Effects of different fertilization practices on anammox activity, abundance, and community compositions in a paddy soil

Abstract

The return of crop residue and green manure into agricultural soil is known to be important agricultural management strategies, yet how they affect the anammox process remains poorly characterized. A field experiment containing four treatments: chemical fertilizer (F), F plus rice straw (FS), FS plus green manure (FSM), FSM with integrated management (FSMM), was performed to examine the effects of incorporation of rice straw and green manure residues on anammox. The results showed that the anammox activities in FS and FSM treatments (0.65 and 0.80 nmol N g -1 soil h -1 , respectively) were significantly lower than those in F and FSMM treatments (1.60 and 1.28 nmol N g -1 soil h -1 , respectively). Anammox contributed 4.07%-4.95% of total N loss in soil incorporated with residues, lower than soil treated with chemical fertilizer only (9.13%), the remaining being due to denitrification. However, the abundance of the hzsB gene (the hydrazine synthase β-subunit gene) in FS and FSM treatments (1.13 Â 10 6 and 1.18 Â 10 6 copies g -1 soil) were significantly higher than soil using chemical fertilizer only (7.49 Â 10 5 copies g -1 soil) while showed no significant difference with FSMM treatment (8.81 Â 10 5 copies g -1 soil). Illumina sequencing indicated that Brocadia was the dominant anammox genus, following by Scalindua and Kuenenia. Anammox bacterial diversity was altered after 4-year incorporation of rice straw and green manure, as shown by α-diversity indices. We concluded that rice straw and green manure incorporated with mineral fertilizer reduce N removal from paddy soil in terms of anammox in spite of stimulating anammox bacterial growth.

Rice planting acceleration of the activation and loss of soil iron in the red soil region of southern China

“…The soil parent materials of this zone differ greatly and land use type are diverse. In particular, paddy fields are heavily influenced by human activities with a long history (Sun et al, 2022). The migration and loss characteristics of iron in agricultural and woodland soils in the southern red soil region of China, under the influence of both natural and significant human activities, are not yet clear.…”