Abstract
A drip irrigation system with plastic mulch film was evaluated in terms of growth, yield, and water productivity (WP) using three leading paddy rice cultivars (Japonica) in the Kanto area of Japan. A cultivation with drip irrigation and plastic film mulch in the upland field (DI) and continuous flooding cultivation in a paddy field (CF) were conducted in 2015 (DI) and 2016 (DI and CF). The amounts of irrigation and total water supply (irrigation and precipitation) were 715 mm, 599 mm, and 905 mm and 1620 mm, 1379 mm, and 1687 mm for DI in 2015, DI in 2016, and CF in 2016, respectively. The percentages of irrigation for DI in 2015 and 2016 compared to those of CF were 79% and 66%, respectively. The grain yields in 2015 were higher than those in 2016 for DI. The DI in 2016 showed significantly lower grain yields compared to those of CF, representing 74% to 85% of the CF which were attributed to lower leaf area indexes in DI. There was no significant difference in WP between DI and CF, between years and among cultivars, ranging from 0.25 to 0.30 kg m<sup>-3</sup>, showing an offset of the reduction in irrigation water by lower yields in DI. The rice cultivation system under drip irrigation with plastic film mulch showed a large water-saving effect, no physiological damage due to water stress and a slight reduction of grain yield compared to that of the paddy field.
Highlights
As human populations and economies grow, it has become evident in the last few decades that freshwater scarcity is becoming a threat to the sustainable development of human society [1]
The mean air temperature in 2015 was low from June to early July owing to continuous rainy days, and increased drastically in the middle of July
The high air temperature continued for one month, decreased rapidly after the middle of August compared to that in an average year (Figure 1)
Summary
As human populations and economies grow, it has become evident in the last few decades that freshwater scarcity is becoming a threat to the sustainable development of human society [1]. Several practices are designed to reduce water use and increase water use efficiency in rice cultivation, including saturated soil culture (SSC), alternate wetting and drying (AWD), aerobic rice (AR) and drip irrigation (DI). These systems have the possibility to reduce global warming potential (GWP), especially that from rice paddy methane emissions, which have been estimated to contribute 15%-26% of the total global anthropogenic emissions[4]. In the AR system, specially adapted input-responsive AR varieties are grown under dryland conditions with or without supplemental irrigation[8] This system could reduce water inputs by 30%–50% with a 20%–30% reduction in yield compared to that in flood systems
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