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Quantitative information on cropland phosphorus (P) flows at the township scale is critical for developing sustainable P management measures under the smallholder farming system. This study addressed changes in cropland soil surface P budgets (i.e., net of P inputs and crop outputs), use efficiencies (i.e., the ratio between crop P uptake and total P input) and legacy P pools across 21 townships in the Yongan watershed of eastern China in 1980-2010. For the entire watershed, total P input (>98% from synthetic fertilizer and farmyard manure), crop uptake and budgets per cropland area increased from 50.4, 17.3 and 33.1 kg P ha À1 yr À1 in 1980 to 74.6, 20.5 and 55.1 kg P ha À1 yr À1 in 1995, and then sharply declined to 39.6, 11.4 and 28.2 kg P ha À1 yr À1 in 2010, respectively. Estimated P use efficiency decreased from 34% in 1980 to 26% in 1999 before slightly increasing to 28% in 2010. Although the 21 townships had similar temporal variations over the 1980-2010 period, P budgets and use efficiency showed 2-3-fold spatial variability among townships within a given year. Spatio-temporal variations in the P budget and use efficiency were mainly related to changes in P fertilization rates and patterns (i.e., ratio of applied synthetic fertilizer P and farmyard manure P) and cropland types. The 20 townships having soil data had 87-720% and 113-395% increases of Olsen-P and total P contents in the upper 20 cm of cropland soils between 1984 and 2009, respectively. Increased soil TP level between 1984 and 2009 suggested that more than 53-79% of the cumulative P budget accumulated as legacy P pools in cropland soils. Based on regression analyses, legacy soil P contribution to annual crop P uptake was estimated to increase from 0.47 kg P ha À1 yr À1 (3%) in 1980 to 3.45 kg P ha À1 yr À1 (31%) in 2010, with 52-80% from synthetic fertilizer and 2-46% from farmyard manure. Improved utilization of soil legacy P pools for crop production and increasing P use efficiency are necessary to minimize P inputs and reduce nonpoint source P pollution load. The high spatial heterogeneity in P budgets and use efficiencies across townships, as well as considerable legacy soil P pools after long-term over-application, should be considered in developing P management strategies under smallholder farm systems.

Legacy nitrogen (N) is recognized as a primary cause for the apparent failure of watershed N management strategies to achieve desired water quality goals. The ELEMeNT-N (Exploration of Long‐Term Nutrient Trajectories for Nitrogen) model, a parsimonious and process-based model, has the potential to effectively distinguish biogeochemical and hydrological legacy effects. However, ELEMeNT-N is limited in its ability to address long-term legacy N dynamics as it ignores temporal changes in soil organic N (SON) mineralization rates. This work represents the first use and modification of ELEMeNT-N to quantify legacy effects and capture spatial heterogeneity of legacy N accumulation in China. An exponential function based on mean annual temperature was employed to estimate yearly changes in SON mineralization rate. Based on a 31-year water quality record (1980-2010), the modified model achieved higher efficiency metrics for riverine N flux in the Yongan watershed in eastern China than the original model (Nash-Sutcliff coefficient: 0.87 vs. 0.72 and R2: 0.80 vs. 0.71). The modified ELEMeNT-N results suggested that the riverine N flux mainly originated from the legacy N pool (88.2%). The mean overall N lag time was 11.9 years (95% CIs: 8.3-21.3), of which biogeochemical lag time was 9.7 years (6.3-18.4) and hydrological lag time was 2.2 years (2.0-3.0). Legacy N accumulation showed considerable spatial heterogeneity, with 219-239 kg N ha-1 accumulated in soil and 143-188 kg N ha-1 accumulated in groundwater. The ELEMeNT-N model was an effective tool for addressing legacy N dynamics, and the modified form proposed here enhanced its ability to capture SON mineralization dynamics, thereby providing managers with critical information to optimize watershed N pollution control strategies.

To investigate the carrying situation of N. gonorrhoeae genetic island (GGI), and to understand the existence of GGI of different multilocus sequence types (MLST), so as to provide evidence for epidemiology. Methods: From January 2018 to December 2020, a total of 37 clinical isolates of N. gonorrhoeae were collected. Resistance to tetracycline, β-lactam, and azithromycin were measured. Genes in GGI (atlA, traG, and traH) were amplified via polymerase chain reaction (PCR). All clinical isolates were subjected to N. gonorrhoeae MLST. Results:The GGI of N. gonorrhoeae were widespread, and the positive detection rates of atlA, traG and traH were all 81.08% (30/37). In this study, atlA, traG and traH were always detected positive together. No significant difference in the positive rate of the GGI between the azithromycin-sensitive and the resistance groups or between the β-lactam positive and negative groups (P > 0.05) was found; however, there was a significant difference between the high-level tetracycline-resistant group and the non-high-level resistant group (P < 0.05), with the carrier rates being 60.00% and 94.45%, respectively. Among the 37 isolates studied, 12 distinct MLST were determined, while MLST ST8123 occurred most frequently, accounting for 18.91% (7/37), followed by ST1928, ST7367 and ST7822, all 13.51% (5/37). Conclusion: N. gonorrhoeae typed as ST1928, ST1901, ST1588 and ST7822, the GGI were all positive. These four types are more likely to become highly virulent strains.