Wheat is a grass widely cultivated for its seed, a cereal grain that is a worldwide staple food. The many species of wheat together make up the genus Triticum; the most widely grown is common wheat. The archaeological record suggests that wheat was first cultivated in the regions of the Fertile Crescent around 9600 BCE. Botanically, the wheat kernel is a type of fruit called a caryopsis.
Wheat is grown on more land area than any other food crop. World trade in wheat is greater than for all other crops combined. Wheat is an important source of carbohydrates. Globally, it is the leading source of vegetable proteins in human food, having a protein content of about 13%, which is relatively high compared to other major cereals but relatively low in protein quality for supplying essential amino acids. When eaten as the whole grain, wheat is a source of multiple nutrients and dietary fiber.
Nutrition
In 100 grams, wheat provides 1,368 kilojoules (327 kilocalories) of food energy and is a rich source (20% or more of the Daily Value, DV) of multiple essential nutrients, such as protein, dietary fiber, manganese, phosphorus and niacin (table). Several B vitamins and other dietary minerals are in significant content. Wheat is 13% water, 71% carbohydrates, and 1.5% fat. Its 13% protein content is mostly gluten (75–80% of the protein in wheat).
Wheat proteins have a low quality for human nutrition, according to the new protein quality method (DIAAS) promoted by the Food and Agriculture Organization. Though they contain adequate amounts of the other essential amino acids, at least for adults, wheat proteins are deficient in the essential amino acid lysine. Because the proteins present in the wheat endosperm (gluten proteins) are particularly poor in lysine, white flours are more deficient in lysine compared with whole grains. Significant efforts in plant breeding are being made to develop lysine-rich wheat varieties, without success as of 2017. Supplementation with proteins from other food sources (mainly legumes) is commonly used to compensate for this deficiency, since the limitation of a single essential amino acid causes the others to break down and become excreted, which is especially important during the period of growth.
$100 g \ (3 \frac{1}{2} oz)$ of hard red winter wheat contain about $12.6 g$ of protein, $1.5 g$ of total fat, $71 g$ of carbohydrate (by difference), $12.2 g$ of dietary fiber, and $3.2 mg$ of iron (17% of the daily requirement); the same weight of hard red spring wheat contains about $15.4 g$ of protein, $1.9 g$ of total fat, $68 g$ of carbohydrate (by difference), $12.2 g$ of dietary fiber, and $3.6 mg$ of iron (20% of the daily requirement).
Crop development
Wheat normally needs between 110 and 130 days between sowing and harvest, depending upon climate, seed type, and soil conditions (winter wheat lies dormant during a winter freeze). Optimal crop management requires that the farmer have a detailed understanding of each stage of development in the growing plants. In particular, spring fertilizers, herbicides, fungicides, and growth regulators are typically applied only at specific stages of plant development. For example, it is currently recommended that the second application of nitrogen is best done when the ear (not visible at this stage) is about 1 cm in size (Z31 on Zadoks scale). Knowledge of stages is also important to identify periods of higher risk from the climate. For example, pollen formation from the mother cell, and the stages between anthesis and maturity, are susceptible to high temperatures, and this adverse effect is made worse by water stress. Farmers also benefit from knowing when the ‘flag leaf’ (last leaf) appears, as this leaf represents about 75% of photosynthesis reactions during the grain filling period, and so should be preserved from disease or insect attacks to ensure a good yield.
Several systems exist to identify crop stages, with the Feekes and Zadoks scales being the most widely used. Each scale is a standard system which describes successive stages reached by the crop during the agricultural season.
小麦（学名：Triticum aestivum L.）是小麦属植物的统称，代表种为普通小麦，是禾本科植物，也是一种在世界各地广泛种植的谷类作物，小麦的颖果是人类的主食之一，磨成面粉后可制作面包、馒头、饼干、面条等食物，发酵后可制成啤酒、酒精、白酒（如伏特加），或生物质燃料。
种类
小麦籽粒的皮色划分
按照小麦籽粒皮色的不同，可将小麦分为红皮小麦和白皮小麦，简称为红麦和白麦。红皮小麦（也称为红粒小麦）籽粒的表皮为深红色或红褐色；白皮小麦（也称为白粒小麦）籽粒的表皮为黄白色或乳白色。红白小麦混在一起的叫做混合小麦。
小麦籽粒的粒质划分
按照籽粒粒质的不同，小麦可以分为硬质小麦和软质小麦，简称为硬麦和软麦。硬麦的胚乳结构为紧密，呈半透明状，亦称为角质或玻璃质；软麦的胚乳结构疏松，呈石膏状，亦称为粉质。就小麦籽粒而言，当其角质占其中部横截面1/2以上时，称其为角质粒，为硬麦；而当其角质不足1/2时，称其为粉质粒，为软麦。对一批小麦而言，按中国标准，硬质小麦是指角质率不低于70%的小麦；软质小麦是指粉质率不低于70%的小麦。
按照播种季节分类
按照播种季节的不同，可将小麦分为春小麦和冬小麦。春小麦是指春季播种，当年夏或秋两季收割的小麦；冬、麦是指秋、冬两季播种，第二年夏季收割的小麦。