Rice cultivation . Poor in nitrogenous substances, for which reason it cannot be considered a complete food. In its average composition, 8% of nitrogenous substances can be considered. It has little more than 1% fat.
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- 1 Origin
- 1 General characteristics
- 2 Demands of cultivation
- 3 Subscriber
- 4 Site preparation
- 5 Sowing
- 6 Cultural tasks
- 7 Collection
- 8 Pests and diseases
- 9 Diseases
- 10 Preventive measures
- 2 Sources
Some historians claim that this cereal is native to Southeast Asia and has been cultivated for more than 7,000 years. There is evidence of its cultivation, prior to the year 5000 BC in eastern China , and before 6000 BC in a cave in northern Thailand .
Chinese literature considers rice as the basic food of that people since 3000 BC; which it states that planting of this cereal was the occasion of a ceremony and said that the rice was domesticated between 1,000 and 1,300 years BC Historians say that is from Asia , where it begins to spread rice towards India , during the invasion of the Aryans. They base their judgment that the Greek term oryza appears to be derived from the Sanskrit names yrini and arunya. However, the Bible does not mention the cereal in their accounts, therefore it follows that it was unknown in the Middle East, at the time that others described it in their testimonies.
The roots are thin, fibrous, fasciculate. The stem is erect, cylindrical, gnarled, glabrous, 60-120 cm. Leaves alternate envainadoras, linear, acute, long, flat limb. At the meeting point of the sheath and the limbus is a membranous, forked ligule, standing upright, presenting on the lower edge a series of long and silky cirrus clouds. Whitish green flowers arranged in spikelets whose set constitutes a large, terminal, narrow, hanging panicle after flowering.
Each spikelet is uniflora and is provided with a glume with two small, somewhat concave, keeled and smooth leaflets; the glumilla also has two shelled leaflets. The fruit is in caryopsis.
Rice flour, due to its richness in starches, is used to make various food materials, and it is also used, in some cases, in breweries in order to achieve sufficient alcoholic wealth while spending little malt.
The rice needs to germinate at least 10 at 13 ° C, considered optimal as 30 and 35 ° C. Above 40 º C germination does not occur. The growth of the stem, leaves and roots has a minimum of 7ºC, considering its optimum at 23ºC. With temperatures higher than this, plants grow faster, but the tissues become too soft, being more susceptible to disease attacks.
The ear is influenced by temperature and by the decrease in the length of the days. The panicle, usually called the spike by the farmer, begins to form about thirty days before the ear, and seven days after starting its formation it reaches about 2 mm. From 15 days before bolting, the bolt develops rapidly, and this is the period most sensitive to adverse environmental conditions.
Flowering takes place the same day as the ear, or the next day during the last hours of the morning. The flowers open their gummies for an hour or two if the weather is sunny and temperatures are high. A rainy weather and with low temperatures harms pollination. The minimum temperature for flowering is considered 15ºC. The optimum of 30 ºC. Above 50 ºC no flowering occurs.
The respiration reaches its maximum intensity when the ear is in a bag, decreasing after the ear. The high temperatures at night intensify the respiration of the plant, with which the consumption of the reserves accumulated during the day by the chlorophyll function is greater. For this reason, low temperatures during the night favor the maturation of the grains. Perspiration depends on humidity and ambient temperature and, like respiration, it also reaches its maximum at the moment when the ear is in a bag to decrease after the ear.
The average nutrient needs / mt of rice production are 21 kg of nitrogen, 11 kg of P2O5 and 18 kg of K2O. From these data we can deduce that a subscriber, thinking of a production of 7,000 kg, may be of the order of:
- 150 Units of N
- 100 pcs of P2O5
- 100 Units of K2O
In the Guadalquivir rice fields, 750 kg / ha of ammonium sulfate, 500 kg / ha of 18% superphosphate and 150 kg / ha of potassium sulfate are used. It is very common for growers to dispense with potassium. Others who have always subscribed with superphosphate limit their use to once every two years, and there is no shortage of those who always use nitrogen.
Potassium should always be used in the form of potassium sulfate instead of chloride.
- Foliar fertilizers (NPK) are often added to herbicides, to counteract the depression that they can produce in the rice plant.
- Copper sulfate is used to prevent the invasion of algae. The common thing is to apply it by putting copper sulfate stones in the spouts.
- Urea is used as much today as ammonium sulfate . Anhydrous ammonia is sometimes used.
When the rice turns yellow due to lack of N, a distribution of nitrate should be made at a rate of 150 kg / ha. However, this is not often done.
To do this, the water inlet on the plot is closed and, after a certain degree of draining, the outlet is also closed and, with no current, nitrate is applied, which is absorbed by the plants in 24 hours. Liquid fertilizers in suspension are increasingly being used. Apart from the comfort of use, it seems that there is a greater and better absorption of N at the beginning, which gives a more vigorous nascence and a few days advance in the culture.
The highest absorption of nitrogen and potash coincides with the period of maximum tillering. The one of phosphorus, magnesium and calcium, with the final phase of tillering. Most of the fertilizers are absorbed by the roots before fruiting begins. The absorption of mineral elements is greater the greater the development of the roots, which is favored by the oxygenation of the soil and by the circulation of irrigation water.
The terrain must be leveled very well, with slopes that must not exceed one per thousand, and it is even preferable to level to zero, which allows making tables of up to 15 ha. At the end of winter the lifting work is done with the moldboard plow or with a hook cultivator. In order to leave the terrain sufficiently disaggregated it may be necessary to take two double crossed passes of the scarifier. According to some farmers, it is not advisable to do the mudding work, because in direct sowing it seems that the nascence is difficult, although it is becoming more practical, in most cases, to give a slight muffling pass.
This pass is done with a tractor equipped with cage wheels, without overlapping between the passes, as was done previously.
Seeding can be done by broadcast, by hand, by machine or by plane. Planting should be done when the water is clear and the sludge has settled to the bottom. The amount of seed used should give rise to a certain number of stems / m2, after the tillering, which is the optimum productive for each variety, and which produce ears that ripen as uniformly as possible. For the short to dense panicle varieties and rather thick stem, the most convenient number of stems / m2 can be estimated at 250-300, while in long open panicle varieties, with fine stem, this number must be between 300-350 stems / m2.
In any case, it is always advisable to increase the seed dose somewhat, especially in early sowings and with varieties with great budding. The average sowing dose would be 140-180 kg of seed per ha.
The sowing should be done with the ground flooded with about 5 cm high. Immediately after planting, without the rice being born, the water level is usually increased to 10 or 15 cm, which damages the development of the Panicum. This level rise goes badly for rice, because at birth it is fined, and even whole plots can be lost.
When sowing the rice, the rice does not cover anything. The machines have tubes that can go above the water level. When sowing is done by plane, it should not fly too high, since in this case the seed penetrates too much and it is not born. The plane should plant when there is no wind.
Once the crop is implanted, the tasks to be carried out are related to irrigation and the application of herbicides and pesticides where appropriate. In irrigation, care must be taken that the water level is at the proper height in relation to the development of the plant. In the first days, the level must be high, to protect the seedling from the cold, hinder the development of weeds, prevent the surface movement of water by the wind from plucking the young seedlings, not yet rooted, and if certain herbicides are used, preventing their degradation.
As the plant grows, it is convenient to lower these levels to allow better development and respiration of the leaves , which must “tap” above the water. The purposes pursued with the dry are to control the vegetative development when it is necessary, avoiding risks of bedding, and to prepare the plant for the fruiting period, as well as being a way of defending against the numerous algae that are raised under the protection of the plant. rice, which hinder the circulation of water and come to bother the plant. The dry is usually used for the application of contact herbicides, which require wetting the plant, since at the same time the dry causes an outbreak of weeds that were slowed down by the sheet of water.
The percentage of whole grains over the total of the harvested is very important in the price of rice, this being an important value when choosing a variety, but it is also decisive at the time of harvesting, and it is because if it is Mowing very green rice has to be handled a lot in the dryer, with the result of a decrease in said percentage. After harvesting, the stubble is normally burned and the “tangueo” work is carried out, which consists of moving the mud with special wheels. Harvesting is done with a combine equipped with tracks.
When the rice begins to grain, the irrigation is suspended. The maturity of the rice is proven by the hardness of the grain to the tooth, which must offer sufficient resistance to prevent cutting it. After threshing, rice can have a humidity of 25 to 30%, so it must be dried until it reaches a humidity level of less than 14%. Drying can be done in the sun or through thermal dryers.
Plagues and diseases
- Borer on rice (Chilo suppressalis): this Lepidoptera larvae are what really make the damage introduced into the stem of the rice and forming galleries. There are indirect means of control that are very useful such as lifting the plants after harvesting and stacking and burning them. Another indirect measure is to flood the plots during winter. Treatments can be done with various products such as Fenitrothión or Piridafentión.
- Pudenta (Eusarcoris sp.): It is an insect of the order of the Hemiptera, family of the Pentatomids, which is known by the names of paulilla and stink bug. Chop the grain producing spots that have been baptized by some industrialists with the name of “partridge’s eye”.
The main damages are not due to the decrease in the harvest, but to the deterioration of the grain quality. Among the active materials used, Malathion, Carbaryl and Trichlorfon stand out.
- Rice weevil (Sitophilus oryzae): It attacks mainly the barn, and not only feeds on the grains of rice but on any other cereal. The commercial products that are applied in the treatments are based on aluminum phosphide or magnesium phosphide. Aluminum phosphide is extremely toxic by inhalation, so the rooms where it is applied must have a good ventilation system.
- Black donut (Spodoptera litoralis): The black donut, Lepidopteran, which is now known by Spodoptera litoralis and formerly Prodenia litura or litoralis, also attacks rice sometimes. More than black they are greyish or greyish brown. They do great damage by devouring the leaves. Larvae must be fought when they are small, because when they are large they are very resistant. They are killed with sprays based on carbaryl, fenitrothion, trichlorfon and others.
- Worm of the rice seedlings: They are diptera and there are three different genera: Chironomus, Ephydra and Ortocladius.
- Control means: A dry one occurs and, when the water is removed , the plants are pulverized, making the water enter half an hour later, closing the nozzles and keeping the level constant. Carbaryl, Malathion, etc. can be used to spray.
- Aphids: Although not very frequent, aphid invasions sometimes occur in rice. To fight against them there are numerous aphidicides such as etiofencarb, malathion or fenitrothion.
Among the diseases that rice fields suffer, the most fearsome is Pericularia oryzae, caused by a microscopic fungus. The mycelium of the fungus produces a toxic substance known as pericularin, which inhibits the growth of tissues and disorganizes them.
- Control methods: Bordeaux broth is used, at a rate of 1,200 l / ha (0.4% copper sulfate), but the treatment, which must be repeated to be effective, is very expensive and produces losses in the harvest yield.
- Use of varieties that are not very sensitive to the attack of the fungus.
- Do not abuse the nitrogen fertilizer.
- Use a balanced fertilizer with phosphorus and potassium.
- Late withdrawal of water in the maturation period.