Why do corn plants heart the heat? Because they undergo adifferent kind of photosynthesisthan many other food crops. Most plants stop photosynthesizing efficiently above 90 degrees Fahrenheit, but corn actually grows more efficiently and productively at high temperatures.
Varieties Of Corn
Varieties of corn can be divided into three basic types. Each type has different uses. The varieties are distinguished by the molecular makeup of their kernels.
The most familiar to Americans is sweet corn. The kernels have high levels of sugar in their kernels and soft, chewable skins.
This is the variety that is eaten as corn on the cob or added into various dishes like corn chowder or succotash.
Popcorn and flint corn are the hardest varieties—they have thick outer skins and high levels of stored protein around a starchy core. This hard outer shell is what creates the internal pressure when heated that makes popcorn “pop”.
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Ask at your local farm store, extension agency, or farmers market to find out what varieties grow best in your area.
Planting And Growing Corn
As always, prepare your beds bytesting and amendingthe soil. Corn likes a soil pH between 5.5 and 7. If you have acidic soils, adding lime will help both your pH and your calcium levels to give you a more successful crop. Compacted soil can be amended by deep tillage and the incorporation of organic matter, but theessential soil texturecannot be changed.
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Corn is a grain crop, meaning it is typically direct-seeded into the field. Seed spacing for corn is 4-5 inches—if you are using a mechanical seeder, you will need a special plate for corn, since it’s seeded more widely than most other grain crops.
Direct seed corn after the last frost, when daytime temperatures are above 60 degrees Fahrenheit. It takes up to 100 days from seeding to maturity, so corn needs a long, warm growing season.
Sweet corn is harvested green, or immature, while the kernels are still full of water. Mature corn dries down on the stalk like wheat, the moisture evaporating from the kernels so that it can be stored.
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Corn can be grown in temperate, northern, or coastal climates. However, since there are not enough reliably hot days at the end of the growing season, these climates are not conducive to growing a dry-grain crop. Ears of corn are expected to fully mature and dry in the field before harvest, and without warm enough temperatures, they aren’t able to dry out.
In warm climates, corn is best planted in late April or early May, when the soil is warm and moist, giving plenty of time during hot weather for the crop to reach full maturity.
Corn is vigorous and leafy, so once it gets established, it should shade out weeds. In the first few weeks, after planting until shortly after germination, corn can be mechanically weeded using a tine harrow, in organic systems, or sprayed with pesticides for weed control.
Another trick for controlling weeds at germination: Plant at the beginning of a dry spell and wait several days to a week before watering.
Since corn kernels are large, they are not as easily parched by heat and dryness and will begin to germinate slowly even without water. Weed seeds, which are relatively small, will not. This gives the corn a head start on germinating to help them out-compete the weeds.
Corn is a hardy, warm-weather crop, but it needs regular water—about 1 acre-inch per week. This is especially important during the flowering phase as tassels develop. Drought at this stage will result in stunted or empty ears.
Troubleshooting Problems, Pests, And Diseases
Corn is susceptible to several pests and diseases. Always practice good crop rotation, which is the most effective control for all types of problems.
The most common pathogens infecting corn arefungi. These ailments include various blights, common rust, leaf spot, and stalk rot. Fungi thrive in damp conditions, so be careful not to over-water and always rotate your crops into an unrelated species like legumes.
与固氮作物轮作也能提高土壤肥力。If crop rotation is not working to control the fungus, use of anorganic fungicidemay be necessary.
Yellowing leaves can be a sign of nitrogen deficiency, especially if the crop was not properly fertilized before planting. This condition is distinct from leaf spot and blights in that the yellowing will be more uniform than spotty or mottled, and it should improve with the application of fertilizer.
Pests love corn, from tiny insects to critters like crows and raccoons. Since the kernels are full of sugar, it is an enticing meal for any animal or bug.
Birds are a big problem in grain production. They eat the seeds as they are planted before they even germinate. Be sure your seeder is adjusted to plant deeper than 1.5 inches, to prevent crows, geese and other birds from picking the corn kernels up like birdseed.
If you are just growing a garden, you can use mesh netting over your growing area. Scarecrows are a cute decoration but don’t really work. Some farmers use noise machines to discourage birds.
由于它的外皮保护玉米粒不受许多昆虫的侵害，玉米经常受到钻洞和无聊的害虫的困扰，比如各种蠕虫和蛆。蚜虫和甲虫攻击树叶和茎干。Here are some common corninsect pestswith potential remedies.
Harvesting, Processing, And Storage
To test whether corn is ready to harvest, peel back the husks on several ears to look at the corn inside.
If you are harvesting fresh sweet corn, you are looking for ears that are full and plump, with large, fully developed kernels. When you puncture the kernels they should let out a milky liquid. This is the “milk stage”—clear liquid means the crop isn’t quite ready.
Usually, this stage is about three weeks after the silks have developed, once the silks have turned brown but the husks are still green. Ears of corn are easy to harvest. Either cut off at the base of each ear against the stalk with a harvest knife or simply grasp the ear and yank down while twisting.
Field corn is harvested with a combine when the kernels are hard and dry. The combine, as its name suggests, is a machine that combines cutting and threshing—separating the grain from the stalk.
Corn History And Controversy
Native to the warm regions of the Americas, maize was a staple crop for indigenous civilizations from Peru all the way to the southeastern U.S. Once introduced to Europe it swiftly became a part of Mediterranean cuisine in dishes like polenta. Now corn is frequently vilified. Starchy and high in sugar, it can be processed into corn syrup, corn starch, corn flour, and animal feed.
早在一万年以前，人们就开始种植这种高大、高产的草。如今，它是世界上继小麦和水稻之后的第三种主要食用作物。It producestwice as many calories per acreas wheat.
Corn is one of the most versatile foods, used in recipes around the world in addition to being a ubiquitous additive. Sweet corn can be added to chowders, soups, stir fry, curries, salads, tacos, even pasta. Dry corn can be ground into coarse meal for cornbread or grits. And of course, no American fair or rodeo is complete without grilled corn on the cob.
How To Make Masa
Masa, which means dough, is made through a process callednixtamalization. Nixtamalization, derived from an Aztec word, is an ancient process through which corn is soaked in alkaline water, usually using lye or sodium carbonate from ashes or lime. Calcium is a very reactive molecule and the alkaline treatment has a chemical effect on the corn that changes not only the flavor but the nutritional content.
硝铵化软化了玉米细胞壁的一种重要分子成分半纤维素，它在碱性条件下是可溶的，使玉米的外壳松开。Additionally, the process releases boundniacin, a B vitamin which is essential for the body to process food into energy. Without nixtamalization, very little niacin is available in corn. The alkaline processing is also responsible for the distinctly nutty, savory flavor and aroma of corn tortillas and chips.
- 2 pounds dry corn
- ¼ cup food-grade lime (calcium hydroxide)
- 3 quarts water
- Put dry corn in a pot of water and bring to a boil. Add the lime.
- The corn is left to soak overnight, for 8-16 hours, which softens the outer skins.
- In the morning, rinse the corn, allowing the loose hulls to wash off. Drain the water.
- Fresh masa can be used immediately or it can be flash-dried.
Dried masa is called masa harina, and you can buy it at any grocery with a Hispanic foods aisle. Just add water, and it is ready to use.
Whether you are just starting out or if you are an experienced corn grower who is looking for new tips, always remember to ask other gardeners, local experts, farmers at the market, specialists at yourcounty extensionor members of your local master gardener program. When we are farming or gardening, the most important thing we are cultivating is community.
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