The Knowledge: How to Rebuild Our World From Scratch (8 page)

As a farmer, you have only limited control over nature. You obviously cannot control the amount of sunlight beaming onto your fields: you can’t change the climate of your region or dial in the seasons. You also can’t control the rainfall, although you can regulate the moisture content of your fields by balancing irrigation and drainage. The one thing you have most control over is the soil: you can chemically enrich it with fertilizers, as we’ve just seen, and physically manipulate it with tools like the plow. So the most fundamental element of agriculture under a farmer’s control is the soil, and that requires an understanding of what soil is, and how it supports plant growth.

All the civilizations of history owe their existence to this thin scraping of topsoil. Hunter-gatherers can support themselves by foraging in woodlands, but cities and civilization rely on the enormous productivity of cereal crops—shallow-rooted grasses that are utterly dependent on the resources provided by topsoil.
The basis of all soil is disintegrated rocks that make up the crust of our planet. Rock is physically attacked by flowing water, blowing wind, and grinding glaciers, and chemically weathered by weakly acidic rainwater that
dissolves a little carbon dioxide as it drops from the clouds. Depending on the degree of crumbling, this produces gravels, sands, and clays. These particles are stuck together with humus—a matrix of organic matter that helps retain moisture and minerals, and gives topsoil its dark color. Soils typically contain between 1 and 10 percent humus, although peats approach 100 percent organic matter. But, most important, soil hosts a huge and diverse population of microbial life, an invisible ecosystem that processes decaying matter and recycles nutrients for plants.

The main factor that determines the nature of a particular soil and its appropriateness for different crops is the proportion of different particle sizes: gritty sand, intermediate silt, and fine clay. It’s easy to get a visual check on soil composition. Fill a glass jar one-third of the way with soil (picking out any hard clumps, stems, or leaves) and top it off almost to the brim with water. Screw on a lid, and shake vigorously until all lumps have been broken up and you have a uniform muddy soup. Let the jar stand undisturbed for a day or so, allowing time for the suspension to settle back down and the water to be nearly clear again. The different grains will have sedimented out in order of their particle size to show distinct layers or bands. 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 a
shallow 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 PLOW TO SLICE AND TWIST OVER STRIPS OF TOPSOIL.

Immediately after the cataclysm you’ll hopefully have little trouble finding abandoned tractors and fuel to run them, with trailers sporting multiple plowshares. But once available fuel dries up or lack of spare parts stills the tractor, you’ll have to revert to less intensive methods. And it won’t simply be a case of finding some oxen and harnessing them to the modern plow, as these large multiple-bladed contraptions require enormous traction to rip them through the ground. If you can’t find a traditional plow—perhaps check museums in the nearby deserted cities—you will have to construct your own. You might be able to scavenge a modern plow blade from a trailer rack and remount it singularly on a frame, but if these have all rusted away, you could construct a wooden plow plated with cast iron, or rework scavenged steel panels in a forge. The plowshare is essentially a sharpened blade that horizontally undercuts the soil and forces it up over the moldboard, shaped to carefully roll the sod slice over and lay it back onto the field upside down.

After plowing, the resultant furrows and ridges must be smoothed down to prepare a seedbed ready for sowing. The harrow is as ancient as the plow, and alternative designs differ by how deeply they penetrate and how finely they break up clods for the tilth. Modern harrows use rows of upright metal disks to cut through the ground, or springy curved metal tines that vibrate up and down as they are dragged to pulverize the ground, mechanically mimicking the action of a hand-wielded rake. You can build your own simpler designs of diamond-shaped wooden frames with spikes sticking down, or even drag a heavy tree branch across the surface if you’re really stuck. Different crops prefer particular conditions of tilth; wheat, for example, likes a fairly coarse seedbed, with clods about the size of a child’s fist, whereas barley prefers a much finer tilth. Lighter harrowing is applied after sowing to cover the seeds, and can also be used between cultivated rows to tear up weeds.

Once an appropriate tilth has been prepared, the next step is to put
seeds into the ground. The original meaning of “broadcast”—coined centuries before the invention of radio or TV—is scattering seeds far and wide, tossing them from a sack as you walk back and forth across the field. You can distribute seeds relatively quickly this way, but you have little control over their exact placement, which makes weeding later difficult. But again, with a little bit of ingenuity you can improve this process immeasurably. A seed drill is a mechanical seed sower. At its simplest, a cart has a hopper full of seed on top, and a chain of gears driven by one of its wheels that slowly turns a paddle at the bottom of the hopper chute to release a single seed at regular intervals. Each seed tumbles down a narrow vertical tube to be embedded at its preferred depth in the soil. Multiply the number of paddles and tubes in parallel and you can sow several rows in one pass, and tweaking the gear chain will alter the distance between plants in each row (you’ll find the optimum to use for different crops by experience). This system is much less wasteful of seed because with the optimized spacing, the growing plants do not compete with one another; nor do you waste space with excessive gaps. Moreover, arraying your crops in neat lines, rather than dispersed haphazardly by broadcasting, allows you to more easily weed between the rows. With a little more sophistication, a seed drill can also be constructed to deposit a small dollop of liquid manure or fertilizer into the seed hole, thereby helping every sprout establish itself.

Agriculture is all about exploiting a stage in the life cycle of the plants we’ve adopted as crops. Many plants have adapted a particular part of their structure to act as a storehouse for their captured sunlight energy, to be used either by themselves the following year or as an inheritance for the next generation, their seeds. These stores are precisely the
succulent and nutritious parts that you will be familiar with on the supermarket shelves. Most of the root and stem vegetables we eat are biennials—they bloom in their second year. Their reproductive strategy is to hoard a season’s worth of accumulated energy, stashed away in a specially enlarged section, remain dormant over winter, and then capitalize on their stockpile early the following spring to produce flowers and seeds well ahead of competitors. Examples of swollen taproots include carrots, turnips, rutabagas, radishes, and beets. By cultivating these strains and harvesting the bulging portions, we’re essentially raiding the energetic savings account they’ve diligently built up over the growing season. Potatoes aren’t actually a root vegetable, and the tuber we eat is in fact a swollen section of the stem. Other plants use specialized leaves as their energy storehouse—onions, leeks, garlic, and shallots are all tight clumps of thickened leaves. Cauliflower and broccoli are actually immature flowers and will become inedible if not picked early enough. Fruits are obviously the energy repository for a plant’s seeds, such as the succulent flesh enveloping the pit of a plum; the grain of cereal crops such as wheat is also botanically a type of fruit.

As humanity gave up its nomadic lifestyle and became established in settlements, rooted to a particular locale with surrounding agricultural fields, we became utterly dependent on reliable harvests from the plants we adopted as crops. But we’ve not been content to gratefully accept the nutritious plant stores that natural selection has provided. Over many generations of selective breeding, choosing which plants to propagate on the basis of certain desirable characteristics, we’ve tuned their biology to emphasize certain qualities and diminish unwanted traits. In the process of hacking these plants’ reproductive strategies to subvert them to our own purposes, we’ve distorted their biology so much that they are now as reliant upon us for their survival as we are upon them for our own. Every crop we grow today, from the
grotesquely swollen tomato to the stunted and top-heavy rice plant, is a technology in its own right, the product of ancient genetic engineers.
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THE MOST IMPORTANT CEREAL CROPS: (TOP) WHEAT, RICE, CORN (MAIZE), BARLEY; (BOTTOM) OATS, RYE, MILLET AND SORGHUM.

There is an enormous diversity of edible plant species around the
planet, and even though only a tiny fraction of these have been chosen for cultivation and selectively bred over millennia by civilizations throughout history, there are still an estimated 7,000 cultivated strains. However, only a dozen species account for more than 80 percent of global crop production today, and the major civilizations of the Americas, Asia, and Europe were built on just three staple crops: corn, rice, and wheat, respectively. These three plants will be just as critical to rebooting after the apocalypse.

Corn, rice, and wheat, as well as barley, sorghum, millet, oats, and rye, are all cereal crops: varieties of grass. This dominance of cereals in our diets, coupled with the fact that much of the meat we consume comes from livestock fed by either grazing in pastures or on grain fodder, means that much of
humanity subsists, either directly or indirectly, by eating grass. And it is on this hugely significant category of crops that survivors will need to focus.

While the harvesting of many crops is pretty straightforward and intuitive—potatoes dug out of the sod, onions plucked off the surface, and apples picked from the boughs—getting cereal grain out of the field and processed for the table is a little more involved. Harvesting maize is as simple as walking along the rows with a sack slung to your back and plucking the cobs off the stalks, but the grain of other cereals is more finicky to remove. The no-fuss method is simply to chop down the entire plant and recover the grain away from the field. The tools for reaping are the sickle and the scythe. The sickle is a short curved blade, sometimes serrated, on a handle, and is used to slice through the stalks as the other hand gathers them into bunches. The scythe is a larger, double-handed tool composed of a long pole with two grips and a gently curved blade, around a yard in length, projecting out at a right angle. Wielding a scythe takes more practice, but it is held with straightened arms, and the blade is swept horizontally over the ground in a steady rhythm by smoothly twisting the whole body. The felled stalks are tied into bundles, and these sheaves are leaned upright against
one another to dry in the field, then brought inside barns before the autumn rains.

After collecting the harvest—literally reaping what you sow—the next step is to separate the grain from the rest of the plant. This is called threshing, and the simplest way is to lay the harvest out on a clean floor and beat it with a flail—a long handle with one or more shorter sticks attached at the end with leather or chain hinges. Small-scale mechanical threshers rely on exactly the same basic principle, using a spinning drum covered with pegs or wire loops that fits tightly inside a round casing to strip grain from its stalk as it passes around the gap, and sieve out the grain through a grating at the bottom.

This threshing process leaves all the grain mixed in with the empty husks, and you must now separate the wheat from the chaff (it’s amazing how many everyday phrases derive from agriculture, the only vestigial link many of us retain from our heritage of working the land). The process is called winnowing, and your low-tech option is to simply toss the threshed material into the air on a windy day—the lighter chaff and straw are carried a short distance away on the breeze and the dense grain falls more or less straight back down. Modern machinery creates its own artificial wind using an electric fan, but relies on the same millennia-old principle.

As your post-apocalyptic society recovers and the population grows, one of the most crucial inventions for improving the efficiency of agriculture, producing maximum food with minimum human labor, and enabling a populous city-dwelling civilization is one that integrates these various processes. Combine harvesters today allow a single farmer to process twenty acres of wheat every hour—around a hundred times faster than reaping by hand with a scythe. A horizontal serrated blade mechanically replicates the action of the hand sickle, sawing side to side to cut the stalks as they are dragged over the front of the machine by a large cylinder of rotating paddle arms. The basic design hasn’t changed in almost two centuries, and the first horse-drawn mechanical reapers look surprisingly similar to their modern descendents. The combine harvester is undoubtedly one of the most important inventions of recent history, freeing so many of us from being required to work in the fields and enabling us to perform other roles in a complex society.

RUDIMENTARY MECHANICAL REAPER WITH SWEEPING ARMS (A) AND LOW, SICKLE-LIKE SERRATED BLADE (B).