Core Ideas We used CT‐derived parameters to explain solute, water, and air transport at field scale. CTmatrix was found to be the best parameter to explain solute transport. Limiting macroporosity gave the highest correlations with water and air transport. Combining macroporosity and CTmatrix improved the relationships of water and air flow. The characterization of soil pore space geometry is important for explaining fluxes of air, water, and solutes through soil and understanding soil hydrogeochemical functions. X‐ray computed tomography (CT) can be applied for this characterization, and in this study CT‐derived parameters were used to explain water, air, and solute transport through soil. Forty‐five soil columns (20 by 20 cm) were collected from an agricultural field in Estrup, Denmark, and subsequently scanned using a medical CT scanner. Nonreactive tracer leaching experiments were performed in the laboratory along with measurements of air permeability (Ka) and saturated hydraulic conductivity (Ksat). The CT number of the matrix (CTmatrix), which represents the moist bulk density of the soil matrix, was obtained from the CT scans as the average CT number of the voxels in the grayscale image excluding macropores and stones. The CTmatrix showed the best relationships with the solute transport characteristics, especially the time by which 5% of the applied mass of tritium was leached, known as the 5% arrival time (t0.05). The CT‐derived macroporosity (pores >1.2 mm) was correlated with Ka and log10(Ksat). The correlation improved when the limiting macroporosity (the minimum macroporosity for every 0.6‐mm layer along the soil column) was used, suggesting that soil layers with the narrowest macropore section restricted the flow through the whole soil column. Water, air, and solute transport were related with the CT‐derived parameters by using a best subsets regression analysis. The regression coefficients improved using CTmatrix, limiting macroporosity, and genus density, while the best model for t0.05 used CTmatrix only. The scanning resolution and the time for soil structure development after mechanical activities could be factors that increased the uncertainty of the relationships. Nevertheless, the results confirmed the potential of X‐ray CT visualization techniques for estimating fluxes through soil at the field scale.

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Abstract:Modern agriculture has been one of the causes for biodiversity degradation. Conservation of the remaining biodiversity is of utmost importance and novel approaches and concepts should be tested to achieve this end. As a recent development in microbiology, fungal surface-attached bacterial communities or fungal-bacterial biofilms (FBBs) are being studied for various biotechnological applications with consequences in ecosystem functioning and biodiversity. The present study was conducted to investigate the effect of the introduced FBBs on restoration of reduced biodiversity in the soil of a degraded tea land. The soil was treated with a developed biofilm, its monocultures, the nutrient solution used for culturing the microbes, and sterilised distilled water in a pot experiment. After three months, the soils were evaluated for plant and culturable microbial species richness, microfaunal count, nitrogenase activity, and selected soil parameters. It was observed that the biofilm application resulted in a significantly higher plant species richness than the respective monocultures (p < 0.05). Further, culturable bacterial and fungal species richnesses, soil nitrogenase activity, organic carbon, and available ammonium and nitrate increased significantly with the biofilm application, compared with the application of the nutrient solution and distilled water (p < 0.05). Results of the present study indicated that inoculation of the developed microbial biofilms influences microbial and plant diversity and soil quality parameters positively. These observations indicate that the microbial biofilms developed in this study may have the potential to be developed as a novel biotechnological tool to mitigate biodiversity loss in agroecosystems and perhaps in natural ecosystems.