My Science School

Although there are thousands of edible plant species, only a relatively small number have been domesticated, i.e. converted to widespread usage by humans. Three crops—wheat, corn, and rice—provide nearly 60 percent of total plant calories that humans consume. Other major crops include potatoes, soybeans, cassava, sorghum, and legumes. The three top crops are grown worldwide, though certain regions are known for specific crops. For example, the United States supplies almost half of the world’s 800 million tons of corn annually, followed by China, Brazil, and Mexico. China, India, and the U.S. are the largest wheat producers, and almost 95 percent of all rice is grown in Asia. And, while 16 percent of total wheat production reaches the world’s markets, rice is primarily consumed where it is grown and only 5 percent makes it to the world market.

Wheat is one of the oldest cultivated crops, beginning around 10,000 years ago in the area known today as the “Fertile Crescent” between the Tigris and Euphrates rivers. Evidence suggests that wheat was used for making bread in Egypt by 5000 BC and its cultivation had spread to Europe by 4000 BC. Although the U.S. is the third largest wheat producer in the world, large-scale cultivation did not begin until the late 1800s when European settlement moved into the central plains. Today, approximately 700 million tons of wheat are grown annually around the world.

Rice continues to be a critical staple for nearly half of the world’s population, and for whom rice cultivation is the sole or primary source of food. Although rice is a good carbohydrate source, it does not provide adequate nutrition—an issue of increasing concern in the developing world where almost three billion people obtain most of their daily nutrients from rice. These populations can suffer from micronutrient deficiencies, most notably a lack of vitamin A.

Corn (or maize) is thought to be a domesticated version of the wild cereal grass teosinte, and was likely cultivated between three and four thousand years ago in Mesoamerica. It is still one of the most common crops grown in the Americas. Only about one percent of the corn that is grown is eaten as whole or processed grain (sweet corn, corn chips, or tamales); more than 50 percent is used as animal feed—primarily for cattle, hogs, and chickens—and the remainder is consumed either as starch or in the form of corn sweeteners. More recently, an increasing amount of land area has been dedicated to growing corn due to the demand for ethanol, a corn-based fuel. In 2007, ethanol production became the second largest use of corn grown in the U.S. The sustainability of this use is controversial.

Arable farming is the growing and harvesting of crops, particularly where the ground is ploughed between harvests, as the term comes from the Latin word for ploughing. Arable farming is of enormous importance to the world's population, since most of us rely on grains or vegetables for our staple foods.

Arable farming means growing crops in fields, which have usually been ploughed before planting. Arable crops are generally annual – they need to be replanted each year.

Land is cultivated (prepared by ploughing) in autumn or spring, and the crop is planted. It grows through the spring and summer, and is harvested in late summer or autumn. The land is then cultivated again for another crop or returned to pasture for one or more years.

Cereal farming requires vast cultivable expanses, a significant labour force and appropriate tools. This method of farming is nonetheless similar to that of market gardening. Ploughing, sowing, fertilising, irrigating and treating are steps that have been followed for thousands of years to ensure an adequate yield and an abundant harvest. Arable farming in industrialised countries now relies on a variety of specialist mechanical devices.

From sowing to harvesting, intensive cereal farming follows a similar chain of events to market gardening, only on a larger scale. Current cereal crops are mostly grown in open fields, whereas tubers, such as potatoes, can also be grown in greenhouses. Both practices require a lot of space and tools, as well as a sizeable workforce. A feature of cereal farming is that it varies according to specific type of soil and way of farming each cereal needs.

The first stage in cereal and tuber cultivation is ploughing. This involves turning the soil over to aerate it, removing residue from former crops and digging furrows. With intensive farming, chemical fertilizers are then applied to the newly ploughed soil, whereas extensive farming relies on the soil’s natural resources and alternates crops on a yearly basis.

Early missionaries were the first to grow wheat and oats in New Zealand. In the first half of the 19th century some North Island M?ori communities grew wheat, which they sold to settlers, exported to Sydney, or used themselves.

New Zealand Company settlements, such as Wellington, Nelson and Whanganui, were intended to be based on arable production rather than animal farming. However, at that stage there was a limited export market for crops, but a huge market for animal products – initially for wool and later for meat and dairy production. Cropping remained important in some areas, particularly the Canterbury Plains and North Otago, where summer conditions were ideal for maturing grain crops.