"Drainage cannot be done individually"

Ildefonso Pla, considered a world authority on water quality and salinity, spoke with an Information Letter about this problem in the world and Colombia.

Ildefonso Pla Sentís, agronomist, doctor in Soil Science and specialist in Soil and Water Management and Conservation, was in the course-workshop on models, prevention and recovery of soils with salt problems, organized by Tecnicaña with the support of Cenicaña. During the course-workshop, Pla presented the Salsodimar model for the prediction and control of soil salinity and sodification. Salsodimar is a flexible methodology that can be adapted to climate and cultivation conditions and allows establishing how irrigation water should be managed and the type of drainage to implement. The model is the product of successive approaches based on experiences and validations accumulated in different agro-ecological zones in the last 30 years.

The issue of soil salinization has been gaining spaces for discussion. How serious is this phenomenon in the world?

It is a problem that tends to be more serious, because there is less and less water to use in agriculture and more and more water of poorer quality must be used. Salinization is a phenomenon that has always existed and that is more noticeable in some nations; perhaps that is not the case in Colombia because this is a country with enormous water wealth; but it is evident that there is not enough water to irrigate, that 40% of the world's food is produced in irrigated agriculture and salinization makes the soils unproductive.

In addition to salinization, there is a phenomenon that destroys the structure of the soil: sodification. This is much more serious, because salinization is resolved by washing the salts, but once the soil structure has been destroyed it is very difficult to recover it.

If sodification is so serious, why hasn't it been given the attention it deserves?

Because it doesn't look that fast, and it develops very slowly. There are countries in the world where the experience has been serious. India, for example, which is one of the countries that has the most area under irrigation, has enormous lands that have been sodified over the centuries and now society faces enormous problems in using and recovering them. Closer is the case of Argentina, where the entire water regime for soybean cultivation was changed on lands that were used for pasture and that consumed more water. Today there is an excess of water that goes to the low areas, the water table has risen and the cattle were sent to those deteriorated sites. The country faces a serious problem, in which meat could eventually be imported, which is a situation of national pride.

How do you see the situation in Colombia?

I have been coming to Valle del Cauca for many years. I visited the Ciat grounds when it was being built because they were saline soils. There I learned about the salinity problems of Valle del Cauca and they have worsened because the cultivation of sugarcane was extended to lands with poorer drainage, I even think that some that were with rice are now used for sugarcane. Over time these soils can become waterproof in depth and it is already noticeable in some places that the roots of the sugar cane remain superficially, which implies watering more frequently, applying more fertilizer ...

But work has been done on efficient water management ...

People forget that managing irrigation also includes drainage, and drainage was left as secondary. But this not only happens here, but everywhere with terrible consequences. Drainage is used to eliminate excess water or to prevent the rise of groundwater, which creates problems on surfaces, and this implies taking into account rain, irrigation water, water quality ... that is, integrating a series of factors in each case.

But the drainage cannot be done individually either, nor on behalf of each farm because it creates a problem for the neighbor. This must be planned at the basin or micro-basin level, and some higher body must act as a coordinator.

Which actor would assume that role?

Industry must act as an advisor. The industry must offer technical advice that teaches the drainage system to the grower. In the 60s in the Imperial Valley, a valley in southern California, a case of salinization occurred. It was a huge expanse of land in which reclamation work began, washing and establishing a drainage system. The United States Soil Conservation Service, which depended on the government, was in charge of the drainage design; the field studies were contracted with another company and, additionally, another entity coordinated the correct operation of these drains. I bring this example to show that any measure has to be taken comprehensively.

What would be your call to the cultivator?

It will always be difficult to convince someone to take action in the face of a reality that will present itself in 20 years, but from now on, cultivators can act. I am sure that in some places only by improving the drainage conditions the effects on production will be noticed immediately.

I had the opportunity to work with producers in Argentina in areas with deteriorated soils. There, in the fields, we made holes, so that they could see what was happening on the ground. The key is that they see the problem, once they notice it they tend to be more aware.

Information letter
Year 1 / Number 2 / August 2013

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