1. INTRODUCTION

Corn is a very remote farming about 7000 years old, of Indian origin was grown in the areas of Mexico and Central America. Today our culture is very blurred for all other countries, particularly in Europe where it occupies a very high position. U.S. is another country that stands out for its high concentration in the maize crop.
Its origin is unclear but is considered to belong to a culture of Mexico area, because their findings were the oldest there.

2. Morphological characteristics. BOTANY

Common name: Corn

Scientific name: Zea mays

Family: Gramineae

Genus: Zea

BOTANY

The corn plant size is robust and easy development of annual production.

Stem

The stem is erect simple, high length and can reach 4 meters high, is rugged and ramifications. By the look reminiscent of a reed internodes and if no one if done spongy bone cross section.

Inflorescence
Maize inflorescence is monoecious with separate male and female inflorescence within the same plant.
As for the male inflorescence has a panicle (commonly called spike or plume) of yellow that has a very high amount of pollen in the order of 20 to 25 million pollen grains. In every flower that makes up the panicle are three stamens where pollen is developed. In contrast, the female inflorescence marks a lower content of pollen grains, around 800 or 1000 grains and are formed in vegetative structures called spathes which are arranged laterally.

Sheets
The leaves are long, large, lanceolate, alternate, parallel veins. They are embracing the stem and the beam has villi. The ends of the leaves are very sharp and cutting.

Roots
The roots are fasciculate and its mission is to provide a perfect anchorage for the plant. In some cases protrude knot of roots at ground level and usually occur in those secondary or adventitious roots.

3. MAIZE VEGETATIVE DEVELOPMENT

Since seeds are sown until the appearance of the first outbreak after a time of 8 to 10 days, which is very reflected the continued rapid growth of the seedling.

4. GENETICS OF CORN

The corn crop has taken a very studied for scientific research in genetic studies. Continually studying genotype and for being a monoecious plant that provides great information and has a maternal side (female) and one paternal (male) so you can create multiple recombinations (crosses) and create new hybrids to market.

The objectives of this crossing are aimed at obtaining high yields in production. Therefore, mass is selected plants that are more resistant to viruses, weather, pests and develop a good size to cross with other maize plants which provide certain characteristics of what you want to achieve and improve crop. Also selected according to the shape of the ear of corn, especially those that have a high grain content without distortion.

5. Edaphoclimatic SITUATION

5.1. Requirement of climate

Corn requires a temperature of 25 to 30 ° C. Requires considerable incidence of sunlight and on those humid climates is lower performance. To produce the seed germination temperature should be between 15 to 20 ° C
The corn comes to stand temperatures as low as 8 º C and from 30 ° C may appear serious problems due to malabsorption of nutrients, minerals and water. Required for fruiting temperatures of 20 to 32 ° C.

5.1.1. Rainfall and irrigation

Pluviometry
The water in rain are much needed in periods of growth in a content of 40 to 65 cm.

Irrigation

Corn is a water-demanding crop in the order of about 5 mm per day.
The risks can be made by spraying and blanket. Watering is the most widely used lately sprinkler irrigation.

Water needs will vary throughout the growing and when the plants begin to birth requires less water but maintain a constant humidity. In the vegetative growth phase when more water is required and it is recommended that a risk about 10 to 15 days before flowering.
During the flowering stage is the most critical because it will depend on the setting and the amount of production obtained by what risks are advised to keep moisture and allow for effective pollination and fruit set.
Finally, for the thickening and maturation of the ear should decrease the amount of water applied.

5.2. Soil requirements

Maize is well suited to all types of soil, but soils with pH between 6 and 7 are the best suited. They also require deep soils rich in organic matter with good drainage flow to produce no puddle that root cause suffocation.

6. CULTURARES WORK

6.1. Preparing the ground.

Land preparation is the step prior to planting. It is recommended that a plowing the field with the ground grade to hang loose and be able to have some ability to raise water without ponding. It is intended that the land especially the fluffy surface layer where planting will occur.
Also done work with moldboard plow to a depth of work 30 to 40 cm.
In the land tillage operations should be clean of plant debris (stubble).

6.2. Siembra.

Before performing the selected planting those seeds resistant to diseases, viruses and pests.
Planting is done when the soil temperature reaches a value of 12 ° C. It is sown at a depth of 5cm. Planting can be done to death, on the flat or grooves. The separation of the lines of 0.8 to 1 m and the separation between beats 20 to 25 cm. Planting is done by April.

6.3. Fertilization.

Corn needs for its development a certain amount of mineral elements. Gaps in the plant are manifested when a mineral nutrient deficiency or excess is.
We recommend a subscriber rich soil P and K. In quantities of 0.3 kg of P at 100 kg of fertilizer. Also a contribution of nitrogen N in greater numbers especially during vegetative growth.
The subscriber is typically carried out according to the characteristics of the planting area so that a subscriber does not follow rigorous in all areas equally. But a subscriber applies very weak in the early days of development of the plant until the plant has a number of sheets of 6 to 8.
From this amount of leaf subscriber is recommended:

N: 82% (nitrogen fertilization).
P2O5: 70% (phosphorus fertilizers).
K2O: 92% (paid in potash)

During the formation of grain from the cob subscribers should be minimal.
It should make for a subscriber maize background 825Kg/ha amounts during cultivation.
The dressing of are those made when the first leaves of the plant and most widely used are:

Calcium ammonium nitrate. 500 kg / ha
Urea. 295kg/ha
Nitrogen solution. 525kg/ha.

It is important to a subscriber adjusting to the needs presented by the plant in a controlled and intelligent.

Nitrogen (N): The amount of nitrogen to apply depends on the needs of production that want to achieve and the type of soil texture. The amount applied is from 20 to 30 kg N per ha.
A shortage of N can affect crop quality. Symptoms are most reflected in those photosynthetic organs, leaves, yellow colors that appear on the tips and are spreading throughout the entire nerve. The ears are no grains on the ends.

Phosphorus (P): Your dose also depends on the type of soil present either red, yellow or black soils. The match gives strength to the roots.
Its deficit affects fertilization and grain will not grow well.

Potassium (K) should be applied in an amount greater than 80-100 ppm in case of sandy soils and clay soils are higher doses of 135-160 ppm. Potassium deficiency makes the plant very sensitive to fungal attacks and his bearing is weak, because the root is severely affected. The ears not much on the tips.

Other elements: boron (B), magnesium (Mg), sulfur (S), Molybdenum (Mo) and zinc (Zn). They are nutrients that may appear poorly to or in excess in the plant.
Boron deficiencies are very marked in the ears with no grain in some parts of it.

6.4. Herbicides

When within 3 to 4 weeks of the emergence of the first herbal plant appear spontaneously to compete with the crop uptake of water and nutrients. Therefore, it is convenient removal by herbicides.
For the realization of ridging, weeding and desuckering chemical controls have been carried out with herbicides. The herbicides used are:

Triazines
It is the most widely used herbicide in corn. Your application may be made before planting or when there is the birth of the seedling and in the early post. Your dose will give 1 to 2 kg / ha. In sandy soils with herbicide treatments can damage crops are especially sensitive to this culture.

Simazine
Its use is in conjunction with triazine and serves to combat Panicum and Digitaria.
The dose of 0.75 and 1.25 kg atrazine / ha of simazine.

Dicamba
This herbicide is from the chemical formula of 2.4-D, and is not advisable to use in sandy soils. It is effective against Polygonum spp. and Cirsium arvense.

Cloroacetaminas
These herbicides act alone or mixed with atrazine. Eliminate weeds such as Cyperus esculentus.

Paraquat
It is used before planting

Thiocarbamates
Herbicides are to be incorporated before planting because it is very volatile compounds. EPTC and butylate are

Metolachlor
Applied before planting or after the occurrence and control of grasses in the crop. Their dosage range varying from 2 to 3 kg / ha.

In most cases grass and dicotyledons appear together in the cornfields. Is desirable to eliminate the association of these herbicides:

- Atrazine / simazine.
- Atrazine / cinazina.
- ETPC / butylate.
- Atrazine + alocloro.
- Atrazine + metolachlor.
- Atrazine + penoxamila.
- Copper oxychloride Cumaína + with little effect.

6.5. Thinning

Culture is a task that is performed when the plant has reached a size close to 25 to 30 cm and is letting go one level per hit and they are eliminated remaining lar
Other cultivation are the hardened crust breaking ground for the adventitious roots (surface) to develop.

7. COLLECTION

To collect the corn cobs is advised that no moisture in them, rather dry. The collection is produced by machine to obtain a harvest clean, free and easy grain losses.
To gather the cobs are used harvesters trailer or tank combines with built-in and rip the ear stem, previously dried with hot air passing through the threshing mechanism and once again extracted the grains to dry to remove remaining moisture.

The harvesters have a head where the ears are collected and a threshing device which separates the grain from the cob, are also a cleaning devices, regulatory mechanisms of control of machinery and a tank or reservoir where grain is clean corn.
Other combines larger and more modern collectors have rollers that are crushing the stems of the plant. They work on large working width from 5 to 8 rows cob and also crushed a two-device screens clean harvest.

8. CONSERVATION

For corn grain conservation requires a moisture content of 35 to 45%.

For grain maize for the cattle it must have a certain moisture content and stored in containers previously cooling and drying the grain.

For sweet corn storage conditions are 0 ° C and a relative humidity of 85 to 90%. To the ears of fresh leaves are removed the wrap and packaged in trays covered with a thin plastic film.

Corn for grain is preserved as follows: must go through a drying process using a continuous flow dryer or drying box. These dryers warm, dry and cool the grain evenly.

9. PESTS AND DISEASES

9.1 Pests

Insects

- Wire Worm. They live in soil, sandy soils are rich in organic matter. These worms are beetles. Females do put 100 to 250 eggs whitish and spherical shape. There are gender and Melanotus Conoderus.
The larvae of wireworms are gold and are doing damage by feeding on all parts and underground plant seedlings. Cause serious deterioration in the plant and even death.
For their fight soil treatments are recommended as Parathion and others.

- Worms gray. Lepidoptera class are larvae of the genus Agrotis. Agrotis ipsilon. The larvae are of different colors black, gray and green color through gray and are cylindrical in shape.
The damages that arise are neck at the plant to produce serious injuries.
Control similar to control wireworms.

- Aphids. The most damaging aphid Rhopalosiphum padi is corn, because it feeds on the sap causing a decrease in final yield of the crop and aphid Rhopalosiphum maidis Corn is transmitting a virus to remove the sap from plants mainly attacking sweet corn, this last species also causes serious damage due to the rapid growth of corn.
The review is conducted by AFIC, whose active ingredients, dosage and product presentation are shown below:

- The European corn borer. Ostrinia nubilalis. This is a stem borer and develops 2 to 3 generations reaching their full larval development reaching 2 cm in length. The larvae begin feeding on corn leaves and introduced just inside the stem. Just breaking the stems and ears that have been damaged as well.

-Corn borer. These are two very damaging pest in the cultivation of corn:

Sesamia nonagrioides. This is a drill Lepidoptera whose caterpillars corn stalks producing extensive damage. The caterpillar is about 4 cm, winters in the interior of the corn stalks where they form pupae. Butterflies appear in spring depositing eggs on the leaf sheaths.
Pyrausta nubilalis. The caterpillars of the Lepidoptera is about 2 cm in length, which damage occurs by eating leaves and cornstalks dig. Egg-laying takes place in different parts of the plant.

As a method of fighting early planting is recommended for this pest will not develop, and the use of insecticides. Below are the active ingredient, application rate and product presentation:

- Corn spider mites, Oligonychus pratensis, Tetranychus urticae and Tetranychus cinnabarinus. His control is done through the use of phosphorus and Dimethoate Disulfoton.

9.2. Diseases.

- Bacterioses: Xhanthomonas stewartii attacks the sweet corn. Symptoms appear on leaves range from light green to pale yellow. In stems of young plants are one aspect of stain causing large deformation in the center and fading. If the disease escalates it can produce a low growth of the plant.

- Pseudomonas alboprecipitans. It manifests itself as spots on the leaves of white with reddish causing stem rot.

- Helminthosporium turcicum. It affects the lower leaves of corn. The spots are large 3 to 15 cm and the leaf is turning from green to brown. His attacks are more intense at temperatures from 18 to 25 ° C. The leaves fall if the attack is very marked.

- Antranocsis
It is caused by Colletotrichum graminocolum. They are reddish-brown spots and are located in the leaves, cause wrinkling of the lamina and leaf destruction.
As a method of struggle is the use of the technique of crop rotation and planting resistant varieties.

- Roya. The fungus Puccinia sorghi produces. They are brown pustules that appear on the underside and upper surfaces of leaves, they come to break the epidermis and contain successful with organs called teliospores.

- Coal corn. Ustilago maydis. They are galls on corn leaves, cobs and stalks. The disease develops at a temperature of 25 to 33 ° C
Their fight is done based on specific treatments with fungicides.

10. Forage maize

Forage corn is grown for livestock feed. Is collected and ensiled for supply in times of no grazing. The sowing is done on a massive scale if used as food in green so that the seed planting density of 30 to 35 kg per hectare is planted in rows spaced from one another from 70 to 80 cm and planting trickle. They choose varieties with high precocity for better plant growth.

Silage is a technique in which the corn or other feed stored in a place or building (silo) to anaerobic fermentation to occur. In short try grain stores and warehouses. There are several types of silos:

1. Field Silos
2. Silos on deposit.
3. Plastic bins
4. Tower Silos.

The nutritive value noted for its energy value in both protein and minerals content of corn silage dry matter is achieved with a well-preserved forage.

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