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Increasing the productivity of sunflower through efficient use of non-saline and saline water irrigation in the Ganges Delta

Mila, Afrin Jahan (2021) Increasing the productivity of sunflower through efficient use of non-saline and saline water irrigation in the Ganges Delta. PhD thesis, Murdoch University.

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Climate change and sea-level rise have caused increases in soil and water salinity and freshwater scarcity in Coastal Bangladesh in the Ganges delta. This has greatly increased the risks associated with dry season cropping. Therefore, increasing the productivity of dry season crops (like sunflower) depends on the proper management of non-saline and saline water irrigation. Three experiments were conducted, mostly in Khulna, Bangladesh, including (i) a surface and groundwater survey on salinity and water availability, (ii) determination of crop sensitivities to saline water irrigation through pot studies, and (iii) studies on the combined use of non-saline and saline irrigation water in field experiments. It is found that the salinity of canals and ponds started to increase after February and reached a maximum by mid-April. The salinity of ponds and groundwater was less than the salinity of rivers and canals (without bunds). Cumulative evaporation, water extraction and saline water intrusion were the most important factors increasing water salinity and decreasing the volume of stored water. Pot experiments showed that sunflower was most susceptible to salinity during flowering. Yield reductions were related to both a reduction in mature seed number and seed size. Yields were positively related to photosynthesis and negatively related to Na/K ratios. In the field, limited use of freshwater at the initial stages and increasing use of brackish/saline water at the latter stages increased the freshwater productivity of sunflower 4–fold. This freshwater productivity (FWP) concept is particularly suitable for the saline areas, to focus on increasing the value derived from the use of limited volumes of fresh water, supplementing this with the use of saline water. Increasingly negative solute potentials and increasing soil salinity (EC1:5) at 15–30 cm and 45–60 cm soil depths had the greatest adverse effects on the yield of sunflower in the field. Around 40–79% of the salt added in the irrigation water could not be accounted for in the 0–60 cm layer of soils suggesting that it moved to soil layers deeper. It is recommended that non-saline water be used to irrigate sunflowers when plants are most sensitive to salinity, but slightly to moderately saline water could be used at other growth stages without adversely affecting yield. The sustainability of this practice in the long term needs further investigation.

Item Type: Thesis (PhD)
Murdoch Affiliation(s): Agricultural Sciences
Supervisor(s): Bell, Richard, Barrett-Lennard, Ed and Kabir, Enamul
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