At the age of seventeen, Tull matriculated at Oxford, to St. John's College, on 7th July 1691, but appears to have taken no degree. He was admitted as a student of Gray's Inn on 11th December 1693; and called to the Bar on 19th May, 1699. In his admission entry, he is stated to be of two years' standing at Staple Inn, and to be the only son and heir apparent of Jethro Tull, of Howberry in Oxfordshire.

After being admitted as a barrister, Tull made a tour of Europe and, in every country through which he passed, was a diligent observer of the soil, culture and vegetable productions. On his return to England, he married, in 1699, Susannah Smith, of Burton Dassett (Warwickshire). They had two children named after themselves and he settled, with his new family, on his father's farm at Howberry, in the parish of Crowmarsh Gifford, just across the Thames from Wallingford. Determined to improve agricultural methods and increase yields, he pursued a number of agricultural experiments there. By intense application, vexatious toil, and too frequently exposing himself to the vicissitudes of heat and cold in the open fields, he contracted a pulmonary disorder, which, not being found curable in England, obliged him a second time to travel, and to seek a cure in the milder climates of France and Italy. He returned, considerably improved in health, but greatly embarrassed in his fortune. Part of his property in Oxfordshire, he had sold and, before his departure for the Continent, had settled his family on a farm of his own, called Prosperous Farm, in the parish of Shalbourne, near Hungerford. There, he revised and rectified all his old instruments and designed new ones suitable to the different soils of his new farm; and demonstrated the good effects of his horse-hoeing culture. But though Tull was successful in demonstrating what might be done by improved culture, he was not able to turn it to his own advantage. His expenses were enhanced in various ways, but chiefly by the stupidity of the 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.

The drill-husbandry had been probably known and practiced for ages; but was first adopted upon a regular and permanent plan by Tull, who professed to have caught the idea from the vine-culture upon the Continent, and to whose ingenious mind the mechanism of an organ suggested the rudiments of an implement for the delivery of seed in drills. "It was named a drill," he says, "because when farmers used to sow their beans and peas into channels or furrows by hand, they called that action drilling" and it could sew three rows of seeds simultaneously. Later, he devised a horse-drawn hoe to clear away weeds

Tull became a Bencher of Gray's Inn on 5th May 1724. About this time, he was prevailed upon, by some of the neighbouring gentlemen, who were witnesses of the practical utility of his system, to publish his theory, illustrated by an account of it in practice, which he undertook to do, at no inconsiderable expense, and, at a time too, when he was much harassed in his pecuniary affairs. His first publication was a 'specimen' only, in 1731; which was followed, in 1733, by 'An Essay on Horse-Hoeing Husbandry' folio; which was translated into French by Du Hamel.

Tull died at Prosperous Farm on 21st February and was buried, in his native village of Basildon, on 9th March, 1741.