Editing Jethro Tull (agriculturist) (section)

==Work==
In his travels, Tull found himself seeking more knowledge of agriculture. Influenced by the early [[Age of Enlightenment]], he is considered to be one of the early proponents of a scientific – and especially empirical – approach to agriculture. He helped transform agricultural practices by inventing or improving numerous implements.

Tull made early advances in planting crops with his invention of the [[seed drill]] (1701) – a mechanical seeder that [[sowing|sowed]] efficiently at the correct depth and spacing and then covered the seed so that it could grow. Before the introduction of the seed drill, the common practice was to plant seeds by broadcasting (evenly throwing) them across the ground by hand on the prepared soil and then lightly [[harrowing]] the soil to bury the seeds to the correct depth.

At a later period (1730–1740), Tull devoted all his energies to promote the introduction of this machine, "more especially as it admitted the use of the hoe."<ref>[[James Allen Ransome]] (1843) ''The Implements of Agriculture.'' p. 100.</ref>

In his book ''Horse-hoeing Husbandry'' (published in 1731), Tull described how the motivation for developing the seed-drill arose from conflict with his servants. He had struggled to enforce his new methods upon them, in part because they resisted the threat to their position as labourers and their skill with the plough.<ref>Jethro Tull, The New Horse-Houghing Husbandry (1731), p. xiv.</ref>

===Drill husbandry===
[[File:Jethro Tull seed drill (1762).png|thumb|upright|Tull's Seed drill (Horse-hoeing husbandry, 4th edition, 1762<ref>{{Cite book |url=https://archive.org/details/horsehoeinghusba00tull |title=Horse-hoeing husbandry |edition=4th |date=1762 |author=Tull, Jethro |others=Adams, John, 1735–1826, former owner |publisher=London: Printed for A. Millar.}}</ref>)|alt=]]
Tull invented some machinery for the purpose of carrying out his system of drill husbandry, about 1733. His first invention was a drill-plough to sow wheat and turnip seed in drills, three rows at a time. There were two boxes for the seed, and these, with the coulters, were placed one set behind the other, so that two sorts of seed might be sown at the same time. A harrow to cover in the seed was attached behind.<ref name="CWJ 1844 p. 419">"Drill Husbandry" in: ''The Farmer's Encyclopædia, and Dictionary of Rural Affairs'', by Cuthbert W. Johnson, 1844, p. 419.</ref>

Tull also invented a turnip-drill somewhat similar to the other in general arrangement, but of lighter construction. The feeding spout was so arranged as to carry one half of the seed backwards after the earth had fallen into the channel; a harrow was pinned to the beam; and by this arrangement one half of the seed would spring up sooner than the other, allowing part to escape the [[Delia radicum|turnip fly]].<ref name="CWJ 1844 p. 419"/>

When desirable to turn the machine, the harrow was to be lifted and the feeding would stop. The manner of delivering the seeds to the funnels in both the above drills was by notched barrels, and Tull was the first to use cavities in the surfaces of solid cylinders for the feeding. Nothing material in the history of the drill then occurred until 1782.<ref name="CWJ 1844 p. 419"/>

===Growing soil===
Tull considered soil to be the sole food of plants. "Too much nitre," Tull wrote,<ref>''Tull's Book on Husbandry'', p. 13.</ref> "corrodes a plant, too much water drowns it, too much air dries the roots of it, too much heat burns it; but too much earth a plant can never have, unless it be therein wholly buried: too much earth or too fine can never possibly be given to their roots, for they never receive so much of it as to surfeit the plant." Again, he declares elsewhere, "That which nourishes and augments a plant is the true food of it. Every plant is earth, and the growth and true increase of a plant is the addition of more earth." And in his chapter on the "Pasture of Plants", Tull told his readers with great gravity that "this pasturage is the inner or internal superficies ''[sic]'' of the earth; or, which is the same thing, it is the superficies of the pores, cavities, or interstices of the divided parts of the earth, which are of two sorts, natural and artificial. The mouths or lacteals of roots take their pabulum, being fine particles of earth, from the superficies of the pores or cavities, wherein their roots are included."<ref name="CWJ 1844">"Earth" in: ''The Farmer's Encyclopædia, and Dictionary of Rural Affairs'', by Cuthbert W. Johnson, 1844, pp. 428–429.</ref>

Tull wrote with enthusiasm and carried his admiration of the powers of the earth to support vegetation too far; he was deceived, in fact, by the effects of his finely pulverising system of tillage, and did not sufficiently attend to the fact that there are many other substances in the commonly cultivated soils of the farmer besides the earths, and that so far from their being always the chief constituents of the soil, they very often form the smallest portion of even a highly productive field.<ref name="CWJ 1844"/>

That the four earths of which all cultivated soils are composed are all the necessary food or constituents of vegetables has, long since Tull wrote, been decided by accurate investigations of chemists. Of these, lime, either as a carbonate or an acetate or a sulphate, is by far the most generally present in plants; indeed, in one form or another, it is rarely absent from them. The presence of silica (flint) is almost equally general. Magnesia is less usually present, or, at least, it exists in smaller proportions; and the same remark applies to alumina (clay).<ref name="CWJ 1844"/>

===Hoeing by hand===
The operation of hoeing is beneficial, not only as being destructive of weeds, but as loosening the surface of the soil, and rendering it more permeable to the gases and aqueous vapour of the atmosphere. Hoeing, therefore, not only protects the farmer's crops from being weakened by weeds, but it renders the soil itself as more capable of supplying the plants with their food. Tull was the first who inculcated the advantages of hoeing cultivated soils. He correctly enough told the farmers of his time, that as fine hoed ground is not so long soaked by rain, so the dews never suffer it to become perfectly dry. This appears by the plants which flourish in this, whilst those in the hard ground are starved. In the driest weather good hoeing procures moisture to the roots of plants, though the ignorant and incurious fancy it lets in the drought.<ref>Johnson (1844, p. 626).</ref>