Optimising Direct-Seeded Basmati Rice for sustainable water use

Rice, a staple food for billions, faces significant challenges in its production, particularly in water-scarce regions like India. Traditional transplanting methods, while widely used, are water-intensive and labour-demanding. This has led to a shift towards Direct Seeding of Rice (DSR), a method that involves sowing seeds directly into the field, eliminating the need for nursery preparation and puddling.

A recent paper by Diljeet Kaur “Growth and productivity of direct-seeded basmati rice (Oryza sativa L.) as influenced by sowing dates and irrigation schedules in north-western India” looks at the potential of direct-seeded basmati rice to enhance water use efficiency in basmati rice cultivation. It explores the impact of sowing time, irrigation scheduling, and other factors on yield and water productivity.

However, optimising DSR for maximum water efficiency and yield remains a challenge. Key factors influencing DSR success include sowing time and irrigation scheduling. Early sowing can lead to increased water demand due to higher temperatures, while late sowing can delay the subsequent wheat crop. Therefore, striking a balance between these two factors is crucial.

To further improve water use efficiency in DSR, researchers are focusing on accurately estimating crop water requirements and developing precise irrigation scheduling techniques. By understanding the water needs of the crop at different growth stages, farmers can optimise irrigation practices and minimise water waste.

Ultimately, the successful implementation of DSR for basmati rice can contribute to sustainable rice production, alleviate water scarcity, and ensure food security in India and other regions facing similar challenges.

Materials and methods

The experiment was conducted at Punjab Agricultural University, Ludhiana, India, over two years. The region has a sub-tropical to semi-arid climate with hot summers, humid monsoons, cold winters, and mild springs. The soil is sandy loam with low organic carbon content.

The experiment used a split-plot design with six sowing date and irrigation timing combinations. The experiment was laid out in split plot design keeping combinations of two sowing dates (June 10 and June 20) and time of first irrigation (7, 14 and 21 days after sowing) in main plots and subsequent irrigation schedules at 1.25, 1.50 and 1.75 irrigation water/crop evapotranspiration, irrigation water to crop evapotranspiration ratio in sub-plots. Crop water requirements were estimated using the Penman-Monteith equation, and irrigation was applied based on depth of irrigation water/crop evapotranspiration ratios.

A deeper dive into the research on Direct-Seeded Basmati Rice

The provided research offers valuable insights into optimizing direct-seeded basmati rice cultivation. Here's a more detailed breakdown of the key findings:

Sowing date and first irrigation

• Flexibility in sowing: Delaying sowing by 10 days had minimal impact on yield and growth parameters, providing farmers with a wider sowing window. This flexibility can be advantageous in regions with unpredictable weather patterns.

• Strategic first irrigation: Postponing the first irrigation to 21 days after sowing significantly reduced water usage without compromising yield. This practice can be particularly beneficial in regions with limited water resources. By delaying the initial irrigation, the crop is allowed to establish a robust root system, which improves its water-use efficiency and drought tolerance.

Subsequent irrigation schedules

• Balancing yield and water use: The study highlights the importance of balancing irrigation frequency with water use efficiency. An IW/ETc ratio of 1.50 was found to provide a good balance between yield and water savings. This approach ensures that the crop receives adequate water to meet its physiological needs without excessive water application.

• Diminishing returns of excessive irrigation: Increasing irrigation frequency beyond IW/ETc of 1.50 did not lead to significant yield increases but increased water consumption and deep percolation losses. This suggests that over-irrigation can lead to inefficient water use and potential environmental issues.

Economic considerations

• Cost-effective practices: Delaying the first irrigation and optimising subsequent irrigation schedules can lead to significant cost savings, primarily due to reduced energy consumption for pumping water.

• Water productivity: The study emphasises the importance of water productivity, which measures the amount of crop produced per unit of water consumed. IW/ETc of 1.25 and 1.50 were found to be more water-efficient than 1.75. By optimizing irrigation practices, farmers can improve water productivity and reduce production costs.

Implications for farmers and policymakers

• Flexible cropping calendars: Farmers can adopt more flexible sowing schedules, especially in regions with variable rainfall patterns. This can help to mitigate the risks associated with adverse weather conditions.

• Precision irrigation: Implementing precise irrigation scheduling techniques, such as soil moisture monitoring and sensor-based irrigation systems, can optimise water use. These technologies can help farmers to apply water only when and where it is needed, reducing water waste.

• Water-saving technologies: Promoting the use of water-saving technologies like drip irrigation or laser land leveling can further enhance water use efficiency. These technologies can significantly reduce water losses through evaporation and deep percolation.

• Policy support: Government policies can incentivize the adoption of water-saving practices and promote research and development in this area. By providing subsidies, tax breaks, or other incentives, policymakers can encourage farmers to adopt sustainable agricultural practices.

Future research directions

• Climate change impact: Future research should investigate the impact of climate change on direct-seeded basmati rice, including changes in temperature, rainfall patterns, and pest and disease incidence. This information can help farmers and policymakers to adapt to changing climatic conditions.

• Soil health and nutrient management: Exploring the role of soil health and nutrient management practices in improving water use efficiency and crop productivity. By maintaining healthy soils, farmers can improve water infiltration, nutrient retention, and overall crop resilience.

• Alternative water sources: Investigating the potential of alternative water sources, such as rainwater harvesting and recycled wastewater, for irrigation. These alternative sources can help to supplement conventional water sources and reduce dependence on groundwater.

• Economic and social aspects: Assessing the socio-economic implications of water-saving technologies and practices, including the impact on rural livelihoods and food security. It is important to consider the economic and social factors that influence farmers' adoption of new technologies and practices.

By understanding the intricate relationship between sowing dates, irrigation schedules, and water use efficiency, farmers and policymakers can make informed decisions to optimise basmati rice production while conserving precious water resources.

Conclusion

Delaying sowing or the first irrigation did not significantly impact grain yield. However, postponing the first irrigation to 21 days saved 17.1% of irrigation water. Subsequent irrigations at IW/ETc of 1.50 increased grain yield compared to 1.25, but further increasing frequency to 1.75 did not. While 1.75 IW/ETc had the highest net returns, 1.50 provided a good balance between yield and water use efficiency.

These findings suggest that strategic irrigation scheduling can significantly improve water use efficiency without compromising yield.