Early-maturing varieties: spring sowing 80-100 days, cumulative temperature of 2000-2200 ℃; summer sowing 70-85 days, cumulative temperature of 1800-2100 ℃. Early-maturing varieties are generally short plants with a small number of leaves, 14-17. Due to the limitation of fertility period, the yield potential is small.
Medium-maturing varieties: spring sowing 100-120 days, requiring cumulative temperature of 2300-2500 ℃; summer sowing 85-95 days, cumulative temperature of 2100-2200 ℃.
Late-maturing varieties: spring sowing 120-150 days, cumulative temperature of 2500-2800 ℃; summer sowing more than 96 days, cumulative temperature of 2300 ℃ or more. Generally, the plants are tall and have many leaves, mostly 21-25. Because of the long reproductive period, the yield potential is larger. 1. Hard-grain type: also called flint type. Seeds are mostly square-rounded, the top and around the endosperm are horny, only the center near the embryo part of the powder, so the appearance of translucent and shiny, hard and full. The color of the grains is mostly yellow, with occasional by, red, purple and other colors. Seed quality is good, is a long time in China cultivated more types, mainly for food grain.
2. Horse-tooth shape: also called horse teeth type. Seeds flattened rectangular, because the top of the powder than the sides of the horny dry faster, so the top of the center concave, shaped like a horse's teeth, so the name. Seed skin wrinkles rough opaque, mostly yellow, white, a few purple or red, edible quality is poor. It is one of the most cultivated types in the world and in China, and is suitable for the manufacture of starch and alcohol or for fodder.
3. Semi-horse-tooth type: also called intermediate type. It is a cross between hard-grain and horse-toothed corn. The top of the kernel depression is shallower than the horse tooth type, and some are not depressed only white spots. The powdery endosperm at the top is less than that of horse-toothed type but more than that of hard-grained type, and the quality is better than that of horse-toothed type, which is cultivated more in China. Various corn (9)
4. Powdery type: also known as soft type. The endosperm is all powdery, and the kernel is milky white and lusterless. It can only be used as a raw material for starch, and is rarely cultivated in China.
5. Sweet type: also known as sweet corn. The endosperm is mostly horny, containing more sugar, containing starch is low, because of the evaporation of water at maturity so that the surface of the grain is wrinkled, was translucent. Mostly used as a vegetable, China's planting is not much.
6. Sweet powder type: the upper half of the seed for the horny endosperm, the lower half of the powder endosperm. Few cultivated in China.
7. Waxy type: also known as glutinous type. The endosperm of the seeds is all horny but opaque and waxy, and the endosperm is almost entirely composed of branched-chain starch. It is like glutinous rice, sticky, soft and palatable. It is only sporadically cultivated in China.
8. Popping type: smaller seeds, rice-shaped or pearl-shaped, endosperm is almost entirely horny, hard and transparent texture, the seed coat is mostly white or red. Especially suitable for processing popcorn and other puffed food. China has sporadic cultivation.
9. lemma type: the grain is wrapped by the longer lemma shell, the kernel is hard, difficult to threshing, is a primitive type, no cultivation value. 1. yellow corn: the seed coat is yellow, including slightly reddish yellow corn. The U.S. standard for yellow corn in other colors of corn content does not exceed 5.0%.
2. White corn: white seed coat, including slightly yellowish or pink corn. The U.S. standard will be light yellow expressed as light straw color, and the white corn in other colors of corn content does not exceed 2.0%.
3. Black Corn: Black corn is a special type of corn, whose kernel cuticle precipitates melanin in varying degrees, giving it a dark and shiny appearance.
4. Glutinous corn: corn rich in viscosity.
5. Miscellaneous corn: corn mixed with corn other than this category in the above three categories of corn more than 5.0%. China's national standard is defined as corn mixed with more than 5.0% of corn outside this category. The U.S. standard is expressed as the color neither meets the color requirements of yellow corn, nor meets the color requirements of white corn, and contains white top yellow corn. 1. Conventional corn: the most common and commonly grown corn.
2. Sweet corn, special corn: refers to various types of corn other than conventional corn. Traditional special corn has sweet corn, glutinous corn and popping corn, the newly developed special corn has high quality protein corn (high lysine corn), high oil corn and high straight chain starch corn. Because of special corn than ordinary corn has a higher technical content and greater economic value, foreign countries call them "high value corn".
3. Sweet corn: usually divided into ordinary sweet corn, enhanced sweet corn and super sweet corn. Sweet corn on the production technology and harvesting requirements are more stringent, and short shelf life of domestic breeding of various types of sweet corn can basically meet market demand.
4. Glutinous corn: its production technology is much simpler than that of sweet corn, and there are almost no special requirements compared with that of ordinary corn, and the harvesting period is more flexible, and the shelf life is also relatively long, and it does not require special storage and processing conditions. Glutinous corn in addition to fresh food, or starch processing industry is an important raw material. China's glutinous corn breeding and production development is very fast.
5. High oil corn: high oil content, especially in linoleic acid and oleic acid and other unsaturated fatty acids content of 80%, pictures of corn (20) has a lower serum cholesterol, soften the role of blood vessels.
6. High-quality protein corn (high-lysine corn): the yield is not less than ordinary corn, while the whole-seed lysine content is 80-100% higher than that of ordinary maize, and in some areas of China, a combination of high-yield and high-quality has been realized.
7. Purple corn: is a very rare corn varieties, because the grain shaped like a pearl, there is a "black pearl". Purple corn quality is excellent and special, but the stick is small, fewer grains, mu yield is only about 50 kilograms.
8. Other: including high-starch specialty corn, silage corn, edible corn hybrids, controversial Pioneer 335 genetically modified seeds.