New Delhi/Chennai, Dec. 23
SCIENTISTS working on salinity-affected soils in coastal Tamil Nadu after the December 26 tsunami say the recent rains and floods have helped to bring down the salinity.
But the problem has not entirely been solved as the degree of salinity varies widely depending on local conditions. It could be a few years before the salinity problem is brought down to levels before that of the tsunami.
"The heavy rains will definitely flush out the salinity from the soil and water bodies, reducing the salinity in the soil to quite a great extent. Same would be their impact on the water table below the soil as well," said Dr A.K. Singh, Director, Indian Agricultural Research Institute (IARI), when contacted by Business Line.
As it is, rains in the South would have washed out the salinity, but the process of desalination would get heavily accelerated owing to the excess rainfall, added Dr Singh.
According to a scientist at the M.S. Swaminathan Research Foundation, which is working in this area, their team is looking at the problem at specific locations in Nagapattinam. The soil pH, a measure of salinity, ranged between 6.1 and 8.5 before the tsunami, and after the disaster it was observed to be 8.8 or higher. But there has been a wide variation depending on the duration that seawater stagnated and the nature of the soil.
The solution was to let the salts leach away by holding freshwater in the saline soil so that the salts either get washed away in the neighbouring canals or go to the subsoil area away from the root zone of the crops. But the salts that get into the subsoil could rise to the surface if the soil is allowed to dry.
Here is where the rains and floods have helped. The large flow of freshwater has helped to wash away the salts and to keep the soil moist for an extended time, but it is not yet the final solution, which would take time, the scientist cautioned.
The summer crops are likely to be benefited owing to the fall in salinity, Dr Singh said.
But he is guarded on the likely impact of rains on aquaculture. "The flooding caused due to these rains are likely to impact the aquaculture process negatively," he said.
Shrimp farms in Nagapattinam and Sirkazhi have been affected by the heavy inflow of freshwater, flooding and severe drop in temperature. Farms in Sirkazhi near Cuddalore, one of the severely flood affected areas, have been wiped out.
In other areas the severe drop in temperature during the season has resulted in outbreak of viral diseases, say farmers.
According to Mr Ali Hussein, President, Sirkazhi Aqua Farmers Association, shrimp farms along the banks of the Coleroon River had been severely affected - stocks of shrimps washed away and tank bunds destroyed. Equipment such as aerators have also been washed away. Initial estimates of shrimp losses are estimated at about Rs 3-4 crore. During the floods, the Coleroon carried most of the floodwaters and helped avoid extensive flooding of the Cauvery delta areas.
Shrimp farms on the south bank are in Nagapattinam and South Arcot districts and those along the north bank in Chidambaram and these were some of the areas worst affected by the floods.
Mr P. Gangadhar, President, Nagapattinam Aqua Farmers Association, said apart from the flood damage, rapid drop in temperatures had also caused an outbreak of viral disease in areas other than those affected by the floods. Farms in Nagapapattinam, Velankanni, Vedaranyam and Pattukottai have been affected by the disease outbreak. The farmers would recommence stocking in February March 2006, he said.