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A field experiment was carried out to evaluate the effect of organic amendments on soil organic carbon, total nitrogen, bulk density, aggregate stability, field capacity and plant available water in a representative Chinese Mollisol. Four treatments were as follows: no fertilization (CK), application of inorganic fertilizer (NPK), combined application of inorganic fertilizer with maize straw (NPK+S) and addition of biochar with inorganic fertilizer (NPK+B). Our results showed that after three consecutive years of application, the values of soil bulk density were significantly lower in both organic amendment-treated plots than in unamended (CK and NPK) plots. Compared with NPK, NPK+B more effectively increased the contents of soil organic carbon, improved the relative proportion of soil macro-aggregates and mean weight diameter, and enhanced field capacity as well as plant available water. Organic amendments had no obvious effect on soil C/N ratio or wilting coefficient. The results of linear regression indicated that the improvement in soil water retention could be attributed to the increases in soil organic carbon and aggregate stability.

. Taken together, the findings reported here suggest that both the river N 2 O concentrations and emissions would increase in response to rising anthropogenic nitrogen loads. Our study showed that the mean emission factor based on the ratio of the total N 2 O flux to NO 3 À flux is four times greater than the value of 0.0025 obtained with the methodology recommended by the Intergovernmental Panel on Climate Change. Thus, our findings reflect the open river channel rapid exchange of gases with the atmosphere.

An important unsolved challenge in tissue engineering has been the inability to replicate the geometry and function of vascular networks and blood vessels. Here, we engineer a user-defined 3D microfluidic vascular channel using 3D printing-enabled hydrogel casting. First, a hollow L-shaped channel is developed using a template casting process. In this process, murine 10T1/2 cells are encapsulated within gelatin methacrylate (GelMA) hydrogel using UV photocrosslinking, and upon removal of the template results in a hollow channel within GelMA. Second, human umbilical vein endothelial cells (HUVECs) were cultured within the channel and immunostaining was used to visualize endothelial monolayers. Third, diffusion/permeability studies on endothelialized channels were carried out to demonstrate the barrier function of HUVEC monolayer. Taken together, we develop a facile, cytocompatible and rapid approach to engineer a user-defined multicellular vascular chip that could be potentially useful in developing new vascular model systems.

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