Orange Trees
The cultivation of citrus fruits in the Valley has been present since the 11th century, when it was introduced by the Arabs from the East, and its cultivation presents the originality of being associated with the olive tree to protect the orange trees from cold winds and winter frosts, what constitutes one of the main differentiating characteristics of its landscape nowadays.
The variety of orange grown in this area is the Navel or Navelina. The ripe Navelina orange has an intense orange color, large size, rounded and slightly oval shape. It is a little protruding, it does not contain seeds, the pulp is Fleshy and contains a large amount of very sweet juice, it is commonly used to be eaten, but also it can be used for making juice.
Factors that affect its quality
Genetic factors, factors related to the climate, the crop, as well as the state of maturity at the time of orange harvesting have a great impact on the quality of the orange. In the first place, we could highlight the following climatological factors:
- temperature,
- sunlight,
- relative humidity,
- frost and hail,
- the wind, and
- rainfall.
While the temperature can affect the texture and appearance of the orange, an orange production continuously exposed to high temperatures and excessive sunlight can cause external alterations in the orange such as color alterations. In the same way, an exposure to very low temperatures will also damage the harvest, causing its quality to decrease.
It is considered that for most fruits, the higher the temperature during the growth period, the faster their maturation will be, the acquisition of their flavor. In addition, the fact that there are temperature differences between day and night is important for the development of "color" in ripe fruits.
The greater or lesser exposure of the orange to sunlight will affect it, specifically in its appearance, in its coloration.
Regarding relative humidity, it is directly related to the “irrigation” factor since, as in all factors, you must have the right measure. The influence of this factor has been studied especially in citrus fruits and it is considered that at high relative humidity the orange peel is thinner and has a greater amount of juice than in cases of low relative humidity in which it has been proven that the skin is thicker and the orange and less amount of juice.
Needless to say that hail and frost damage both the production of the orange and its quality, directly affecting the external appearance of the oranges. It is a climatic factor that damages the orange in any state of maturity.
The wind as a climatic factor has a great influence on the final quality of the orange as well as on its "useful life". We are all aware that the movement produced by the wind in the branches of orange trees can cause rubbing or scratching both of the oranges among themselves and between them and the branches. This causes changes in the appearance of the oranges (marks or "wounds" on their skin) which reduces their quality and probably shortens their shelf life.
Finally we have rainfall, another climatological factor to take into account given that its quantity and distribution over time will affect the quality of the orange.
Although in the rest of Spain the collection of this variety goes from October to the end of January, in El Valle they begin to be good at the end of January and last until April, so we are going to focus on the influence of rainfall, frosts suffered in December and January (below -3ºC) and temperature variation.
To carry out the study, data on production in kg / ha have been obtained from the agricultural and fisheries statistics yearbooks of Andalusia, from 2005 to 2018, which are those that appear on the website of the Junta de Andalucía.
Production Statistics
We can observe that the average production has been about 18,000 kg / ha and the trend has decreased over the years. From 2010 to 2013, the production was significantly lower, and we will try to check if the climatic data have affected this decrease.
Relation between Production and Climate Factors
If we make a scatter diagram between the two variables and calculate the regression line with Excel, we obtain the following equation, where we observe that the regression coefficient is quite low, so we cannot affirm that there is a linear relationship between them.
and its correlation coefficient is r= -0,392.
Prediction for 2019
According to the results, it also seems that the more it rains, the more the production decreases, which is not very logical.
Even so, we will try to make a prediction of the production with the rains of 2019 that are 339.2, obtaining:
Production = -18.338x339.2 + 25913.6828 = 19639.43 kg / ha (above average).
We have taken into account frosts only in December, because the farmers in the area told us that they were the ones that affected production, but as the rains, if we calculate the regression line between both variables, the program tells us that this relationship is practically nil.
and the correlation coefficient is r=-0.05.
Prediction for 2019
Production = -155.27 x 0 + 18289.39 = 18289.39 kg / ha (above the average)
If we take into account all the frosts registered during the winter of each year, if it is blatant that the greater the number of frosts, the worse the harvest is, although in this case the prediction obtained with the regression line is not good either.
The green line that we have drawn is the linear relationship that we could intuit, although it is not the one that the program gives us (orange color).
Finally, if we study the variation in temperature that there is every day and the production, we realize from the data obtained that when calculating the average variation of the year, the data are very similar and cannot explain a change in production, even so we calculate the scatter diagram of both variables and their associated regression line.
Correlation coefficient r=0.1334.
Prediction for 2019
Production 1,451.2494x13.65-1,090.9936 = 18,718.56 kg / ha (above average).
Summarizing,
A remarkable fact, which farmers have told us, is that more and more people are choosing to plant avocado instead of orange, although this crop is more fragile, the profitability it brings them is much higher.
As the location of the orange tree is in the villages of the valley and not in Dúrcal, we have tried to find data from another meteorological station, just in case if the problem laid there.
We do not know the exact location of this station, we have obtained data from http://www.adurcal.com/enlaces/cultura/patrimonio/clima/index.htm
Although data corresponding to 2012 and 2013 are missing for several months, which was the reason why we refused to use them. at the beginning, finally we have tried to get to some conclussions.
and the correlation coefficient is r=0.052.
The relationship is worse than before, but in this case it is positive, that is, the higher the rainfall, the higher the production, but the linear correlation coefficient is practically zero.
and the correlation coefficient is r=-0.328.
It is better than the previous result, although we have taken into account all the frosts of the year, not only those of December as in the previous case, which were the ones that the farmers told us that most affected the orange trees.
We can see that in 2012 when production fell a lot, a total of 11 frosts occurred.
and the correlation coefficient is r= 0.131.
The data obtained are very similar to the previous ones, in both cases the coefficient is practically the same.
Summarizing,
Recall that the average production was 18,067.57 kg / Ha