Innovative Rice Growing Technique Saves Resources & Reduces Emissions
By Virender Kumar, IRRI Senior Scientist and DSRC Coordinator, Ajay Panchabhai, IRRI Senior Manager, Business Development, & Remy Bitoun, IRRI Head of Tech Transfer
Rice is already a staple food for over half of the world’s population. With 25% more rice projected to be needed in the next 25 years to meet global demand, the challenge is how to grow it more sustainably.
Currently 90% of the world’s rice is produced in Asia, mainly using the Puddled Transplanted Rice (PTR) method in which rice is first sown in a nursery before the seedlings are manually transplanted into a puddled (wet-tillage) and flooded field.
Unfortunately, PTR is a very resource-intensive and uneconomical method as it consumes a large amount of increasingly scarce and expensive labour, water and energy. It’s also a major contributor to methane emissions, a global warming greenhouse gas (GHG).
In recent years Direct Seeded Rice (DSR) has emerged as an economically viable alternative to PTR that saves scarce labour, water, and energy resources, reduces GHG emissions and drudgery, and increases yields of rotational non-rice crops.
Issues and Opportunities in Asia
There are three types of DSR: dry-DSR, wet-DSR, and water seeding. In dry-DSR, dry seeds are sown in non-puddled soil, whereas in wet-DSR, pre-germinated sprouted seeds are sown in puddled soil. In water seeding, pregerminated seeds are broadcasted in the standing water of puddled or non-puddled soil.
In many Southeast Asian countries, farmers have shifted from PTR to DSR, whereas in China and South Asian countries, with the exception of Sri Lanka, adoption has been low (Fig 1). In countries where DSR is widely adopted, many currently used DSR farming practices are less efficient and precise than the best practices, leaving considerable opportunities to improve efficiencies, increase yields, and reduce the environmental footprint of rice by improving the method.
Figure 1: DSR Area (% of total rice area) in selected Asian countries
Most farmers in Southeast Asia, for example, establish their DSR using the broadcast method with high seed rates (100 to 350 kg ha-1) of their own saved seeds. The cost of high seed rate is one of the bottlenecks for adopting good quality seed of inbred or hybrid rice varieties in DSR systems. By using precision planters and low seeding rate, farmers could switch to good quality seed in DSR.
Despite the multiple economic and environmental benefits, DSR also has a few risks and constraints that are limiting its wider-scale adoption and in achieving optimal yields. These include: poor and uneven crop establishment due to inundation or drought during crop establishment and damage from birds, rodents, and insects; higher weed infestation and herbicide resistance leading to the risk of higher yield losses; limited knowledge on precision irrigation scheduling and nutrient management; and a lack of cultivars developed for DSR conditions.
To help realize the full potential of DSR, these existing research knowledge gaps need to be closed and scalable solutions developed to overcome the current challenges.
A New Platform for Promoting DSR
The Direct Seeded Rice Consortium (DSRC) was established in December 2017 by the International Rice Research Institute (IRRI) as a public-private multi-stakeholder platform, with IFA as a member, to better research and scale up DSR in Asia.
Specific objectives include: developing robust mechanized DSR systems with low seeding rates to enable farmers to use high-quality inbred or hybrids; developing precise weed, water and nutrient management practices including ICT-based decision tools; reducing risks by agronomic and breeding solutions, and by proper targeting using GIS approaches; identifying suitable varieties for DSR; and catalyzing the wide-scale adoption of mechanized and precise DSR with cost-effective access to scale-appropriate machinery and technologies such as drones and ICT-based decisions tools.
Nutrient Management Prospects
For the fertilizer industry and agronomists, the move to DSR presents new opportunities for rice production, such as effective nutrient and water management strategies to reduce emissions of methane and mitigate increased emissions of nitrous oxide.
Nutrient use efficiency could be further improved by using fertilizer products such as slow/controlled-release and foliar fertilizers, precise application methods such as drones and spreaders, and applying site-specific nutrient management principles.
The shift towards more aerobic conditions also reduces the bioavailability of micronutrients, with iron deficiency an issue for continuously grown dry-DSR, for example. These emerging micronutrient deficiencies could present interesting new possibilities for fertilization.