another area that was largely undetermined at the start of
Lawes and Gilberts' experiments. Organic manures had been the principle source of nutrients
in agricultural systems in much of the world for thousands of years. However, the
experiments at Rothamsted showed that in order for mass production of food to develop in

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industrialising nations there was not enough organic manure to supply the nutrient
requirement for many cropping systems. Organic manures were generally obtained from with
rotational systems were grazing of land by livestock and manure storage were extremely
important principles. The Broadbalk experiment and others at Rothamsted showed that
therefore was an increasing requirement plant nutrients other than animal manures. Mineral
fertilisers could supplement this requirement.
The value of organic manures is emphasised in all of the Rothamsted experiments where
yields obtained by the use of organic manures were as good as those obtained with mineral
fertilisers. This was an extremely import aspect of Lawes' work.
Organic manures have also been shown to increase the Soil Organic Matter considerably.
The plots at Broadbalk receiving 35 tonnes/ha FYM have only begun to reach their
equilibrium level of SOM after over 150 years of application.
The value of organic manure at Broadbalk winter wheat with regard to grain yield
Arable rotation and the management of diseases

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The use of rotations for cereal cropping systems has been a relatively recent re-development
since the 1960's. Rotation and break crops such as maize, oats, root crops and oilseeds for
cereal cropping was a return to traditional methods that had been utilised in agricultural
systems prior to industrialised systems of agriculture typical of the post 1940's. Rotation has
the benefit of reducing disease and weed pressures; and recycling of nutrients. Under
continuous cropping of cereals in the 1940's to 1960's it was found that wheat yields would
progressively decline after a high yielding first crop. This phenomena was investigated on
the Broadbalk experiment and the root diseases take all and eyespot were found to be
responsible with the occurrence of these diseases increasing season after season of wheat.
Introducing a break crop that was not a host to the root diseases was found to be an effective
form of controlling the impact of the diseases. This is demonstrated in the data shown. se
The use of break crops of maize and oats at Broadbalk
Environmental knowledge; water quality and Broadbalk
The use of the Broadbalk records for environmental studies has been realised since the
experiment started in 1843 as a means to indicate and predict future regulatory control of
agricultural operations. The use of drainage studies at Broadbalk has had important
implications for the development of current regulatory and policy aimed at protecting ground
and surface waters from agricultural inputs. The drainage studies at Rothamsted have also
been instrumental in developing cation exchange principles first advocated by Professor
Thomas Way in the 1850's.

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The nitrate content of drain water from Broadbalk winter wheat
The efficiency and capacity of agri-systems to utilise N
The soils on Broadbalk have been cultivated in a similar manner for over 150 years resulting
in relatively stable soil organic matter. This has given the opportunity to measure the
efficiency of fertiliser nitrogen use by utilising 15-N isotopic tracer. The data collected have
shown that N is utilised most efficiently approaching the optimal N rate for yield response
and this efficiency can be improved by rotational systems of cropping.
The recovery of fertiliser nitrogen for Broadbalk winter wheat
The food chain and cadmium
The use of long term data to develop facts and information on the dynamics of heavy metal
flow in food systems is particularly important. this has been demonstrated in a number of the
Rothamsted experiments, including Broadbalk, with regard to cadmium contamination of

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food stuffs via phosphoric fertilisers. The long term data sets are important in monitoring
levels of cadmium in produce and developing soil management regimes to limit the uptake of
cadmium by crops. An important way to decrease the bioavailability of many heavy metals
including cadmium is by maintaining soil pH above 6.0 with suitable liming programs.
The cadmium content of grain for Broadbalk winter wheat
Park Grass permanent grass experiment at Rothamsted 1856-
current
The Park Grass experiment demonstrates interactions between species on long-term sward
development with changes in lime and plant nutrient inputs. The trial has been permanent
grass since 1856 and provides a case study for species diversity and responses of natural
grasslands to different agronomic management.
An important finding of the experiment has been to show that the effect of soil pH at Park
Grass and the effect of N, P and K nutrition at Park Grass must be looked at as a whole to
assess the value of a particular management regime. This is a particularly important
consideration when considering indicators of biodiversity and environmental quality. For
example the Park Grass experiment has found that there are key environmental and
biodiversity benefits for plots with a range of management intensities and no one single
management regime is optimal. The experiment has also shown the build up of cadmium in
soil from phosphoric fertiliser is lower than that from aerial deposition and cadmium can be
excluded from herbage by suitable soil pH management.
The experiment has provided many high impact results for the agricultural industry and some
of these are highlighted in this review. These have included;
1. Demonstration of the importance of nutrient and lime interactions
2. Demonstration of the relationship between soil pH and biomass production
3. Demonstration of the specificity of grassland flora under different nutrient and lime
regimes
4. Demonstrating the management of species diversity using grass management techniques
5. Demonstrating the importance of long term monitoring of grassland for cadmium
accumulation

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Park Grass viewed from plot 4/2 d no lime, applied N and P
The sustainable production potential of IPNS as shown by long
term studies at Park Grass.
A permanent grass experiment 1856-present
Lime and nutrient arrays create a mosaic of diversity
The Park Grass experiment provides the opportunity of what can happen to soil pH over 150
years with differential fertiliser and lime applications. The graph shows plots a (limed to
around pH 7), plots b (limed to around pH 6), plots c (limed to around pH 5) and plots d that
have never been limed since 1856. The liming of Park Grass began in 1903. The history of
the Park Grass land is such that these plots have been in permanent grass for at least 450 years
and the unlimed plots have not received any liming applications during this period.
The importance of this data shown is that it demonstrates that soil acidification is a natural
process, acidifying inputs from the atmosphere will lower the pH of soil. This is proven by
the observation that soil pH on the Park Grass plots receiving no lime (plots d) and no manure
are around pH 5, the addition of N at 144 kg/ha has ammonium sulphate to these plots has
decreased the soil pH to 3.4 and it is still decreasing.
The Park Grass experiment thus demonstrates the potential to manage soils using nutrients
and liming materials. The pH of soils not only influences crop productivity through a
multitude of processes but it also influences the mobility of nutrients and pollutants in soils.
The management of soil pH is an important aspect of environmental management and
agricultural production.

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The Park Grass experimental pH and nutrient arrays
The importance of soil pH and nutrient for overall biomass
The influence of NPK nutrients on the biomass of the Park Grass experiment is immediately
apparent in that when full NPK applications are made at all pH's the biomass will increase
dramatically compared to un-manured plots. The increase in biomass on plots with added
nutrients compared to those with no nutrients added is generally a factor of two. There are
significant yield penalties for not maintaining pH around 6 with regard to herbage biomass
yield but the most important determinant of biomass yield is nutrient application. This is not
to say that pH maintenance is of lesser important because; (1), we are dealing with the effect
of pH and nutrients on very different mixed swards on Park Grass for each treatment.
Therefore the plot swards are adapted to different pH's by genotype, phenotype and species
composition; (2), the mobility and bioavailability of nutrients and pollutants, particularly
heavy metals, increase as soil acidity increases. Thus, the maintenance of liming can
influence the quality of herbage produced from the Park Grass plots.

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The biomass yield of the Park Grass plots
Species specific biomass and adaptation
The influence of pH on individual species of plants on Park Grass is dramatic. The graphs
shown here show the distribution of two grasses, A. elatius (hairy oat grass) and H. lanatus
Yorkshire fog). Hairy oat grass is seen to respond extremely well to nutrients but will only
produce good yields at higher pH whereas Yorkshire fog responds to nutrients in a similar
manner but will only produce good yields at low pH. This demonstrates how plant species
will preferentially develop in areas of high or low calcium status depending on species. This
distinction produces very specific environments and plant communities.
There are species of grass that tend to be present on all of the Park grass plots including
Anthoxanthanum odoratum (sweet vernal grass). Studies of this grass have shown that there
is adaptation of this species between different plot conditions even though the plot differences
themselves are only 0.5 metres apart.
The Park Grass plots demonstrate the ability to change species composition and abundance by
managing landscapes using inputs such as mineral fertilisers, farmyard manures and liming
materials. The experiment will continue to show how grasslands can potentially change in
terms of biodiversity and production over long periods of time.

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The biomass yield of the grass Arrhenatheum elatius
The biomass yield of the grass Holcus lanatus
Defining species diversity; survey and assessment
The definition of species diversity is difficult to determine because the assessment of diversity
can be very objective for different individuals. The Park Grass experiment offers the
opportunity to investigate a range of species arrays under different management regimes. The
data shown here demonstrate that addition of nitrogen to grass swards can dramatically
decrease the number of species growing in that sward. On the nutrient impoverished plots
where nitrogen is not applied the number of species present will be in the 40's whereas when
nitrogen is applied this number decreases by some 75% in the data shown here. At low pH

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this decrease in species present is most apparent where plots at the lowest pH and highest
nitrogen application have only two species present, Anthoxanthanum odoratum and Festuca
rubra.
This demonstrates that land managers have the ability to determine species composition
relatively easily and the economic, social and environmental determinants of what actually
develops with regard to species diversity is perhaps the most difficult to control.
The species diversity of the Park Grass plots
Environmental knowledge
The use of long term data to develop facts and information on the dynamics of heavy metal
flow in food systems is particularly important. Heavy metal contamination is particularly
important in terms of production of forages because livestock will accumulate heavy metals
resulting in contamination of produce and poisoning. This scenario has been demonstrated in
a number of the Rothamsted experiments, including Park Grass, with regard to cadmium
contamination of food stuffs via phosphoric fertilisers, atmospheric deposition and organic
manures. The long term data sets are important in monitoring levels of cadmium in herbage
and developing soil management regimes to limit the uptake of cadmium by crops. An
important way to decrease the bioavailability of many heavy metals including cadmium is by
maintaining soil pH above 6.0 with suitable liming programs.

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The cadmium content of herbage from the Park Grass plots
Hoosfield exhaustion land at Rothamsted
P and K sustainability; the lessons of the Hoosfield exhaustion land experiment
The behavior of P and K in soils is complex because large amounts of these nutrients can be
available of varying time scales for all soils. In general there are nutrient pools in the soil for
P and K that are immediately available and then there are pools that are available over
growing seasons, decades and hundreds of years. Knowing how to manage these pools of
nutrients with respect to time scale represents an important management strategy for
productive and sustainable farming. Components of the physical breakdown of soils by
erosion and weathering will be important in releasing P and K from less available pools but
these releases are generally too low to support productive crop production. However, where
land has be extensively manured with mineral or organic fertiliser the long term value of P
and K can be considerable. The Hoosfield P and K exhaustion trials definitively showed that
these nutrients can be released to crops over many decades.

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Geescroft and Broadbalk Wilderness at Rothamsted
The wilderness ecological experiments for land management
The Wilderness experiments were started in the 19th Century, they have become import areas
of ecological research. they provide a series of benchmarks for landscape change and land
management. The wilderness experiments are now mature stands of trees. The Geescroft
Wilderness is more acidic than the Broadbalk Wilderness that would have been limed prior to
be left unmanaged. The increased soil acidity associated with unmanaged soils on these
experiments demonstrates the need to manage land so that it can remain vegetated and
productive.
The wilderness experiments can be used to compare land management practices with regard
to liming, cutting and vegetation cover. The stands of vegetation can also be correlated to
unlimed and umanured plots on the Park Grass experiment where continuous cutting of hay
has occurrred. The Broadbalk Wilderness has specific plots where grazing and cutting has
continued and removal of tree shoots has occurred throughout the experiment. This provides
useful comparisons between different management systems and the resulting vegetation
cover.
The photographs show the grazed and ungrazed areas of the Broadbalk Wilderness and the
current day Geescroft Wilderness.

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Other data form the Rothamsted experiments
This short review only covers the experiments started by Lawes and Gilbert in sparse detail,
the data held by these experiments goes far beyond this review. An example of other data
held by the Rothamsted experiments is shown in this section with the cereal and root crop
trials from the Barnfield experiment. The data on root crop responses to Nitrogen with and
without farm yard manure (FYM) addition are particularly useful because they do
demonstrate the potential benefits of including organic manures into fertiliser
recommendations when they are available.
The experimental data under the ownership of rothamsted also include that from other long
term sites such as those at Woburn and Saxmundham in the south of England. These sites are
on different soils and will experience slightly different weather conditions. The experiments
carried out on these sites will follow the aims and principals of understanding how agronomic
principles can be applied to crop productuion. They will generally follow a similar
experimental design as formulated by Lawes and Gilbert over 150 years ago in that a
combination of research, agricultural practice and communication of results will be central to
their development.

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Acknowledgements and introduction
This brief overview of the Rothamsted Long Term Experiments has resulted from work
carried out in 2001 resulting in the publication of several papers and films.
Much of the data from the Rothamsted trials shown in this talk has been represented using
data from the book by Leigh and Johnston (1994) Long-term experiments in agricultural and
ecological sciences (CABI) .
Many of the original photographs shown here are pictures taken in the Rothamsted archives
by Mr Mike Kerper and Mr Randy Spears of the Agricultural Communication Service at
Purdue University with the assistance of Margaret Harcourt Williams, Archivist at IACR-
Rothamsted.
Photos of the edge runner sketch are from Lawes of Rothamsted (1993) by G Vaughan Dyke,
Hoos Press. The aerial shots and plots shots of Broadbalk were given to me by Professor Jim
Ahlrichs of the Department of Agronomy at Purdue University.
Dr Wayne Martindale received financial support from OECD Co-operative Research
Programme on Biological Resource Management for Sustainable Agricultural Systems to
facillitate writing this review. Professor Jim Vorst received financial support from the Potash
and Phosphate Institute, Growmark Industries, Farmland Industries, Purdue University School
of Agriculture, and PCS Sales, Inc to visit Rothamsted with a filming crew in July 2001
facilitating the development of this review.
This review is published by MPC Research as part of a series of reviews that form an on-
line/multi media collection of agricultural research information for education and professional
use.

Martindale W and Vorst JJ (2004) The Rothamsted long term agricultural experiments

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Martindale W and Vorst JJ (2004) The Rothamsted long term agricultural experiments