Trade-off of greenhouse gas emissions from double-cropped rice due to straw retention and zero tillage practices

CONTEXT

Zero tillage and straw retention have been presented large scale to curb the menace of straw burning and sustaining soil health in rice production systems. At the same time, we know rice cultivation particularly double rice cropping system is an anthropogenic source of atmospheric greenhouse gas (GHGs) emissions, mainly, Methane (CH₄), Nitrous oxide (N₂O), and Carbon dioxide (CO₂). Thus, it is important to know how straw retention and zero tillage affect the GHGs emissions in the rice-rice system.

OBJECTIVE

The study, we made an effort to assess the straw retention/incorporation and zero-tillage (ZT) practices on GHGs emissions, yield, and soil labile carbon pools in rice, to identify sustainable practices that reduce GHG emissions, improve soil health, and at the same time addresses the issue of straw burning.

METHODS

A two-year field study was conducted with four (04) treatments; (i) Immediate incorporation of rice straw after harvesting of previous crop (IIRS); (ii) Zero-tillage (with straw retention) with glyphosate spray (ZT); (iii) Spreading of rice straw over field (SRS); and (iv) Zero-tillage (with straw retention) without glyphosate application (ZT + SR). The GHGs fluxes were measured during both straw decomposition (before rice transplanting) as well as rice growing periods during both wet and dry seasons of the two consecutive years.

RESULTS AND CONCLUSIONS

The average seasonal Methane (CH₄), Nitrous oxide (N₂O), and Carbon dioxide (CO₂) emissions and global warming potential (GWP) were significantly higher in IIRS followed by SRS, ZT, and ZT + SR during straw decomposition as well as rice growing periods. Similarly, the soil labile carbon pools and enzymatic activities were also higher in IIRS as compared to other treatments. Moreover, the increased percentage of SOC from initial to final was higher in IIRS (25.8 %), followed by SRS (23.3 %), ZT (20.7 %), and ZT + SR (17.9 %). However, the crop yield was not significantly influenced by the straw incorporation/retention and tillage practices. So, it is evident there is a trade-off of soil carbon improvement & GHGs emissions in zero tillage (ZT) and straw retention/ incorporation practices. Straw retention/incorporation in soil on one hand increased carbon storage but at the same time also enhanced GHGs emissions. Zero tillage (with straw retention) without glyphosate spray could be recommended for sustainable straw management.

SIGNIFICANCE

The study identifies zero-tillage with straw retention without glyphosate spray (ZT + SR) for sustainable straw management, which increases the carbon build-up and decreases the GHGs emissions while addressing the issue of straw burning.