Free The Knowledge: How to Rebuild Our World From Scratch by Lewis Dartnell Page B

The bottom band is the coarse-grained sand component of the soil, the middle layer is silt, and the very top layer holds the finest clay particles, allowing you to visually judge their proportions in the mixed soil.
    The ideal kind of soil for farming is known as loam and is a balanced mixture of roughly 40 percent sand, 40 percent silt, and 20 percent clay. A sandy soil (more than two-thirds of the total) drains well and so is good for wintering cattle, as it won’t get trodden into a quagmire, but minerals and fertilizers are easily washed out and require extra manure. On the other hand, a heavy clay soil (more than a third clay particles and less than half sand) is physically hard to work with plows and harrows, and will require more liming to maintain a healthy crumbly structure.
    Wheat, beans, potatoes, and rapeseed (the source of canola oil) all grow superbly well in well-managed clay soils. Oats thrive in heavier, damper soils than are suitable for wheat or barley, such as the soils of Scotland created by the grinding sweep of glaciers in the last ice age. Historically, oats and potatoes have allowed people to achieve high yields and settle areas where other crops do not grow. Barley prefers lighter soils than wheat, and rye will grow in poorer, sandier soils than other cereals. Sugar beets and carrots also grow well in sandy soils.
    Being lucky enough to find fertile loam soil in a well-drained region is only the start for rebooting agriculture. In order to give your crops the best chance of success, you’re also going to need to physically work the ground. Tillage is the name for all the mechanical effort you need to put into loosening hard soil, controlling weeds, and preparing a receptive layer of topsoil (tilth) for sowing the seeds.
    On a sufficiently small scale, you could get by with very rudimentary handheld tools. A hoe will do an admirable job of breaking up the topsoil and mixing in manure or green fertilizer (rotting vegetative matter) before the growing season, as well as chopping up weeds before sowing and at intervals as the crop grows. A simple dibber stick can be used to poke shallow holes in the ground with regular spacing to drop seeds into and rebury with your foot. But it’s backbreaking, time-consuming work, and you’d have little opportunity for doing anything else. The history of agriculture over the millennia has been a story of improving designs of farm equipment to perform these essential functions more efficiently, to maximize the productivity of the land while minimizing the labor needed.
    SIMPLE FARMING TOOLS: HOE (A), DIBBER (B), SICKLE (C), SCYTHE (D), THRESHING FLAIL (E).
    The iconic implement of agriculture is the plow, but its role has actually changed since the beginning of cultivation. In the fertile, easily cultivable soils of Mesopotamia, Egypt, and China, where agriculture was first developed, the primitive plow was little more than a sharpened log jabbed into the ground at an angle and hauled through the soil by oxen or human laborers. The intention was to gouge ashallow trench that seeds could then be dropped into and lightly buried. In most of the arable land on the planet, however, the soil needs a bit more preparation to make agriculture productive. Nowadays, the function of a plow is to carefully scoop up the uppermost layer of soil across an entire field and flip it upside down, crumbling it slightly. The primary aim of this process is weed control. Before sowing your crop on the land, undesired plants are sliced from their roots and unceremoniously covered with soil. Hidden from the sunlight, they wither and die, and their seeds are buried too deeply to successfully germinate. This cultivation of the land also helps mix organic matter and nutrients into the topsoil, particularly if you’re plowing in manure, and improves drainage of the ground as well as aeration to benefit the soil microbes.
    AGRICULTURAL EQUIPMENT: PLOW, HARROW, SEED DRILL. INSET: THE ACTION OF THE