Winter cover crops hold potential to capture excess NO3− and reduce leaching by recycling nutrients. The objective of this study was to compare winter NO3‐N leaching losses under winter‐fallow and a winter cereal rye (Secale cereale L.) cover crop following the harvest of sweet corn (Zea mays L.) or broccoli (Brassica oleracea var. italica Plenck). Leachate was sampled with passive capillary wick samplers that apply a suction of 0 to 5 kPa to the soil‐pore water and intercept leachate in a pan of known area. Without disturbing the over‐laying soil profile, 32 samplers (0.26 m2) were installed at a depth of 1.2 m in a Willamette loam (fine‐silty mixed mesic Pachic Ultic Argixeroll). The randomized complete‐block split plot design of this cover crop‐crop rotation study (initiated in 1989) has cropping system (winter fallow vs. winter cereal rye) as main plots and three N application rates, ranging from 0 to 280 kg N ha−1 yr−1, as subplots. At the recommended N rate for the summer crops, NO3 leaching losses were 48 kg N ha−1 under sweet corn‐winter‐fallow for winter 1992–1993, 55 kg N ha−1 under broccoli‐winter‐fallow for winter 1993–1994, and 103 kg N ha−1 under sweet corn‐winter‐fallow for winter 1994–1995, which were reduced to 32, 21, and 69 kg N ha−1, respectively, under winter cereal rye. For the first two winters, most of the variation (61%) in NO3− leaching was explained by N rate (29%), cereal rye N uptake (17%), and volume of leachate (15%). Seasonal, flow‐weighted concentrations at the recommended N rate were 13.4 mg N L−1 under sweet corn‐winter‐fallow (1992–1993), 21.9 mg N L−1 under broccoli‐winter‐fallow, and 17.8 mg N L−1 under sweet corn‐winter‐fallow (1994–1995), which were reduced by 39, 58, and 22%, respectively, under winter cereal rye.

Soil solution samplers have certain inadequacies that limit their range of possible applications. Passive capillary samplers (PCAPS), which apply suction to the soil pore water via a hanging water column in a fiberglass wick, have shown promising results in preliminary experiments in regard to collection efficiency of water and Br tracers. The objectives of this study were to evaluate PCAPS with respect to (i) effect of installation procedure and operational characteristics; and (ii) ability to estimate the soil‐water and solute flux. We installed 32 PCAPS and 32 ceramic suction cup samplers at a depth of 1.2 m in an undisturbed silt loam soil. For the first year, water flux, NO3‐N and Br concentrations in the part of the PCAPS closest (0.3 m) to the refilled trench were 15, 14, and 34% less, respectively, than in the part farthest (0.9 m) away from the refilled trench. This was attributed to installation procedure, since the bias ceased for the second year. Soil‐water flux measurements of PCAPS underestimated those determined by a water balance by 20 to 34%. Some of the discrepancy is thought to be due to the lack of accounting for runoff, which was observed but not quantified. The recovery of a Br tracer was low with an average of 29%, ranging from 5 to 77%, which was attributed to lateral water movement due to prominent lateral stratification. To estimate the mean Br concentration with a 30% bound at the 0.05 confidence level on this 1‐ha field site, 25 PCAPS and 37 suction cup samplers are necessary. Sampling a more evenly distributed solute such as residual fertilizer NO3 requires only eight PCAPS for this level of confidence.

An accurate assessment of leaching losses in the vadose zone requires measurement of both solute and water flux to compute flux concentrations (CF). Leachate collected at a depth of 1.2 m in 32 passive capillary samplers (PCAPS), which sample soil‐pore water continuously at tensions of 0–50 cm H2O was compared to that collected in 32 suction cup samplers operated under a falling head vacuum of 530‐cm H2O over a 2‐year period. There was evidence that PCAPS collected CF and suction cup samplers collected resident concentrations (CR) as shown by the earlier breakthrough of a bromide tracer in the PCAPS as compared to the suction cup samplers. CR was up to 100% lower than CF during the rising branch of Br tracer breakthrough and up to 78% greater during the declining branch of breakthrough. Br content and water flux into PCAPS were correlated with correlation coefficients changing from positive to negative values with the advancement of the tracer breakthrough peak through the profile indicating the declining importance of preferential flow on Br transport. CR and CF differed significantly (P < 0.05) for 35% of the sampling events for NO3, but seasonal means were mostly insignificantly different for this regularly applied and therefore more uniformly distributed anion. The early breakthrough of Rhodamine WT and Brilliant Blue FCF, which was applied with the Br, was very low with 0.15% and 0.08% of the initial concentration C0, respectively, with CR differing from CF by up to −100%. For all tracers, mass leached using CR is therefore prone to bias for short‐term (<0.6 pore volumes) monitoring.

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Developers are usually unaware of the impact of code changes to the performance of software systems. Although developers can analyze the performance of a system by executing, for instance, a performance test to compare the performance of two consecutive versions of the system, changing from a programming task to a testing task would disrupt the development flow. In this paper, we propose the use of a city visualization that dynamically provides developers with a pervasive view of the continuous performance of a system. We use an immersive augmented reality device (Microsoft HoloLens) to display our visualization and extend the integrated development environment on a computer screen to use the physical space. We report on technical details of the design and implementation of our visualization tool, and discuss early feedback that we collected of its usability. Our investigation explores a new visual metaphor to support the exploration and analysis of possibly very large and multidimensional performance data. Our initial result indicates that the city metaphor can be adequate to analyze dynamic performance data on a large and non-trivial software system.