Vol. 12, Issue 4 (2023)

Author(s):
PK Singh, RK Naresh, Rajan Bhatt, Himanshu Tiwari, Omkar Singh, Akashdeep Singh, Rojalin Hota and Rahul Kumar

Abstract:
The water crisis is threatening the sustainability of the irrigated rice system and food security in Asia. Our challenge is to develop novel technologies and production systems that allow rice production to be maintained or increased in the face of declining water availability. This review paper introduces principles that govern technologies and systems for reducing water inputs and increasing water productivity, and assesses the opportunities of such technologies and systems at spatial scale levels from plant to field, to irrigation system, and to agro-ecological zones. We concluded that, while increasing the productivity of irrigated rice with transpired water may require breakthroughs in breeding, many technologies can reduce water inputs at the field level and increase field-level water productivity with respect to irrigation and total water inputs. Most of them, however, come at the cost of decreased yield. More rice with less water can only be achieved when water management is integrated with direct-seeded rice (DSR) technique is gaining popularity because of its low input demand compared to puddle transplanted rice (PTR). It is done by sowing pre-germinated seeds in puddled soil (wet-DSR), standing water (water seeding), or dry seeding on a prepared seedbed (dry DSR). Alternative tillage and rice establishment options should aim at less water and labor to produce similar or improved yields compared with traditional puddled-transplanted rice cultivation. DSR requires less water and labor (12–35%), reduces methane emissions (10–90%), improves soil physical properties, involves less drudger and gives comparable yields. The AWD technology required about 22% less water compared to the continuous standing water irrigation system. Depending on the rice varieties and season of the rice cultivation, greenhouse gas emissions were 13%–41% less under AWD compared to continuous standing water. Water savings using alternate wetting and drying (AWD) ranged from 42.8 to 53.7% of total water input in comparison with continuous flooding (CF), without yield loss, but there was little difference in water input among AWD treatments. Due to shorter duration of growth in the main field, water input with 30-d-old seedlings was lower than with younger seedlings, but with a corresponding yield loss. Total water productivities in AWD treatments were higher than those with CF. Moreover, non-puddled transplanting of rice saves 35% of the net life cycle greenhouse gases (GHGs) compared with the conventional practice by a combination of decreasing greenhouse gases emissions from soil. Dry-seeded rice technology offers a significant opportunity for conserving irrigation water by using rainfall more effectively. The future of rice production will therefore depend heavily on developing and adopting strategies and practices that will use water efficiently in irrigation systems. This review paper emphasizes the need for integrating various water-saving measures into practical models and for conducting holistic assessments of their impact within and outside irrigation systems in the water basin.