Introduction to Major Field Crops

Origin

Maize has been cultivated for thousands of years. During archeological excavations in New Mexico, grains of maize and parts of maize ears found in caves and rocks shelter, which are thought to be about 4,500 years old.

Distribution
Although in the first instance maize was grown in the gardens rarely, its value was very soon recognized as a food crop. So maize spread over large area of Spain, Portugal, France, Italy, South Eastern Europe and North Africa in the years following its introduction. The Portuguese brought it to West Coast of Africa in the beginning of 16th century and somewhat later to India and China.

Classification
Maize is an annual plant belongs to family Graminae/Poaceae and the genus Zea. The genus Zea has only one species Zea mays (L.). It is divided into seven groups. The classification is based on largely on the character of the kernels.


1. Flint Corn(Zea mays indurata): The endosperm in this type of maize kernel is soft and starchy in the centre and completely enclosed by a very hard outer layer. The kernels are usually rounded but are sometimes short and flat. Colour may be white or yellow. This is the type most commonly cultivated in India.

2. Dent Corn(Zea mays indentata): Kernels have both hard and soft starches. The hard starch extends on the sides, and the soft starch is in the centre and extends to the top of the kernels.Rapid drying and shrinkage of the soft starch results in characteristicdenting. This is the most common type of maize grown in U.S.A.

3. Pop Corn(Zea mays everta): It possesses exceptional popping qualities. The kernels are usually small and contain an even higher percentage of hard starch than flint corn. When they are heated the pressure buildup within the kernel suddenly results in an explosion and the grain is turned inside out. The corn is used for human consumption as freshly popped maize.

4. Sweet Corn(Zea mays saccharata): Sweet corn contains glassy, sweetish starch. It is characterized by a translucent sweet horny appearance when immature and a wrinkled condition when dry. The ears are picked green for table use and canning. It contains 5.0 per cent sugar as compared to 2.0 per cent in dent and 2.3 per cent in flint type.

5. Floor Corn or Soft Corn(Zea mays amylacea): Floor maize is somewhat similar to Flint corn in plant and ear characteristics. Kernels are composed of entirely of soft starch. They especially develop no dent or only a very small one.

6. Pod Corn(Zea mays tunicata): Pod cornis characterized by having each kernel enclosed within a pod or husk. It belongs to one of the earliest domesticated types and henceit is not grown commercially.

7. Waxy Corn(Zea mays ceretinakulesh): The endosperm of the kernel when cut or broken gives a waxy appearance. The starch is gummy and has some of the characteristics of tapioca. It is now being grown commercially on a small scale to produce starch similar to tapioca starch.


Fig: Types of maize grains.