Rice husk soil amendments as a GHG-mitigating piece of the circular rice production system

Authors: RUNKLE, BENJAMIN - University Of Arkansas; SEYFFERTH, ANGELIA - University Of Delaware; REID, MATTHEW - Cornell University; LIMMER, MATTHEW - University Of Delaware; MORENO-GARCIA, BEATRIZ - University Of Arkansas; REAVIS, COLBY - University Of Arkansas; Reba, Michele; Adviento-Borbe, Arlene; PENA, JASQUELIN - University Of California, Davis; Pinson, Shannon

Submitted to: Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 6/21/2021
Publication Date: 6/22/2021
Citation: Runkle, B., Seyfferth, A., Reid, M., Limmer, M., Moreno-Garcia, B., Reavis, C., Reba, M.L., Adviento-Borbe, A.A., Pena, J., Pinson, S.R. 2021. Rice husk soil amendments as a GHG-mitigating piece of the circular rice production system. Meeting Proceedings. 2021.

Interpretive Summary: N/A

Technical Abstract: Much of the world population depends on rice as a staple food and primary source of calories. Rice production, however, enables atmospheric greenhouse gas emissions and often requires high water use. Moreover, it can be a dietary source of toxic metal(loid)s, provoking human health concerns. Since rice is a significant resource consumer and a large part of the global agricultural economy, increasing the sustainability of rice production could have outsized benefits. There are opportunities for more sustainable field production through application of rice husk as a means of silicon (Si) management. Coupled with cultivation in less flooded, less anoxic soil conditions, these practices may be effective to lower climate impacts, manage water usage and counter the accumulation of metal(loid)s. This production system would take advantage of rice husks as an underutilized byproduct of milled rice. The wide availability of rice husks, with ~10% Si, and their physical proximity to production offers opportunity for agronomic reuse through their application to paddy soils as a Si amendment, but this practice is not commonly implemented. Such application could, alongside alternate wetting and drying or furrow irrigation management, help resolve multiple sustainability challenges in rice production: (1) minimize climate impacts of rice production; (2) reduce irrigation water use; (3) limit toxic metal(loid) accumulation in rice; (4) improve nutrient use efficiency; (5) reuse a waste product of rice processing systems; and (6) help close the Si cycle in paddy environments. Since husk currently has generally low-value end-uses or even is viewed as a waste (and whose ash can be carcinogenic), its application on rice fields may represent a relatively achievable instance of bio-circularity. We note that our commentary has the following focus points: Region and system: This analysis is derived in our work in the US mid-south rice production system but is likely relevant in most places where rice is grown. Circularity: We advocate for reuse of rice husk as an on-farm amendment; Mitigation of GHG emissions: Husk amendments will enable reduced water and nutrient use, increased capacity to reduce greenhouse gas emissions (both CH4 and N2O) through increased resilience to drier soil conditions and through reduced N application, respectively. In this presentation, we review how such a shift in rice production practice could operate, identify challenges, opportunities, and synergies to its implementation, and highlight remaining questions. This presentation also suggests how farmers and millers might implement this practice together, and what this shift would look like from a systems or ‘circular economy’ perspective. The purpose is to advocate for a changed rice production method that meets multiple challenges simultaneously, for consideration by community stakeholders, including producers, millers, researchers, extension specialists, supply chain organizations, civil-society partners, and consumers.