Rice, Oryza sativa

Rice is the world’s most important staple food and the most important part of the diet for over two billion people. Unlike wheat and maize, 92 percent of the harvest from this third largest cereal crop is used as food. In so-called wet rice cultivation (80 percent of the area), the irrigated fields are constantly under water. This saves on weed control and produces high yields. However, it produces methane, a fermentation gas that is harmful to the climate.

Rice does not drown!

Rice is an annual plant of the sweet grass family (Poaceae). The height of the rice stalks varies from 30 cm to 1.5 m. They have a unique aeration system at the roots that allows them to thrive in flooded fields – making rice the only grass crop that can do this. The plant forms up to thirty stalks, each bearing a panicle where the fruits form. A rice plant can develop up to 3,000 grains. The grain consists of a seedling, endosperm, aleurone layer, seed coat and pericarp. The silver skin, which is formed from the last three layers, contains most of the vitamins and fat.

There are numerous types of rice with different grains of rice in terms of shape and color. Round grain rice is used for sushi, for example, long grain rice such as basmati rice is particularly popular in Indian cuisine and medium grain rice is cooked for risotto, for example. There are red, white, black, purple, green and brown rice varieties.

Rice can be grown both dry and wet, i.e. flooded. Wet rice cultivation was developed in China around 5000 years ago and was accompanied by the breeding of new varieties. The advantage of wet cultivation is that weeds have no chance to grow, so cultivation requires significantly less labor and yields can be increased. For wet cultivation, the seeds are first sown dry and later transferred to the flooded field. The field must then be evenly covered with around ten centimetres of water. The water must not flow too much or too little, with too much causing erosion and too little leading to algae formation. After around six months, the field is then drained and the rice harvested.

Dry cultivation is the preferred method of growth in mountainous regions in particular, as wet rice cultivation is not possible there, or only possible after terraces have been created. Dry rice cultivation is more widespread in Europe and the USA, where it is carried out using a lot of machinery.

From China around the world: rice conquers the world

The journey of rice began 10,000 years ago in the fertile plains of China. This inconspicuous grain, which today feeds billions of people, was domesticated in China around 10,000 years ago. From here, it made its way across continents and through time. Asia, with its lush fields and mighty rivers, became the home of Asian rice, known as Oryza sativa. This type of rice, which is now grown on over 160 million hectares worldwide, found its main cultivation areas in countries such as China, India and Indonesia. Rice has become the centerpiece of many cuisines and feeds countless people.

Asian rice spread through migration to India and South East Asia. Around 2,800 years ago, Indian immigrants brought rice cultivation to the former Assyrian Empire, which was located in the Mesopotamian region of the Euphrates and Tigris rivers. However, rice was only cultivated there to a limited extent and was mainly used for medicinal purposes. Around 2,400 years before our era, rice was already an important foodstuff in the area of the former Elam and was also cultivated in Babylonia.

But the history of rice does not end here. On the other side of the world, in the warm regions of West Africa, another species developed – the African rice, Oryza glaberrima. This rice, somewhat shorter and rounder than its Asian relative, adapted to the climatic conditions of Africa and was already being cultivated 3,000 years ago in what is now Mali. It is robust, hardy and still an important source of food in countries such as Mali, Senegal and Guinea.

In the 7th and 8th centuries, the Arabs brought rice to North Africa, especially to Egypt, where it developed magnificently in the fertile Nile Valley. As early as the 9th century, rice traveled to Spain via North Africa and found an ideal home in Valencia in particular. In addition to rice, the Arabs also brought millet and oranges to this region. Rice also found its way into Italian cuisine via the Arab route. The first risotto variations were created here in the 16th and 17th centuries.

In the 15th century, Portuguese sailors brought rice from West Africa to Portugal, where they discovered that it grew well in the humid valleys, particularly in the Mondego Valley and the Alentejo. Rice quickly became an important part of Portuguese cuisine and, through colonial trade, found its way into the cuisines of Europe, Africa and South America, where it was integrated into local traditions.

Today, rice is grown worldwide, with 90 percent of cultivation still taking place in Asia.

Staple food, side dish, creative variety

Rice is the most important staple food in the world today and the most important part of the diet of over two billion people. Unlike wheat and maize, 92 percent of the harvest of this third largest grain crop is used as food. However, rice has no vitamin A. This means that parts of the population who mainly eat rice and cannot afford a balanced diet often suffer from deficiency symptoms.

Rice is gluten-free and is therefore suitable for people with gluten intolerance. It provides important carbohydrates, but many vitamins are lost in hulled rice as they are contained in the silver skin that has been removed. It is therefore advisable to use wholegrain rice.

Rice is available in different forms and varieties, including basmati, jasmine, arborio and sushi rice. It is used in many cuisines around the world, e.g. cooked as a side dish, as nasi goreng, in sushi, risotto or paella. Rice is also processed into flour, pasta, waffles, flakes, edible paper, milk, oil or wine.

Rice – a climate offender?

Wet rice cultivation requires large quantities of water; 3,000 – 5,000 liters of water are used to grow one kilo of rice. This leads to groundwater subsidence in many regions. At the same time, wet rice cultivation produces methane, a greenhouse gas. The constant flooding creates low-oxygen conditions. These conditions promote certain microorganisms, the archaea. When these decompose the organic material, methane is produced as a by-product. This greenhouse gas is significantly more harmful to the climate than CO₂. It is assumed that 25 percent of annual methane emissions are a result of wet rice cultivation. Therefore, in order to combat climate change, new variants of cultivation must be sought in the future. One idea is to alternate between flooding and draining rice fields. This can at least reduce methane emissions. In dry farming, methane emissions are very low.

The climate change promoted by rice cultivation also poses a risk to rice cultivation itself. Higher temperatures, more extreme weather events and droughts as well as depleted soils are leading to the loss of old rice-growing areas. The crop losses are already driving many small farmers to fight for their existence. The International Policy Food Research Institute estimates that the global production volume of rice will fall by twelve to fourteen percent by 2050 due to climate change.

Sources

Sodi e.V.: History of Food: Research report on rice. Link.
Nature – International weekly journal of science: Multiple articles about rice. Link.