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Effect of Water-saving Irrigation Practices on Soil Chemical Properties and Rice Yield in Gia Lam District, Hanoi Province
Thesis Abstract:
Increasing demand for rice and decreasing water diversions to agriculture urge for higher water productivity in rice production systems. One way to deal with this challenge is using water-saving regimes on a field scale. The main objective of this study was to quantify the effects of water-saving regimes on water productivity, soil chemical characteristics, and crop yield. The role of subsurface hydrology was studied to assess the effects of water saving on water balance.
Field experiments were conducted during the spring season at Hanoi Agricultural University in Gia Lam District, Hanoi Province, Vietnam. In the experiment comparing alternate wetting and drying (AWD) and saturated soil (approximately field capacity) regimes, soils remained dry for several days before reirrigation with continuous submergence (CS). The implementation of a recommended water regime of AWD and saturated soil with mid-season drainage did not lead to very dry soil conditions during the continuous flooding (CF) periods. Shallow ground water table remained within the root depth of the soil profile and soil water potentials were never much below -10 kPa.
Biomass and yield did not significantly differ between AWD, saturated soil, and CF; but water productivity was higher under AWD and saturated soil than under CF in the experiment.
There were no significant differences in the soil chemical characteristics under CF, AWD, and saturated soil regimes.
With reference to CF, the percentage of total water input from AWD was 6-14 percent while 10-17 percent for saturated soil. On the other hand, the amount of irrigation water saved under AWD was 10-15 percent and 15-20 percent for saturated soil.
This study was able to identify the most suitable water-saving regimes given the soil type, weather conditions, and predominant groundwater table depth. Other socioeconomic factors may, however, influence farmers’ decision to adopt this regime; namely, relative scarcity of water, price of water and rice, demand for rice, government policies, etc.; but these are outside the scope of this research.