Corn Cultivation and the Effects of Temperature

Corn is considered one of the most important foods and industrial crops in the world after wheat and rice. It belongs to the Grass family of plants, and its importance resides in its multiple uses. In the last four years, corn cultivation in Iraq has witnessed a remarkable expansion, especially in the northern region of the country. Despite few agricultural issues such as the incompleteness of the ear or the so-called failure of pollination, this crop remains key as it covers many uses such as;

1- The grains account for up to 40% of the concentrated diet of poultry and livestock

2- The use of maize plants as fodder and for making (silage) and the remains of plants after harvesting are used as fodder for cows and buffaloes…

3- Extraction of starch, oil, and dextrin from yellow corn kernels.

4- After harvest, the leaves, stems, and stalks of the crop can be used to make paper

Corn is cross-pollinated by wind-blown pollen from the male flowers or tassels at the top of the plant to the female flowers or silks about midway up the stalks. Each kernel develops from an individually pollinated silk. Kernels develop near the middle and base of the ear first with those at the tip developing last. When unfavorable conditions occur such as those mentioned above, those kernels pollinated first will take precedence over those pollinated last. This often results in the failure of the kernels near the tip to develop properly.

One anther produces about (2500) pollen grains, one ear produces about (15000) pollen grains, and one inflorescence produces about (20-30) million pollen grains, so there are (20000-30000) pollen grains for each female flower, so the lack of pollen grains It is rarely a determining factor in the production of maize, provided that it spreads at the time when the female flower is capable of receiving pollen grains, and pollen grains remain alive for approximately 24 hours. The stigmas and silk-textured pens in the feminine inflorescence, locally known as  the ear of the ovary , emerge from the top of the ovary, and each pen extends along the covers that cover it and is pushed upward through the growth of the interstitial meristem at its base. Pollination growth may continue for (10-15) days, and thus its length may reach (30-40) cm on top of the covers, and once fertilization is done, the activity of the meristem stops.

Pollination occurs in yellow corn by the transfer of pollen grains from the male inflorescence to the female flower (the stigma and the pen )  and pollination in corn is usually mixed and reaches (95%) or more, which is the transfer of pollen grains from the anther of the flower to another flower on another corn plant of the same Item or compatible with it.

It is the sum of the temperature above the base temperature in which the biological activity of the plant is zero. The degree of 40 F (4,4C) was considered the degree to which the biological activity is zero. Thus, it is possible to calculate the accumulated temperatures for a day, a month, or for any period of time as follows:

If the temperature of a day rate is 26º C , the heat accumulated then for that day is 26 – 4.4 equals 21.6 m and total temperatures for the rest of the days of more than 4 , 4 m represents the heat accumulated to separate the growth of that crop , for example . By knowing the accumulated temperature, it is possible to know the period of growth of different varieties of crops in that area. One of the disadvantages of this method is that it does not take into account the intensity and duration of the heat. Nevertheless, this method has found a good scope for its use.

Reaching a stage of growth in any crop, must receive a certain amount of heat, regardless of the period of time it takes to receive those heat units. The sum of the temperatures above the basic temperature at which the biological activity begins is the base on which this method depends, and the base temperature. It was calculated based on the results of experiments for different crops and found that it is  10C for yellow corn . The number of units for any day is by subtracting the average temperature of the crop from the temperature for that day and by adding these temperatures, we get the number of heat units for any period from planting to maturity for that crop. This method has found great importance in its use in harvesting crops for the following purposes:

• Distinguish the growing season for varieties of corn
• Knowing the best date for transplanting
• Predicting the maturity date.
• Organizing access-harvesting operations.
• Controlling the quality of the crop.

The high temperature during the flowering and pollination process leads to the burning of the top of the plants, including the male inflorescence, which causes the death of pollen grains, and then the decrease of pollination and fertilization, which affects the stacking and fullness of grains and the lack of yield and low productivity..

In addition, higher temperatures lead to an increase in the rate of breathing at night, and then an increase in the rate of demolition over construction, which leads to a shorter ear length and a decrease in the number of plants bearing two cobs, and then a decrease in yield, and increase in temperature , humidity and irrigation leads to an increase Infection with diseases and pests such as paralysis, root rot, aphids and spiders

There is also damage to high temperatures on corn at the beginning of life. These damages appear on plants in the form of temporary wilt that turns into permanent wilt in case of exposure to high heat for a long time, as the rate of photosynthesis decreases with increased respiration, and then demolition increases and construction decreases. Which leads to a shortage in the rate of vegetative growth, especially if there is a deficit of irrigation water and if the plants are exposed to thirst.

1- Losing part of it by washing, which does not allow the plant to get its need of this element
2- Withdrawing a part from the roots of plants, i.e. continuous depletion without compensation by   adding it to the soil or spraying plants, especially in areas where crops that deplete this element are grown intensively without following an agricultural cycle.
3- Increasing the soil content of calcium that hinders its absorption.
4- Ground water level rise

1. Irrigation during the afternoon or at night during the vaccination period to ensure that it does not stick and lose its vitality
2. Avoid thirst by prolonging irrigation periods, especially during flowering, so as not to affect the process of pollination and fertilization, and thus reduce the yield. .
3. Avoid flooding (increasing irrigation water) so as not to lead to yellowing of the leaves, and the size of the ear will decrease, and thus the crop will decrease.
4. Refrain from performing the two processes of securitization (removal of green leaves from plants) or tamping (removal of the upper part of plants) for feeding livestock
5. The securitization procedure leads to depriving the plants of the formation of dry matter and thus the yield decreases

Eng. Amjad Ibrahim