The first form of farming that humans developed is known as extensive horticulture. Before a plot of land can be cultivated for the first time, the trees and vegetation must be cleared away, an arduous task usually done by men. Sometimes, a strategy called slash and burn is used, which involves cutting down the trees and shrubs and burning the rest to the ground, then tilling the ash into the soil as fertilizer. Using digging sticks and hoes, horticultural farmers cultivate the top layer of soil before they sow. As seedlings sprout, they water them and feed them with natural fertilizers such as animal dung, and they weed the gardens regularly. Horticultural societies plant not just one crop but many. They have learned that certain plants are “friends”—that is, they enhance one another’s growth—and so they plant these crops side by side. This is practice is known as intercropping. For instance, in Mesoamerica, squash, corn, and beans were planted closely together in flat-topped mounds, a combination known as the “three sisters.” Several corn plants were planted first, in the center of the mound. Once the corn seedlings were well established, squash and beans were planted at their base. As they grew, the corn plants provided stalks for the vining bean plants to climb. The bean plants contributed nitrogen to the soil, fertilizing the other two plants. The squash plants spread across the ground, blocking weeds and protecting the root systems of all three. Typically, societies practicing extensive horticulture have vast knowledge of such sustainable farming methods. These techniques are natural ways to optimize the health and yield of each plant while providing a variable and balanced diet throughout the year. Figure 7.9 In a “three sisters” plot, corn, squash and beans are grown together. Each plant benefits the other. (credit: “Three Sisters” by GreenHouse17/flickr, CC BY 2.0) Incorporating organic methods of fertilization and pest control, horticulture is a sustainable form of farming. Over time, however, this method does deplete the nutrients in the top layer of soil. After a certain number of seasons growing crops on a particular plot, it becomes necessary to let that plot lie fallow. When horticultural farmers let a plot lie fallow, they stop cultivating it and let the grasses and brush grow in naturally, which promotes the accumulation of fresh nutrients in the soil. Plots can be left to lie fallow for as little as one season or as many as 20. While one plot regenerates, the farmer moves on to clear, till, and sow another plot for cultivation. Horticulturalists often have several plots of land in various stages of fallow and cultivation. This method of rotating crops over various plots of land is called extensive or shifting cultivation, as it involves multiple plots over large areas. Horticulture farmers usually have a variety of plots with distinctive soils and climate features, and they tailor specific farming strategies, including crop species, fertilizers, watering methods, and farming-fallow cycles, for each one. Often in horticultural societies, land is not owned as private property but held in trust by family heads or village leaders who allocate plots of land to individuals. People have the right to use the land assigned to them but not to own or sell it, a practice known as usufruct rights. These rights to use certain plots are passed down through families, via either the father or the mother. When newcomers move into an area, they may approach the leader to ask for plots of land to farm. In many African societies, it is also common for people to loan out their plots to one another in gestures of friendship and mutual aid. Extensive horticulture typically provides enough resources to support extended-family households, perhaps with a bit left over to sell in local markets. This amount left over after the needs of the family are met is called surplus. The modest surplus of horticulturalists is sometimes accumulated by families or village leaders in silos or other structures, held in safekeeping for community use in the lean months before the next crops can be harvested. Horticulture does not usually generate enough surplus to support groups of people who do not farm. Craftspeople, religious specialists, and group leaders must all carry on farming alongside these other important activities. Extensive horticulture provides a good way to cultivate crops on land that is not particularly rich with nutrients. Tropical climates tend to have such soils due to the lack of winter dormancy. In temperate zones (23 to 66 degrees latitude), vegetation dies off in the autumn, depositing dead matter into the soil, which then decomposes into a rich substance called humus (hyoo-mus). Humus is essentially built-in fertilizer, feeding new plants as they grow in spring and summer. Because vegetation does not ever die off in tropical areas, tropical soils do not accumulate humus to the extent that temperate soils do. With less humus, it is more advantageous to use a plot of land a few times, then let the natural vegetation grow back. Slashing and burning regrowth is a way for tropical farmers to mimic the natural die-off of vegetation in temperate climates. In climates with warm and cold seasons, the layer of humus-rich soil is much denser and thicker than in tropical regions. In these areas, it is advantageous to dig deeper to prepare soils for sowing, distributing the layer of humus into a thicker layer of soil to serve as a reservoir of nutrients for the new plants. The seasonal deposit of nutrients in the soil also happens in areas surrounding large rivers that flood and recede in a yearly cycle. Along the Nile in North Africa and between the Tigris and Euphrates in the Middle East, ancient farmers were able to use the same soils over and over again as the rivers helpfully dumped organic matter onto their farmlands every year. Riverine farmers learned to control flows of water, creating systems of irrigation to continually water their crops. Sumerian farmers in the Mesopotamian crescent between the Tigris and Euphrates were the first to use the plow, using oxen to pull large blades through their garden plots. Plowing makes the soil even richer for planting. Figure 7.10 A Sumerian plow. Sumerian farmers were the first to use the plow, making possible greater yields. (credit: “John Deere Plow” by Public.Resource.Org/flickr, CC BY 2.0) The use of a plow, the development of irrigation systems, and the continuous cultivation of the same plots are part of a way of farming called intensive agriculture. A good way to remember the difference between extensive and intensive cultivation is to think about how extensive farming involves farming multiple plots over extensive territory, while intensive farming involves applying intensive methods to the same plots over and over again. Intensive agriculture generates much greater yields than horticulture, supporting far larger populations. Greater yields mean greater surplus, which means that societies practicing intensive agriculture generate groups of people who don’t need to farm, such as specialists in craft production, trade, religion, and government. Farmers who practice intensive agriculture focus on a small number of crops, frequently grains or legumes. They use the surplus generated from intensive methods to trade for other foods, tools, and material goods to meet the needs of their households. Most people use the word agriculture to mean plant cultivation of any kind. For anthropologists, however, agriculture is just one form of plant cultivation—the kind involving intensive methods such as plows, draft animals, irrigation systems, and repeated use of plots. This chapter uses the term plant cultivation to refer to both extensive horticulture and intensive agriculture. References to specific types of cultivation use the terms extensive horticulture and intensive agriculture.