Optimizing delayed sowing date decreases methane emissions from paddies and ensures the comprehensive benefits of rice production

Abstract

Adjusting the sowing date presents a cost-effective and advantageous practice to mitigate the adverse effects of climate change on agricultural cultivation. However, its impact on the comprehensive benefits of rice production in terms of methane (CH4) emissions remains uncertain. During the 2019–2021 rice growing season, field studies with different sowing dates were carried out, including a conventional sowing date (CS) and a delayed sowing date of 10 days (DS1) and 20 days (DS2) from the conventional sowing date. CH4 fluxes were monitored using a transparent box-high precision greenhouse gas analyzer (LGR). During the crucial growth stage of rice, the physicochemical properties and enzyme activities of the soils were assessed, while both atmospheric and soil temperatures were recorded. Changes in rice yields were analyzed, and the comprehensive benefits of rice production were calculated. The results demonstrated a significant decrease in the peak of CH4 flux with the delayed sowing date, and the growth stages of rice characterized by high cumulative CH4 emissions were observed to be delayed. Compared to CS, DS1 and DS2 exhibited reductions in cumulative CH4 emissions by 29.98 % and 56.61 %, respectively (three-year average). Atmospheric and soil temperatures showed significant increasing exponential correlations with CH4 fluxes, and temperature sensitivity decreased with the delay of sowing date. The delayed sowing date resulted in more stable changes in soil carbon and nitrogen levels, elevated soil pH, and diminished soil enzyme activity, which could potentially serve as a mechanism for mitigating CH4 flux. DS1 improved the solar radiation and heat utilization efficiency of rice and promoted the growth of panicles and grains, so the yield increased by 20.16 % compared with CS. However, the growth period of DS2 was insufficient for photosynthetic product formation and posed a risk of yield reduction, with an average decrease of 6.46 % over the three-year average. Relative to CS, DS1 effectively reduced cumulative CH4 emissions while ensuring an increase in production, resulting in a 28.90 % increase in comprehensive benefits. Although DS2 achieved greater reductions in cumulative CH4 emissions, the decline in yield resulted in a 7.73 % decrease in comprehensive benefits. In summary, optimizing delayed sowing (delayed sowing for 10 days) is conducive to achieving rice yield and CH4 emission reduction, and this finding provides important and novel insights for eco-efficient rice planting.