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Although widely studied in grassland and forest ecosystems, dissolved organic nitrogen (DON), an important form of nitrogen (N) lost through leaching, has received little attention in cropland ecosystem research. A global literature review and partial least squares path modeling (PLS--PM) were adopted to assess the quantity and composition of N leaching loss under different cropping systems, soil types, and management practices, as well as to identify the major factors controlling DON leaching. Annual total dissolved nitrogen (TDN, organic + inorganic N) leaching under different cropping systems ranged from 4.0 to 383.2 kg N [ha.sup.-1] Vegetable and rice production systems showed the greatest and least TDN leaching, respectively. Across different cropping systems, DON accounted for 4.7%-34.9% of TDN in leachate. The N[H.sup.+.sub.4]-N form of N leaching is negligible in most upland cropping systems ( Key words: nitrogen leaching, dissolved organic nitrogen, cropping system, cropland ecosystem. Bien que largement etudie dans les ecosystemes des prairieset des forets, l'azote organique dissous (AOD), une forme importante d'azote perdu par lessivage, a recu peu d'attention dans la recherche sur les ecosystemes des terres cultivees. Une analyse documentaire generale et une modelisation par PLS--PM ont ete adoptees pour evaluer la quantite et la composition des pertes par lessivage de l'azote selon differents systemes de culture, types de sol et pratiques de gestion, ainsi que pour identifier les principaux facteurs controlant le lessivage de l'AOD. Le lessivage annuel de l'azote dissous total (ADT, N organique + inorganique) sous differents systemes de culture variait de 4,0 a 383,2 kg N [ha.sup.-1]. Les systemes de production de legumes et de riz presentaient respectivement le lessivage le plus important et le moins important de l'ADT. Dans les differents systemes de culture, l'AOD representait entre 4,7 % et 34,9 % de l'ATD du lixiviat. La forme N[H.sup.+.sub.4]-N du lessivage d'azote est negligeable dans la plupart des systemesde culture de montagne ( Mots-cles : lessivage de l'azote, azote organique dissous, systeme de culture, ecosysteme des terres cultivees., 1. Introduction Among the most important elements for plant growth, nitrogen (N) is also an essential participant in the global ecosystem's organic matter cycle (Gruber and Galloway 2008). Contributing over [...]

The legume species Astragalus sinicus (Chinese milk vetch [CMV]) has been widely cultivated for centuries in southern China as one of the most important green manures/cover crops for improving rice productivity and preventing soil degeneration. In this study, we generated the first chromosome-scale reference genome of CMV by combining PacBio and Illumina sequencing with high-throughput chromatin conformation capture (Hi-C) technology. The CMV genome was 595.52 Mb in length, with a contig N50 size of 1.50 Mb. Long terminal repeats (LTRs) had been amplified and contributed to genome size expansion in CMV. CMV has undergone two whole-genome duplication (WGD) events, and the genes retained after the WGD shared by Papilionoideae species shaped the rhizobial symbiosis and the hormonal regulation of nodulation. The chalcone synthase (CHS) gene family was expanded and was expressed primarily in the roots of CMV. Intriguingly, we found that resistance genes were more highly expressed in roots than in nodules of legume species, suggesting that their expression may be increased to bolster plant immunity in roots to cope with pathogen infection in legumes. Our work sheds light on the genetic basis of nodulation and symbiosis in CMV and provides a benchmark for accelerating genetic research and molecular breeding in the future., (© 2022 The Authors.)