Features: Saline Soils

Partners in the Lab

Scientists Athar Khan and M'hamed El Khadir share a common goal. They come from countries - Pakistan and Morocco - where saline lands are widespread barriers to agricultural development. The goal they share is to see the fields become productive through contributions they can make back home.

"We need to better understand the composition of our own soils, and that will help us tell farmers how and where different types of plants can grow best."

For several months this year, they worked as scientific fellows with the IAEA's Rebecca Hood, a soil scientist from the United Kingdom, at the Agriculture and Biotechnology Laboratory, a joint FAO/IAEA branch of the Agency's Seibersdorf Laboratories near Vienna, Austria. Under the IAEA's project on saline soils, Mr. Khan and Mr. El Khadir conducted separate experiments whose results could help their countries reclaim wastelands.

Mr. El KhadirMr. El Khadir, a microbiologist with Morocco's National Institute of Agronomic Research (INRA), studied the decomposition of organic matter in soils. Using a method called "dual labelling" with the stable isotopes nitrogen-15 and carbon-13, he tracked the rate at which different types of organic materials decomposed in saline soils.

Mr. El Khadir used tropical nitrogen - fixing seedling trees grown in the Seibersdorf greenhouse. He then labelled them using carbon-13 and placed the seedlings inside a small rectangular gas chamber sealed in plastic. More difficult was assessing how the breakdown of labelled organic matter affected soil conditions. The work entailed reviewing and interpreting extensive data from samples measured by the laboratory's mass spectrometer. The highly sensitive analytical instrument measures about 10,000 samples a year under projects supported by the Soil Science Unit.

"The experiments will help me in my research at INRA," says Mr. El Khadir. "We need to better understand the composition of our own soils, and that will help us tell farmers how and where different types of plants can grow best."

Khan Research

Mr. Khan's research was similarly directed to helping his country more productively use saline lands, which extend to more than six million hectares nationwide. A plant physiologist with Pakistan's Nuclear Institute of Agriculture, Mr. Khan's research at Seibersdorf focused on studies of wheat, a staple crop in Pakistan. He sought to learn more about a technique known as "carbon isotope discrimination" and its potential as a screening tool for salt-tolerant varieties of wheat. His research built on work done at Seibersdorf by a fellow Pakistani, Ms. Robina Shaheen, an IAEA associate professional officer who studied wheat and rice varieties.

Mr. Khan's experiments involved determining the relationship between salt tolerance and carbon-12 and 13 ratios in more than 50 varieties of wheat that he brought from Pakistan and planted as seedlings in soils containing different levels of salinity. Carbon measurements were done using the Laboratory's mass spectrometer. Mr. Khan also played a key role in developing new preparation methods that would allow materials to be analyzed using a commercial instrument called a breath test analyzer. The Soil Science Unit is seeking to develop the instrument as a low-cost measurement system for carbon isotope studies.

"Screening for salt tolerance in cereals requires reliable techniques," says Mr. Khan. "Doing it under field conditions is difficult and involves many complex factors that take a long, long time to study".

If research singles out carbon-13 as a useful criterion, it could lead to a rapid and inexpensive screening technique for agricultural laboratories in Pakistan and other countries facing salinity problems.

"Pakistan's population is growing fast and we need to increase food production," says Mr. Khan. "Salinity affects about 50% of our irrigated land, so we have to cultivate plant varieties that can grow in saline soils."

Dr. Rebecca Hood

Carbon-13 applications are common as a tracer and in studies investigating the process of photosynthesis in plants, says the IAEA's Dr. Hood. "We know it can be a useful tool in the selection of plant varieties that tolerate drought," she says. "If it turns out to be a reliable technique for screening salt tolerance, that would be a big step forward."

Photo credits: D. Calma/IAEA