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Wheat growing on saline soils  
By Zulfiqar Ali

Pakistan's 70 per cent population living in rural areas is directly related to agriculture. Their prosperity is dependent on cotton, wheat, rice, sugar cane and
maize production.

Most of the area is commanded by extensive canal irrigation system. Irrigation water contains different species of salts in varying amounts. Water, due to
weather conditions, is evaporated rapidly leaving salts to accumulate at soil surface.

Insufficient precipitation keeps these salts unleached which according to a report, has affected about 62 per cent of the canal commanded area with
moderate to severe salinity. Another survey revealed that about 6.3x106 ha of the irrigated land had gone out of cultivation.

In addition, over 70 per cent of groundwater, pumped mainly in canal commanded areas, is of poor quality. Economic losses due to the decreased
agricultural productivity in salt-affected areas are estimated at Rs20 billion per annum.

Wheat, an important cereal crop throughout the world, and a staple food in Pakistan is grown on an area of about 8.034 million ha giving production of
about 19.18 million tonnes annually.

Adoption of high yielding varieties in canal irrigated areas during the past two decades did boost it's production from 4.9 million tonnes in 70s to 19.18
million tonnes during 2002-2003.

With an average yield of 2.4 tonnes per hectare, the country occupies 59th position in the world. In addition to other agronomic factors affecting wheat yield,
loss of soil fertility, water scarcity, biotic stresses, abiotic stresses like soil salinity in canal commanded areas, are major constraints of low wheat production.

Soil salinity is a limiting factor in allowing exploitation of crops and with an increasing phenomenon it poses threat to the survival of human populations.
Due to salination on huge acreage and increasing demand for food supply, the government, in the past, recommended preventive measures for bringing the
wastelands under cultivation.

Various soil amendments like gypsum, sulphur, and sulphuric acid were applied to leach the salts down in soil. Leaching through irrigation requires extreme
care as this should not add to underground water table.

In addition, the government started different reclamation projects like the Salinity Control and Reclamation Projects (Scarp), and constructed drainage to
lower or stabilize the water table. The approach had been effective in controlling the salinity and water logging but the escalating cost of energy did
hamper in the running of these projects.

Another concept i.e., "Saline Agriculture" also suggests the use of saline lands to generate income from derelict lands without spending huge amounts on
drainage and reclamation work.

This has been demonstrated successful by planting salt tolerant trees and shrubs e.g., Atriplex and Eucalyptus on-farm trials in the affected areas. It suggests
improvement through selection and breeding.

Another, which appears more feasible is the development of crop cultivars suitable for the areas affected by salinity. called "biological/genetic approach".
This approach is cheaper and has been emphasized by numerous research workers.

One of the limitations in transferring genes for stress tolerance through genetic approach is lack of good tests for tolerance because the physiological
mechanisms involved are not fully understood.

Keeping in view the increasing consumption of food grains, there is a need to utilize huge acreage of waste lands for agriculture purpose. Cultivation of
wheat crop in the areas affected by salinity would contribute towards increasing production.

Studies were undertaken at the University of Agriculture, Faisalabad in order to assess genetic potential in wheat for improving salinity tolerance with the
objective of generating information on the genetic mechanism controlling the salinity tolerance.

It was revealed that significant genetic potential in plant material exists which may be exploited further to develop more salt tolerant genotypes for the use
of salty areas for cultivation.

The phenomenon of salinity tolerance is a complex character, further showing that the prospects of improving the character through selection and breeding
are considerable. The solution culture technique has been useful to isolate highly tolerant and highly sensitive accessions, measuring root length in
salinized nutrient solution.

This rooting technique may be employed for screening a large number of genotypes available in segregating generations. The information generated by
these studies are advantageous and encouraging for research workers in selecting plants having longer roots at the seedling stage, leading to the
development of plant material suitable for saline conditions. 

Courtesy:The DAWN;

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