Where do olives grow in India

Success with downsides

It is fair to say that olive oil is conquering the world. This can already be seen in the expansion of the olive tree plantations. The plant physiologist and olive specialist Arnon Dag from the State Agricultural Research Organization of Israel in the Negev desert:

"Today there are 30 million hectares of olive plantations worldwide. The production volume has roughly tripled in the last two decades - because the demand for olive oil has increased enormously. Originally, olive trees were only grown in the Mediterranean region. Now this is also happening in South Africa, in the USA, South America, Australia - and even China and India. "

However, this expansion has disadvantages. Almost all olive tree plantations are now artificially irrigated in order to achieve high yields. As a rule of thumb, you need 120 times the amount of water to produce one liter of olive oil. And that in cultivation regions that typically have a Mediterranean climate and where fresh water is therefore scarce. Arnon Dag is one of those researchers who are looking for a way out of this dilemma. At the biohydrology conference in Landau in the Palatinate, he now reports on possible solutions in Israel:

"Fortunately, olives are quite insensitive to salt. That is why we can use treated wastewater for their irrigation. In Israel this is the case on half of the cultivated area. We are one of the leading countries on earth. We also pump salt water from reservoirs in the subsoil, for which there is no other use, and also use it to water the olive groves. In this way, we do not use fresh water. "

According to the botanist from the Negev desert, this method is now also used more frequently in Italy and North Africa. It even saves fertilizer. Because treated wastewater still contains important plant nutrients such as phosphorus and potassium. On the other hand, one wonders: Are the soils not too saline through the use of wastewater? But Arnon Dag and other experts have also found a solution for this:

"It is necessary to wash the salt out of the root zone. That is why we water a little more heavily. We supply the plants with the water they need and add about 30 percent to the top. We use this to flush the salt out of the root zone again. Clarified." There is enough wastewater and it doesn't cost much.

The global olive oil boom is also causing problems elsewhere. And later in the mill, when the oil is pressed from the harvested fruits in winter. There has been a new technology for several years. In addition to solid and muddy waste, it now also produces wastewater - albeit one that must be assessed as critical. Gabriele Schaumann, Professor of Environmental and Soil Chemistry at the University of Koblenz-Landau:

"More oil from the olives, that was the idea. And a lot of small family businesses in Israel, in Palestine, in Greece and also, I think, in Spain and Italy have switched. And only then did you notice that the wastewater, that arises, is extremely dangerous and simply cannot be disposed of with the normal sewage process. "

The waste water with the olive remains is extremely acidic. It also contains a lot of organic substances. Their breakdown uses up large amounts of oxygen. Schaumann:

"Then the systems overturn. And now the sewage treatment plants no longer accept that."

In this respect, nobody really knows at the moment what to do with the wastewater. The idea now is to spread it again in the olive tree plantations themselves. Because there are also plenty of nutrients in the olive remains. Gabriele Schaumann's working group is currently researching the conditions under which this could work. The season is crucial, says Gabriele Schaumann:

"We are currently trying to develop methods of how we can apply this in spring, where the biological activity in the soil is very high and where the organic substances can be broken down."

The wastewater from the oil mills would then also have a fertilizer effect. According to the chemist, the results so far are very promising:

"I have to look for a place to store it. Then I'll spread it out on the ground and my olives will grow better afterwards than before."