Jethro Tull and Agriculture 4.0

Jethro Tull Agricultural Pioneer [1]

Oil on canvas mural by Alfred Reginald Thomson, RA, 1955, commisioned by the Science Museum, London, showing the agricultural pioneer, Jethro Tull (1674-1741), demonstrating his most significant invention, the seed-drill. © Science Museum / Science & Society Picture Library

As we begin a new decade maybe it is time to reflect once more. I sense a change in the agricultural field, if you pardon the pun.  For three centuries or more agricultural improvements have been driven by ‘Productivity and Output’ – the world needed feeding, land is finite, improved output was the way forward.  In a new paper by  Klerkx, L., Rose, D. [2]  their abstract outlines this change

“Previous agricultural revolutions were, of course, radical at the time – the first seeing hunter-gatherers move towards settled agriculture (Agriculture 1.0), the second characterised by innovation as part of the British Agricultural Revolution which saw new machines such as Jethro Tull's seed drill (Agriculture 2.0), and the third involving production changes in the developing world with the Green Revolution (Agriculture 3.0)”

Today as Klerkx & Rose continue agriculture is heading into what is being dubbed Agriculture 4.0.  Put simply Agriculture 4.0 is the next step in this series of revolutions, one which sees 

“different already operational or developing technologies such as robotics, nanotechnology, synthetic protein, cellular agriculture, gene editing technology, artificial intelligence, blockchain, and machine learning, which may have pervasive effects on future agriculture and food systems and major transformative potential.”

And yet, with the world population about to hurtle through the 8 billion mark, climate change pressures, pollution and plastics, habitat degradation and soil erosion, in the western world at least at the same time moves are afoot to farm in a more extensive holistic way. Media friendly words like Rewilding grab the headlines and the public imagination. In the last decade new thoughts of how farming can adapt environmentally (which are in truth often the reinvention of historically driven practices) are being developed. Much of this eco-pioneering work is taking place at the 3,500 acre Knepp in Sussex which has since 2001 produced some astonishing results [3]. Elsewhere though farmers are looking at a more holistic approach to feeding those hungry mouths with an eye on provisioning both productive and profitable farming alongside sustainability, enterprises such as mob-grazing or no-till farming [4] . The simple fact however is humanity needs to eat.  

Back in 2015 I took time out from my busy audio recording schedule and made a detour of a few miles, my aim to visit the historical landscape of the agricultural pioneer, Jethro Tull. Going back further, studying agriculture as part of my degree, the history of farming and rural entrepreneurship provided the backbone to perceived modern thinking. Over the years though I left the industry, the discipline of agricultural history and improvement is a topic that has long fascinated me.

Although it may only be five years since I visited Tull’s landscape there is a question is in my mind, where does Tull himself fit as agriculture once more reinvents itself for the modern age?

Let’s turn to the man himself.

Cpyt. Wikipedia

Jethro Tull the gentleman farmer was born in 1674 to a well to do family in the parish of Basildon, Berkshire, made up of the two small out of the way hamlets of Upper and Lower Basildon. Even in 2015 when I visited the church in Lower Basildon where a quite easily overlooked memorial stone lies to Tull, despite its proximity to an ever expanding Reading, these hamlets seem remote and untouched by time.  Tull's exact resting place is uncertain but tradition has it that he lies in a vault under St Bartholomew's Church in Lower Basildon. He died in 1741 at Prosperous Farm in the county of Berkshire. During his 67 years he both battled with ill health and quasi-luddite attitude to his inventions and husbandry practices. His ideas were not generally accepted into everyday agriculture for another 75 years or more. 

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Prosperous Home Farm is today an unassuming southern England 300 acre dairy farm enterprise, but in the Eighteenth Century it was an arable farm, which for the last 30 years of his life Jethro Tull called home. A few miles outside Hungerford in Berkshire until 2014 I regularly drove past this farm hard by the A338 near Shalbourne without taking the time to reflect on this land, land which inspired Tull and changed the shape of western agriculture, and society for ever.

I wonder how many drivers passing by today realise the significance of this small farm to the modernisation of agriculture. What happened here was the culmination of a century of advancement, but here (and at Crowmarsh Gifford thirty or so miles away) in a little piece of rural England the first true mechanical farming machine was developed. A moment in history which it could be argued directly aided the Industrial Revolution and fed a human population explosion in Western Europe. Stability in agricultural output allowed massed food production, which in turn fed the nation driven on by the Industrialisation of that nation, or nations. For me the arrival of the horse drawn seed drill and other equipment invented by Tull is on a par with the invention of the motor car, aeroplanes and space travel. It changed the world forever.

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Thirty odd miles north east of Prospect Farm likes the village of Lower Basildon, and down a small track St Bartholomew's Church. Now deconsecrated the interior of St Bartholomew's church offered a cool sanctuary on the very hot summers day when I visited. Yet next to nothing here celebrates Tull. It was a strange feeling walking around outside. I quickly found Tull's memorial stone, leaning against the southern wall. The stone memorial to Jethro Tull was placed here 200years after Tull's death by Gilbert Beale founder of nearby Beale Park. Severely weather-beaten, the writing is now difficult to read; a stone which anyone passing by would ignore as just any other gravestone. How can the memorial to one of the Nation's great pioneers be so obscure?

To the memory of

JETHRO TULL

Pioneer of Mechanized Agriculture

Author of Horse Hoing Husbandry

Baptized in this Church

30th March 1674

Buried here 9th March 1740 *

* Tull died in 1741, but this date is the old calendar date

Entering the lovely church I hoped to find information about Tull within, after all I'd travelled out of my way to visit here. But there was nothing save a few lines in The Churches Conservation Trust leaflet mentioning the memorial stone and that Tull was the 'Father of the Agrarian Revolution'. That was it. And that's a shame.

St Bartholmew's Church, Lower Basildon, Berkshire 2015 Cpyt A Dawes

I first read about Jethro Tull in a children's Encyclopaedia as my interest in farming developed at school. What ignited that spark in me 40 years ago, a young man growing up in northern England, escapes me still. But like the writings of Thomas Hardy that inspired my love of Dorset, reading of Tull and those eighteenth century gentlemen farmers willing to break the rules and force science into the land did, and very much still does, resonate with me.  The seed was sown.

Then, as an aside, as a teenager I discovered the progressive rock band, Jethro Tull.  Tull, or the “Mighty Tull” as Steve Coogan called them in his masterful Saxondale television comedy, have been a part of my life for 40 years or so. Albums such as Songs from the Wood or Heavy Horses, the title track on Tull’s 1978 album of the same name have long inspired me. The band of course was named after the man who three centuries ago lay at the epicentre of the British Agricultural Revolution, pioneered a horse drawn seed drill, dramatically increased agricultural output but is in fact now almost forgotten by  much of society.

Tull's classic work, The New Horse-Houghing Husbandry, details not only his hoeing methods but also the landscape of Prosperous Farm.  This farm is now owned by a Mr Kent who stated in a recent online article;

"We're able to work out which fields are which …. Field shapes and sizes have not changed [since Tull’s time]."

Although the use of the farm has changed it is nice to know that Mr Kent reveres its former guardian of the land. Tull's machinery saw wheat yields increase five-fold during the 18th century. 

"Without that you could not have had the industrial revolution," argued Kent in the article.

And that is what fascinates me about the work of Tull and that of other agricultural pioneers like Charles Townshend, 2nd Viscount Townshend (whose more poetic nomenclature of ‘Turnip’ Townshend was created due to his passion for this humble root crop).  Yes they were wealthy, but they were radical freethinkers in an age of societal constraint.  It feels to me they were ahead of their time by three centuries. 

THE AGRICULTURAL REVOLUTION WAS COMING

The British Agricultural Revolution (Agriculture 2.0 if you like) broke down centuries of inefficient agricultural toil, largely feudal in form, heavily dependent on a peasant labour force to provide food to a largely local market by stint of oxen, hand tools and inefficient use of land. Many fields were open systems such as can still be seen at Laxton in Nottinghamshire, or interestingly resemble modern day allotments which closely follow the open field system of many individuals growing different crops alongside each other with no real plan ,or economy of scale, food production.  Crops were transported no more than a few miles and until 1700 input and techniques to manage the land were rudimentary and often based on centuries old practices. 

True by the beginning of the 18th Century, new science and invention was beginning to tap at the sod of the land, but as they say, old habits die hard. Towns were beginning to expand as rural folk headed into urban areas looking for work. And their citizens they needed feeding. Many have argued it was subsistence farming, but I’m not so sure. My own view is that this farming provided what was needed for what was then a small population. Towns were small and farmers could supply the townsfolk easily as their fields were close by. Agricultural boom and bust years did happen but generally food output matched the needs of the country as a whole.  However this was not a uniform situation. Like allotmenteers of today farmers only grew what they needed but in many cases it was barely enough to tide the village or farm over the lean winter months.

Farmers had long known that removing crops over time reduced productivity, or yield, and that was somehow linked to the soil. But why this was, wasn't fully understood. When farming began, “wildlands” were cleared, crops sown, yields were good for the first couple of years and then dramatically over time reduced until the fields had to be abandoned, or left fallow for years.  This was fine for a small mobile population. Once the land was exhausted that small population either moved elsewhere, or started again in another area they knew, or ate their animals, or sometimes simply starved. The arrival of the Normans during the Conquest changed farming by enhancing the Manorial and Serfedom system, but it was still a hit and miss affair, and not for this commentary.

Everything was dependent on the weather, and the weather defined the harvest. If the latter failed people were hungry, if a succession of harvests failed, the population was in famine. It was lucky then that the Medieval Warm Period was in place, when temperatures were warmer than today, vineyards flourished in southern England and the land was generally able to support the population of 3-4 million.

But from the later Middle Ages onwards settlements grew, these settlements needed and attracted people who slowly began to leave the land to develop trades in town. The town required a stable farming system to feed everyone as the population steadily rose. The best land had already been cleared, more land was needed forcing the cultivation of less productive 'wastelands' like Romney Marsh, the newly drained East anglian fens, upland moors and the Somerset Levels, each with their inherent problems.

CROP ROTATION

In the Medieval Period, generally a two field system existed, otherwise known as crop rotation. Basically half a given area of land produced crops, often autumn sown cereals, until it was exhausted (of soil nutrients) and then returned to fallow while other areas of land was taken out of fallow and cropped, until that became exhausted and so on.  So put simply half of the available land to grow crops was fallow at any one time.  In terms of yield this was totally inefficient by today’s standards. For example wheat output in the early Middle Ages was at around 0.14 tonnes per acre compared to an average of 3 tonnes per acre today.  But by and large farming provided enough food to feed the people; though some estimates put output between 50% and 75% of healthy dietary needs.  From this the three field system developed where among other changes spring sown crops slotted into the regime, making a third of the land fallow at any one time. Productivity was on the up.

However in the middle of all of this had been the catastrophic aftermath of the Black Death era in the fourteenth century. It is estimated that over a fifth of the English population succumbed to this plague. There were simply not enough people to farm the land, and this began a change in agriculture, as less people on the land had to provide enough food, for the recovering population.

Move on a few centuries and we meet the British Agricultural Revolution and Tull. The British Agricultural Revolution of the eighteenth century, it could be argued, began with the arrival into England of the four-field rotation system from Europe, pioneered in Norfolk by the forenamed ‘Turnip’ Townshend.

Emerging science and knowledge of soil fertility and structure at this time developed a notion that with good husbandry three years were optimum to allow an exhausted field to recover enough to be cropped again successfully, and if you grew fodder crops annually livestock could be kept all year, whose waste could be put back on the land. So developing on from the three field autumn sown, spring sown and fallow field system, a fourth field would be needed.  Enter the four field system. This system involved a four year rotation usually of wheat, turnips (a ‘fallow’ fodder crop that allowed for winter feeding of livestock and manure), barley, then clover (to return nitrogen to the soil). Some systems included peas and legumes (again nitrogen), others oats, but the principles were the same. 

Thus on a single piece of land 75% continuous cropping was possible, both cereals and a fodder crop and grazing crop which allowed year round breeding of livestock, and more importantly now only a quarter of land was 'in fallow'. It is only very recently that this system has changed again with the arrival of continuous cropping dependent on high external nutrient inputs via fertilisers and plant science advancement. 

But back to Tull.

In reality many changes and ideas helped accelerate this agricultural revolution, land drainage, horse replacing oxen, enclosures, turnpike roads opening up new markets and readily available writings from leading scientists of the day in mass print for the first time.  But for me what Tull, Townshend and others like Robert Bakewell who developed selective livestock breeding and Coke of Holkham with his sheep management did, was seize the initiative and push forward ideas that only recently had been branded heretical in society. Sound familiar today?

While the others developed new farming practices, what many admire about Tull was his ideas to ‘make it easier and more efficient’ through the development of mechanization. His thinking was absolutely in tune with the embryonic Industrial Revolution gearing up to remove ever greater numbers of rural people away from the land and into the factories of the expanding towns and cities elsewhere in the country.

Developments were already occurring. The predecessor of today’s modern plough with a mouldboard and cutter were developed around 1700 by the Dutch (known as a turn-board  for obvious reasons, it turned the soil). That itself was based on a more ancient Chinese design. More land could now be opened up for agriculture, but that led to problems. Firstly this increasing area needed to have crops sown by hand – literally by hand or later with a seed-fiddle, which was both inefficient and took a lot of time to walk up and down a field.  Secondly once sown into bare land, common weeds could out-compete crops, affecting yields and there was little way of controlling them other than by hand hoeing. The whole system was still inefficient, very labour intensive, a solution was needed.

And this is where Tull in my opinion raises himself a head and maybe a shoulder above others at the time. He experimented, on his own farm which could have led to harvest disaster, new farming techniques and invented mechanical agricultural equipment. He put his money where his mouth was.  Using his knowledge of church organs, he developed a horse drawn machine which could plant seeds in rows down pipes. 

Think about this. Until then people walked up and down fields broadcasting seed corn onto bare ground. Much of this seed corn was eaten by birds and mammals or rotted, before germination. Estimates put it that 1 bushel of wheat seed corn was needed to produce 5 bushels of crop.  I won't detail the mechanics of his seed-drill, but what Tull did was design a drill which allowed the planting the seeds at regular intervals, at a consistent depth, and in a straight line and directly into the soil. This limited waste, allowed for efficient hoeing along the arrow straight lines and dramatically increased harvest yields.

Tull himself said of his invention, 

"It was named a drill because when farmers used to sow their beans and peas into channels or furrows by hand, they called that action drilling." 

Tull's improved drilling method allowed farmers to sow three rows of seeds simultaneously. His other inventions allowed tillage and hoeing between the crops. According to Tull loose soil was vital for good germination and early growth and weed removal increased early growth of the crop. This all seems obvious now, but back then, revolutionary. And Tull was a revolutionary thinker, probably because he wasn’t a farmer at all.

What made Jethro Tull take up farming is not clear.  Being a gentleman by birth, after his education in Oxford, he initially became a musician (an interesting connection to his twentieth century counterpart). Music and agriculture don’t often collide but his understanding of the mechanics needed for an organ to operate led directly to his seed-drill invention. In 1693 he entered Gray’s Inn to study law qualifying as a barrister in 1699, although he never practiced. More importantly for agriculture, at this time he toured the Continent for a few months which gave him at first hand a glimpse of agricultural practices outside England. He then returned home and married Susannah Smith of Burton-Dassett, Warwickshire. 

The farmhouse in Crowmarsh Gifford where Jethro Tull lived and where the development of the seed drill occurred. Cpyt A Dawes.

Tull and his wife settled on one of his father’s farms at Crowmarsh Gifford in Oxfordshire in 1701. Sadly Howberry Farm no longer exists but the house he lived in does, now identified as 16–19 The Street, Crowmarsh Gifford.

I wonder what Tull would think........ the fields he first developed his ideas for increased food production are now built on and permanently removed from food production.

Jethro Tull Plaque, Crowmarsh Gifford. Cpyt A Dawes

It was here in Crowmarsh Gifford that Tull seriously began an almost obsessive determination to improve agricultural methods and increase yields. He ran a number of agricultural experiments, while farming there but a combination of excessive toil and too frequently exposing himself to outdoor work in all weathers meant he contracted a pulmonary disorder. Unable to find relief in England, he went on another tour of Europe, this time to the warmer climates of France and Italy. 

Once again this gave him time to observe European agricultural practices. On his return he moved the family to Prosperous Farm which his father had inherited from a ne'er-do-well uncle, near Shalbourne in Wiltshire (though the farm is in Berkshire). It was here that Tull finally perfected and revised his seed-drill instruments and designed new ones suitable to the different soils of his new farm; here too he demonstrated the good effects of his horse-hoeing culture. All of which made his farm produce more per acre than maybe any in England at the time.

Tradition has it that Tull managed to obtain a sizeable crop off a single field for thirteen years using his methods. In reality this is doubtful and more likely he managed the output with under sowing of clover or legumes and careful management of manuring. Although interestingly Tull wasn't an advocate of animal manures, thinking just the soil particles provided the means of growth, not the nutrients held in the soil as we know today. 

Sadly although Tull developed machines and techniques that have a direct pedigree to machines still being used today, in his lifetime his methods were not readily adopted. 

Despite Tull successfully demonstrating what might be done by improved agriculture, he was not able to turn it to his own advantage. The expense of all this research and development with often failure-afore-success as the result, rose in various ways. Chief among this the unsuitability unskilled workmen employed in constructing his instruments, and in the awkwardness and maliciousness of his servants, who, because they did not or would not comprehend the use of them, seldom failed to break some essential part or other, in order to render them useless. 

In correlation to the Luddites a century later destroying textile machinery, one could guess this was self-interest, seeing a machine do the work of many men could make them lose their jobs. It would be decades later, long after his death, that his vision and tenacity to develop labour saving more efficient machines would be universally adopted.

The seed-drill Tull began inventing in 1701 and developed fully years later has been called the first or earliest agricultural machine because it had internal moving parts which standardised seed sowing and spacing. Its rotary mechanism was the foundation of all subsequent sowing implements.

Unwittingly these inventions and the work of others contributed to the population explosion of the Industrial era due to being able to deliver a fourfold or more increase in the food supply. In England and Wales, the population rose from 5.5 million in 1700 to over 9 million by 1801. By then agriculture was becoming a science based profession. Tull’s and other later techniques were rapidly taken on board by nineteenth century farmers, which along with new food imports from abroad fed the population which more than tripled in a century to over 32 million by 1900.

TULL THE LEGACY

For me as I travelled between Oxfordshire and Berkshire on that hot summer day in 2015 visiting the sites of Jethro Tull’s work, it struck me that his worth is a giant amongst men not just amongst agriculturalists. His name should be up there amongst the Greats who made Britain, Shakespeare, Telford, Nelson, Churchill and so on. His influence on society cannot be underestimated yet I felt as I travelled to Crowmarsh Gifford, Lower Basildon and Shalbourne visiting places and following his life three hundred year earlier, he feels like an insignificant footnote in history. One blue plaque on the house where he lived and an impossible to read memorial stone leaning against the church where he might possibly lie, and a small memorial inside Shalbourne church. And that is about it. Scholars and those interested in agricultural history know his name, but his name is not on the lips of the general public like that of say another mechanical pioneer, Brunel?  I’d suggest more music fans know of Jethro Tull, though how many of these know of the man himself.

I began this commentary with the question. Where does Tull himself fit as agriculture once more reinvents itself for the modern age?  I feel Tull would have approved wholeheartedly of Agriculture 4.0 and I’m sure he’d have been as they say – in the thick of it – maybe not at his own expense this time though.  But what of Rewilding, of mob-grazing and of no till – would that be seen as going backwards maybe in Tull's mind? I think maybe not, and Tull would approve of this change.

George Hosier Farm from its highest point. Cpyt A Dawes

For a number of years I knew a farmer in the same area, just a few miles down the road from Prosperous Farm, George Hosier of Wexcombe [4]. George was one of the first farmers to go over to no-till agriculture in England. A pioneer you may say in the plough-mould of Jethro Tull. I went to visit George's huge and very expensive no-till seed drill from New Zealand, which had to be specially imported.  George began his farming change in 2014 and while it took a while, and worries about weeds and blackgrass aside, the benefits have been positive. Soil structure has improved, earthworm numbers are increasing, and productivity is as one would expect on an arable farm working to conventional inputs. A notable increase in birdlife too and he has stone curlews breeding on his land. And as George said to me the really big saving is we’re only on the fields with the tractors for a couple of weeks a year. No ploughing, no disking, just a one pass seed drill. A huge saving in diesel costs if nothing else. His tractors are satellite GPS driven, almost zero wasted seed and the most efficient coverage of the land with each pass is possible. Technology is king here.

I can imaging Tull being impressed with this efficiency. After all Tull’s ideas and ambitions was to

‘make it easier and more efficient’ through the development of mechanization”.  

Two weeks work on a farm to produce a crop, feels very Tullian (if that is a word). Though of course the reality is of course not just two weeks work a year to get the seed sown and harvested.

But what of the rewilding? What of looking back at ways of being a leading agricultural company, while having enviro-credentials?   I had the privilege of visiting Doves Farm just down the road from George Hozier a few years ago. I’d been longing to go there for some years, not least as Doves Farm actually farms some of Tull’s original Shalbourne land. [5]

Emmer wheat growing on Doves Farm land, with in the background land Jethro Tull farmed, during my visit in 2016. Cpyt A Dawes

Doves Farm today is a highly profitable, nationally available, organic flour producer. Not just flour but ancient grains flower. On land that Tull himself sowed the seeds leading to an agricultural revolution; Doves Farms now grow some of the UK’s lost ancient grains. Rye was the first crop they sowed, and then Spelt, with more ancient Einkorn and Emmer soon following. These naturally low gluten cereals make of course low gluten bread, something many consumers desire today.  Organic they may be but very much high tech too. Inside their factory adjacent to Tull’s fields it is conveyor belts, stainless steel vessels, computer controlled processing and an efficient production system from field to shop. Out on the farm itself, being organic they have seed banks and beetle strips which provide predators for all those pests, though growing ancient varieties of cereals, they are largely disease resistant anyway.  

Doves Farm Beetle Bank Cpyt A Dawes

There again, I could feel the influence of Tull and the Agriculture 2.0 pioneers as I watched Doves Farm’s highly automated, efficient milling and product delivery system. Noisy mind you in the milling shed. But my mind harks back to that summer’s day in 2015 when I stood in front of Prosperous Home Farm. I felt a little sad. Just how many people who pass by on their way to Hungerford to buy a sandwich for lunch know that without Tull’s invention on the land they now pass, what they are buying, bread, provided cheaply and efficiently by today's agriculture, would not be as readily available without his and others of the times invention.  We forget how history plays an important and large part in present day life, not least with every generation managing the land for the nation’s good.

Neatly summed up organic pioneer Robert (Bob) Rodale in "The Regenerative Concept."  [6]

"In short, the whole concept of thorough tillage, row cropping, and keeping the soil surface as bare as possible emerged from the brain of Jethro Tull" 

It is a sobering thought. We rightly applaud Brunel for the railways, Macadam and Telford for the roads and canals, but the railways, roads and canals carried the bountiful harvest of Tull's pioneering mind and inventions, to feed the nation.

I’ll leave the last word to William Macdonald author of ‘Makers of Modern Agriculture’ 

“When it is remembered what a prominent part Agriculture plays in the history of all Nations, it does seem strange that so little is known of the lives of those pioneers who have been foremost in the discovery of fundamental principles, improved methods, and labour-saving machines.”

Selective Footnotes and Further Reading to this Jethro Tull article

[1] The above edited and amended commentary on the agricultural pioneer Jethro Tull,  first appeared as a personal visit to Jethro Tull’s landscape in 2015 on my nature and wildlife blog. 

http://wessexreiver.blogspot.com/2015/07/jethro-tull-agricultural-pioneer.html

[2] Klerkx, L., Rose, D. Dealing with the game-changing technologies of Agriculture 4.0: How do we manage diversity and responsibility in food system transition pathways? Global Food Security, Volume 24, March 2020

[3] Tree I. (2018). Wilding: the return of nature to an English farm. London, UK: Picador. 

[4] Farmerama podcast. No-till and mob-grazing. In this podcast Hertfordshire arable farmer John Cherry talks about his experiences of converting to no-till and mob grazing - with reference to managing black-grass and renewed fertility in the soil. You can hear about the effect it has had on the bottom line even in low-yielding years.

https://www.agricology.co.uk/resources/no-till-and-mob-grazing

[5] Hosier Farms, Wexcombe http://www.wexcombefarm.co.uk/

[6] Doves Farm https://www.dovesfarm.co.uk/

[7] Rodale, Bob, "The Regenerative Concept," Rodale Institute, http://www.rodaleinstitute.org (December 8, 2000).

Further Reading : 

White, C. (2014). Grass, soil, hope. White River Junction, Vermont: Chelsea Green Publishing.

Sayre, Laura L. (2010) The pre-history of soil science: Jethro Tull, the invention of the seed drill, and the foundations of modern agriculture. Vol 35 issues 15-18 Physics and Chemistry of the Earth. Elsevier Ltd. 

Jethro Tull Biography – quick on-line summary of Tull’s life 

http://biography.yourdictionary.com/jethro-tull

Fussell, G. E. (1973) Jethro Tull: His Influence on Mechanized Agriculture, London, Osprey 

Jethro Tull at the American Society of Mechanical Engineers

https://www.asme.org/engineering-topics/articles/history-of-mechanical-engineering/jethro-tull

Profile of the current owner of Prospect Farm, Mr R Kent

http://www.telegraph.co.uk/finance/migrationtemp/2952144/Business-Profile-Renaissance-man-revives-his-career.html

Macdonald, W. (1913) Makers of Modern Agriculture . London, MacDonald 

Available online http://www.gutenberg.org/cache/epub/40670/pg40670.txt