Peanuts (Arachis hypogaea) are native to South America (Bolivia and neighboring countries) and are now cultivated in all tropical regions - overcast in the world. This cultivation was widely carried out by native peoples (Maya, Aztecs and Toltecs) until the time of European expansion in the 16th century and then, subsequently taken to Europe, Africa, Asia and the Pacific islands. Peanut was first cultivated in gardens in the United States until 1870 to be given to pigs, then later around 1930 it was decided to allocate it to man as an edible product. All parts of the plant today can be used. Peanut grown mainly for human consumption has several uses; whole seeds are eaten as appetizers or turned into butter, fried oil and other products. The seed contains 25-30% protein (on average 25% digestible protein) and 42-52% oil. One kilogram of peanuts is high in food and provides the same energy value as one kilogram of beef, one kilo and a half of cheese, nine liters of milk or thirty-six medium-sized eggs. Peanuts are consumed mainly as roasted seeds or as butter in a particular way in the United States while, in the rest of the world, production is translated into edible oil and in some cases as fuel for processing artifacts and agricultural machinery.
The peanut is born with the system of self-pollination for an indefinite period and is an annual herbaceous legume. Natural pollination occurs quickly due to atypical flowers or bee action. The fruit is a pod that contains from one to five seeds that develop inside a structure called "nail" that has an elongated ovarian shape. The leaves of the peanut plant are alternate and pinnate with four leaflets (two pairs per leaf). The peanut plant can be erect or prostrate (from twelve centimeters in height) with a well developed taproot and many lateral roots and nodules. During early growth, the plants develop three main stems, that is, two stems ranging from cotyledonary axillary buds of equal size to the central one. There are also bright yellow flowers with male and female parts that are found on inflorescences similar to spikes in the axils of the leaves. One or more flowers may be present in each node and are usually more abundant in the lower parts of them. The first flowers appear four to six weeks after sowing, and the production is obtained after a maximum of twelve weeks. After fifteen days the pods are formed which can reach maximum dimensions in two or three weeks. The peanut harvest matures in about two months and is indicated to us by the maximum levels of protein, oil, dry substance and the presence of dark veins and the beige colored shell. The characteristic of this plant is that it has a continuous flowering for a long period from the moment of development until the time of harvest.
Temperature is the main element that allows a good yield of peanuts. In cold countries the cultivation is therefore limited because, the ideal temperature to obtain a good product must be at least twenty-eight or thirty degrees. Light is therefore essential along with good soil drainage and organic substances that are ideal for peanut development. The preferred soil is usually loose and brittle allowing easier penetration of the roots and pickets, and a better defense against rain and therefore favorable to a good harvest. Light colored this soil allows a good drainage and provides proper aeration to the roots and to the proliferation of nitrifying bacteria that are necessary for the correct mineral nutrition of the plant. Fertilizers must however be administered in the first stage of plowing the soil so that slits can be made in which to insert the precious liquid, which reduces the loss of stem cells and the risk of disease.
Peanut plantations respond well to soil fertility, but are usually reluctant to fertilizers with too high fertility levels. However, when nutrients are necessary, it is essential to use those based on potassium chloride. Another important maintenance is the periodic verification of the degree of soil acidity and the optimal PH level must fluctuate from 6.0-6.5. Another essential nutrient is calcium, which together with nitrogen are among the main chemical products that the plant requires for its development. Finally we take care of the watering. These must be abundant otherwise the plant is likely to absorb in the absence of it, excessive liquid and solid substances present in the soil impoverishing it with serious risks for its own health. Watering should be done at sunset and early in the morning. For large-scale cultivation, watering occurs through irrigations controlled by continuous-cycle pumps, which distribute water constantly and above all in a nebulized form, avoiding the creation of stagnations that could cause the plant to rot.
As mentioned above, one of the fundamental aspects to obtain good fruits with the cultivation of these plants is related to the climate; in areas with low temperatures, this crop is not recommended, unless special greenhouses are installed that can maintain the right temperature. For their growth, these tree species require a minimum temperature of 15 ° C for what concerns the germination phase, but they need temperatures above 20 ° C in order to grow and develop sufficiently, providing a good product to consume. The soil must be draining and soft, this is because the fruits develop underground and need to be able to expand easily. The soil can be prepared with special handling tasks, performing them in the winter period, so that in spring it is ready to accept plants of this type. To plant this type of crop, proceed with sowing, using however non-toasted fruits that still have the classic red film and placing them in special holes with a minimum depth, around 3 cm. It is important to proceed with regular watering but not allowing the formation of water stagnation, a factor that can easily lead to the formation of mold.
The harvest of these fruits must be done when you see the plants turn yellow; the plant must be extracted leaving earth on the roots that are the ones that bear the fruit. The plants are then left to dry to ensure that the earth comes off to remove the pods containing the peanuts, which will be placed in a cool, dry place to let them ripen and dry.