Spain: Mandarins and grapefruit can be grown with purified water

The fact that water is a scarce resource is shown in the amount of studies that researchers in the Region of Murcia are doing to find out the effects of using unconventional water resources for irrigation.

The doctoral thesis of Cristina Romero-Trigueros can be framed within this context. She has investigated the use of water from the wastewater treatment plant of northern Molina (which has a high salt content) in citrus crops, such as grapefruit and mandarin, looking into the possible physiological and agronomic repercussions.

For twelve years, the researcher has taken samples and monitored the results in the farms under study, and has found that mandarins irrigated with purified wastewater yield between 5 and 6% less production.

"However, the quality of the fruit has improved. It has higher Brix degrees (sweetness) and the calibers are the same, so we could say that using this type of water is worth it," says the researcher.

As for grapefruit, both the production volume and the caliber remain the same when the trees are irrigated with purified water, and the Brix degrees also improve. "Grapefruit has proven to be very resistant to the salinity of the waters," says Romero.

The young researcher has also studied the effect that the lack of irrigation has on both citrus fruits. The results are less positive.

In the case of mandarins, when irrigation water is reduced by 20 percent, the production volume falls by 18%. The caliber also shrinks "a little."

However, water stress causes the quality to improve, and a sweeter fruit is obtained.

Grapefruit is more resistant to water stress, and its impact is not especially noticeable in the caliber, although it does take a toll on the tree. As is also the case with mandarins, after two or three years, the leaves begin to yellow.

In all cases, the trees have received a normal amount of fertilizers.

The thesis of Cristina Romero-Trigueros has received the Extraordinary Doctorate Award from the International Doctoral School of the Polytechnic University of Cartagena.

Her work is part of the doctoral program Advanced Techniques in Research and Development on Agriculture and Food and has been carried out under the direction of doctors Emilio Nicolás Nicolás and Pedro Antonio Nortes Tortosa, researcher and head of the Irrigation Department of Cebas-Csic.


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