Abstract
Taiwan’s average annual rainfall is high compared to other countries around the world; however, it is considered a country with great demand for water resources. Rainfall along with alternate wetting and drying irrigation is proposed to minimize water demand and maximize water productivity for lowland paddy rice cultivation in southern Taiwan. A field experiment was conducted to determine the most suitable ponded water depth for enhancing water saving in paddy rice irrigation. Different ponded water depths treatments (T2 cm, T3 cm, T4 cm and T5 cm) were applied weekly from transplanting to early heading using a complete randomized block design with four replications. The highest rainwater productivity (2.07 kg/m3) was achieved in T5 cm and the lowest in T2 cm (1.62 kg/m3). The highest total water productivity, (0.75 kg/m3) and irrigation water productivity (1.40 kg/m3) was achieved in T2 cm. The total amount of water saved in T4 cm, T3 cm and T2 cm was 20, 40, and 60%, respectively. Weekly application of T4 cm ponded water depth from transplanting to heading produced the lowest yield reduction (1.57%) and grain production loss (0.06 kg) having no significant impact on yield loss compared to T5 cm. Thus, we assert that the weekly application of T4 cm along with rainfall produced the best results for reducing lowland paddy rice irrigation water use and matching the required crop water.
Highlights
Global agriculture is faced with the tremendous challenge of providing enough food for a growing population under increasing water scarcity
Rainfall represented 3.87, 2.58, 1.93, and 1.55% of irrigation water applied in treatments The weekly application of 2 cm (T2 cm), T3 cm, The 4 cm (T4 cm), and The application of 5 cm (T5 cm), respectively
Rice sensitivity to water stress was observed in plant height reduction at panicle initiation (T2 cm and T3 cm) and heading stage (T2 cm) as drought stress tend to induce a decline in net photosynthesis and reduced growth rate through inhibition of cell elongation or cell division
Summary
Global agriculture is faced with the tremendous challenge of providing enough food for a growing population under increasing water scarcity. Fresh water for irrigation is becoming scarce because of population growth, increasing urban and industrial development, and the decreasing availability resulting from pollution and resource depletion (Bouman, 2007; Chapagain & Riseman, 2011; Edward & David, 2008; Thakur et al, 2011). Irrigated rice production is the largest consumer of water in the agriculture sector, and its sustainability is threatened by increasing water shortages (Thakur et al, 2011). Agriculture water productivity directly affects crop productivity; various watersaving techniques and methods have been developed for rice producers to minimize water demand and maintain acceptable yield.
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