Symbiotic fungal endophyte Phomopsis liquidambari-rice system promotes nitrogen transformation by influencing below-ground straw decomposition in paddy soil

Abstract

Aims: To explore if and how symbiotic Phomopsis liquidambari-rice system influences below-ground straw decomposition and then nitrogen(N) transformation in response to environmental N levels.

Methods and results: Litter bag experiments were utilized to trace the decay process during rice growth phases (seedling (T1), tillering (T2), heading (T3) and maturing (T4) stage), with (E+) and without endophyte (E-), under low (LN), medium (MN) and high nitrogen (HN) supply. Litter, soil and plant samples were collected to evaluate the decay process, N transformations, plant quality and relative abundance of soil ammonia-oxidizing archaea (AOA), ammonia-oxidizing bacteria (AOB) and P. liquidambari. The results showed that straw decomposition increased by 19·76% (LN, T2 stage), 14·05% (MN, T3 stage) and 16·88% (MN, T4 stage) in E+ pots when compared with E- pots. Further analysis revealed that no significant endophyte × N interaction was found for straw decay rate and that the decay rate was reduced by a higher N supply (LN, 37·16 ± 0·65%; MN, 32·27 ± 1·72%; HN, 29·44 ± 1·22%) at the T1 stage, whereas straw decay rate and N release increased by 9·38 and 11·16%, respectively, mainly by endophyte colonization at the T4 stage. The abundance of AOA and AOB were altered, corresponding with the decay rate. Soil mineral N, straw mineral N and plant quality were shown to increase in E+ pots, depending on environmental N conditions and growth phase. The yield increased by 2·98% for E+ plants under MN level.

Conclusions: Symbiotic P. liquidambari-rice system promoted below-ground straw decomposition and N transformation, depending on environmental N levels and plant growth phase.

Significance and impact of the study: This study provides evidence that fungal endophyte-plant systems are able to promote N transformation by increasing straw decomposition. A reasonable combination of N inputs could enhance its advantage in agriculture ecosystems.

Keywords: ammonia-oxidizing microbes; fungal endophyte; nitrogen transformation; rice straw decomposition; symbiotic system.