By DR M. JALALUDDIN
n order to avert water shortage; methods such as lining of water courses, sprinkling and drip irrigation, roof harvesting of rainwater followed by pitcher irrigation and storage of rainwater in pits and ponds for the optimal use of water for irrigation have been suggested.
This appalling situation calls for the application of an agricultural biotechnology for increasing the uptake of available water in soil which cannot be had by plant roots. A fertile farm soil is a living system with characteristic physico-chemical properties and diverse microbial population.
Of the many soil microorganisms, some are decomposers, some parasites while others are beneficial. There is a special group of microorganism known as mycorrhizas (myco-fungus, rhiza-root) which live symbiotically in association with 90 per cent of plants all over the world.
A threadlike structure called mycelium produced by the mycorrhizas ramifies extensively into soil around plant roots and enters into its roots. Plant roots absorb water from soil but the roots cannot go far enough into soil to absorb the water and nutrients present in soil aggregates (crumbs) on account of its shortness and fewer in number compared to the mycorrhizal mycelia.
The mycorrhizal mycelia ramify extensively in soil and absorb nutrients dissolved in water till the last drop of water is present in the region of plant roots. The mycorrhizal mycelia, in fact, assume the function of additional roots for host plants. There is a dramatic effect on the growth and yield of plants whose roots harbour mycorrhizal fungi as compared to non-mycorrhizal plants. The mycorrhizas are inoculated in soil for the biological phosphorus fixation in plants and, inter alia, it improves the water supply to plants.
It is for this reason that mycorrhizal plants tolerate water stress (drought) better than non-mycorrhizal plants. At this critical stage when water resources are shrinking there is an urgent need to increase symbiotic relationship between mycorrhizas and crop plants.
Effective mycorrhizal cultures specific to host plants can be prepared biotechnologically and inoculated in farm field soil as being done in Australia.
This technology is useful in climatic zones which are semiarid to arid. Plants in that zone tolerate high temperature and scarcity of water. This technology has turned deserts into farmlands in West Asia.
The acquisition of mycorrhizal biotechnology and its application in farm fields of Sindh, southern Punjab and Balochistan is the need of the hour to minimise the agricultural crisis due to the shortage of water.
We should make the best use of existing water resources biotechnologically from farm field soils which cannot be absorbed by plant roots.
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