Effects of mild alternate wetting and drying irrigation and rice straw application on N₂O emissions in rice cultivation

Abstract

Abstract. The shortage of water resources and the decline in soil organic matter (SOM) are critical limiting factors affecting the improvement in rice productivity, while alternate wetting and drying (AWD) irrigation and recycling application of rice straw (S) are considered favorable mitigation measures. However, the impact of such measures on rice yield and greenhouse gas (GHG) emissions, especially nitrous oxide (N2O) emissions, needs to be further clarified to ensure that agronomic practices save water, conserve soil, and reduce GHG emissions. Therefore, we explored the effects of mild AWD irrigation combined with on-site rice straw recycling on N2O emissions and rice yield through rice pot experiments. This experiment included 2 irrigation methods (continuous flooding (CF) irrigation and mild AWD irrigation), 2 nitrogen (N) application levels (0 and 225 kg N ha−1) and 2 rice straw return levels (0 and 9000 kg ha−1), for a total of 10 treatments, and each treatment had 3 replicates. The 15N-urea and 15N-S were added to the soil. The results showed that N2O emissions were primarily affected by urea application and irrigation methods, with urea application being most important. Compared with CF irrigation, mild AWD irrigation increased cumulative N2O emissions, with an average increase of 28.8 %. In addition, adding rice straw to mild AWD irrigation further stimulated N2O emissions by 18.1 %. Under the condition of urea application, compared with CF irrigation, mild AWD irrigation increased the yield-scaled N2O emissions by 17.9 %, and the addition of rice straw further promoted the yield-scaled N2O emissions under mild AWD irrigation by 17.4 % but reduced the global warming potential (GWP) (methane (CH4) + N2O) by 62.9 %. Under the condition of urea application, compared with CF irrigation, mild AWD irrigation reduced the uptake of soil-derived N and aboveground biomass of rice but did not reduce rice yield. Therefore, mild AWD irrigation combined with rice straw return may be a promising agronomic method to maintain rice yield, reduce GHGs, and protect or improve soil fertility.

Interaction between water, crop residue and fertilization management on the source-differentiated nitrogen uptake by rice

“…With respect to CF, the adoption of AWD cycles after tillering was shown to result in a lower plant growth during the early vegetative stages, particularly for root development, in line with previous findings (Suriyagoda et al 2014;Weerarathne et al 2015;Zhou et al 2020;Wu et al 2022). Several authors have however observed a positive plant growth response under AWD, with an increase in root length and dry matter accumulation (Kato and Okami 2010;Thakur et al 2011;Hazra and Chandra 2016;Abid et al 2022).…”

“…Water management did not only affect the total plant N uptake but also the source partitioning of the assimilated N. Under both water managements, SDN and FDN contributed most to plant N at 60 DAS (46-64 and 34-49%, respectively), while StDN only contributed as a minimal fraction (3% for both CF and AWD), in line with the findings of Wu et al (2022) who also reported a similar partitioning of rice N uptake under AWD. Our results agree with those reported by Chen et al (2016) who reported that 34-42% of rice plant N was derived from fertilizer-N and 58-66% from soil N. Similarly, Hashim et al (2015) reported FDN values for rice ranging from 20 to 35%.…”

“…Unlike FDN, the fraction of SDN was greatly affected by water management, showing a significantly lower contribution to plant N nutrition under AWD (on average 14% less) with respect to permanent flooding irrigation (Fig. 5), in line with the findings of Wu et al (2022). This is in contrast with the faster mineralization of soil organic N during the more frequent oxic soil conditions we hypothesized for AWD (Hypothesis 1).…”

Effects of corn stalks returning on soil microbial carbon use efficiency and corn yield in semi-arid cropland

“…Corn stalks returning was considered to improve the physicochemical properties of soil (Chan et al 2002;Wu et al 2021). Wu et al (2022) also showed that straw returning could increase soil NO3 --N. The increase in NO3 --N, DOC, and DON may be due to the stimulation of extracellular enzyme activity by the addition of corn stalks (Chen et al 2014), and the decomposition of corn stalks releases macronutrients and changes nutrient availability (Devevre and Horwath 2000). Therefore, corn stalks returning may be beneficial to improving soil fertility in semi-arid cropland, but the effect of improving SOM needs longterm monitoring.…”