The lateral transport of labile organic carbon represents a critical pathway for soil organic carbon (SOC) loss, reducing organic carbon sequestration and increasing the risk of waterbody pollution.  Livestock manure application on croplands serves as a common fertilizer reduction practice to sustain crop yields, enhance SOC sequestration, and reduce water erosion.  However, limited quantitative assessments have examined the effects of livestock manure substitution on labile organic carbon lateral loss and fluxes in long-term experiments.  This study conducted a three-year field investigation on subtropical sloping croplands to assess the impact of livestock manure substitution on dissolved organic carbon (DOC) and particulate organic carbon (POC) loss via surface runoff, interflow and eroded sediments.  There are four treatments: no fertilization (CK); chemical nitrogen fertilizer (SF), 40% nitrogen substitution with pig manure (PMF), and 100% nitrogen substitution from pig manure (PM).  Compared to SF treatment, long-term livestock manure substitution in PMF and PM treatments significantly (P<0.05) reduced annual cumulative surface runoff fluxes by 13.5 and 21.6%, respectively.  Manure applications decreased annual sediment fluxes by 12.9 and 19.1%, respectively.  Soil water stable aggregates for mean weight diameter (MWD) increased significantly by 37.7 and 73.6%.  Annual cumulative POC loss flux via eroded sediment under PMF and PM treatments increased significantly (P<0.05) by 61.1 and 47.9%, respectively.  The labile organic carbon loss fluxes, including DOC and POC losses, under PMF and PM treatments increased significantly (P<0.05) by 11.9 and 31.4%, respectively.  These results demonstrate that while water erosion intensity decreases due to enhanced soil aggregate stability, the risk of labile organic carbon loss increases after long-term livestock manure substitution in subtropical sloping croplands.  Future research should examine labile organic carbon lateral migration under various soil types and slope gradients for livestock manure application in subtropical agricultural ecosystem croplands to better understand extreme rainfall effects.

Cattle carcass traits are economically important in the beef industry.  In the present study, we identified 184 significant genes and 822 alternative genes for 7 carcass traits using genome-wide association studies (GWAS) in 1,566 Huaxi beef cattle.  We then identified 5,860 unique cis-genes and 734 trans-genes in 227 longissimus dorsi muscle (LDM) samples to better understand the genetic regulation of gene expression.  Our integration study of the GWAS and cis-eQTL analysis detected 13 variants regulating 12 identical genes, in which one variant was also detected in fine-mapping analysis.  Moreover, using a transcriptome-wide association study (TWAS), we identified 4 genes (TTC30B, HMGA1, PRKD3 and FXN) that were significantly related to carcass chest depth (CCD), carcass length (CL), carcass weight (CW) and dressing percentage (DP).  This study identified variants and genes that may be useful for understanding the molecular mechanism of carcass traits in beef cattle.

Excessive nitrogen (N) losses from cropland are serious threats to sustainable agricultural and ecological development.  Recently, straw and biochar (BC) have been widely applied in cropland to reduce soil N losses, but the mechanisms by which their physicochemical properties affect soil N cycling and soil N losses remain unclear.  This study investigated the responses of soil N transformation and crop yield on BC and straw applications through incubation and field experiments.  Density function theory (DFT) calculations were performed to determine the different impacts of straw and BC on soil N losses at the molecular scale.  Our results indicated that BC application at a weight percent of 3 (3.0wt %) exhibited superior performance in promoting soil N transformation.  The superior physicochemical properties of BC over straw contributed to enhanced interaction and adsorption energies with NO₃^--N and NH₄⁺-N, which reduced soil N losses by 20.2% from interflow of field experiment compared to straw.  BC application reduced soil N₂O by 45.0% compared to the field with conventional fertilization by modulating the functional genes of microorganisms and weakening the soil denitrification.  Although BC increased soil NH₃ volatilization by improving urease functional genes (ureC, UreB) compared to straw, it also significantly improved N use efficiency in 25.3% of the crops compared to straw.  Thus, in calcareous purple soils, 3.0 wt% BC content provided superior performance in terms of enhanced N cycling, reduced N losses and improved crop yields compared to straw.  In conclusion, these findings provide insights into optimizing cropland BC application and enhancing soil fertility for sustainable agricultural and ecological developments.