- BB
Authors: Singh, G.; Advisor: -; Participants: Kaur, G.; Williard, K.; Schoonover, J.; Kang, J. (2018) - A number of contaminants including agrochemicals (fertilizers, pesticides), heavy metals, trace elements, and pathogenic microbes along with pharmaceuticals and hormones used in animal production move through the soil and are responsible for degradation of groundwater quality. Therefore, it is essential to sample soil solution for better understanding of movement and environmental fate of various contaminants in soils. We review different soil solution extraction samplers. The soil solution samplers discussed here are: drainage lysimeter or soil column, pan lysimeter, resin bags or membranes, wick lysimeters, suction cup, and suction plate. We have reviewed 304 journal articles representing a wide array of scientific disciplines. A brief history of soil solution monitoring and termi...
|
- BB
Authors: Wang, Z.; Advisor: -; Participants: Luo, C.; Sauer, T.J.; Helmers, M.J.; Horton, R. (2018) - Crop canopy CO2 exchange rate (CER) includes crop photosynthesis and soil/plant respiration. A portable canopy chamber is effective in determining crop CER values at a relatively small spatial (m2) scale. The objectives of this study were to use a canopy chamber to measure CO2 fluxes in corn (Zea mays L.) and soybean [Glycine max (L.) Merr.]. Chamber measurements were performed for 18 and 15 d in 2013 and 2014, respectively. The canopy chamber measures instantaneous CER fluxes, and daily and daytime cumulative CO2 values were calculated from the instantaneous CER. The chamber CER results were compared with nearby eddy covariance (EC) flux tower measurements at a variety of time scales, i.e., instantaneous, daily, and daytime cumulative (multiple months). The daily and daytime cumula...
|
- BB
Authors: Zhu, W.; Advisor: -; Participants: Li, H.; Qu, H.; Wang, Y.; Misselbrook, T.; Li, X.; Jiang, R. (2018) - The soil water storage (SWS) decreased significantly during the early stage of the maize growing season, especially in 2014. The root depth and crop height were 20 cm deeper and 100 cm higher, respectively, in 2014 than in 2013 at the early stage. These results suggest that in the early stage of the maize growing season, pre‐seeding SWS can alleviate crop water stress effectively via deep roots. Model simulation showed that the plow pan layer (at a depth of 20–40 cm), with high soil bulk density and a lower soil water retention curve, significantly reduced infiltration. High evapotranspiration and low precipitation result in a temporary dry layer during the early stage, highlighting the plow pan as the sensitive layer for water stress during the drought period. Effective management ...
|
- BB
Authors: Berezniak, A.; Advisor: -; Participants: Ben-Gal, A.; Mishael, Y.; Nachshon, U. (2018) - Drip irrigation is a useful method for the application of low‐quality water because it does not wet the foliage and limits the spread of contaminants. Nevertheless, when using water containing high levels of dissolved salts, drip irrigation may be insufficient for leaching and can lead to soil salinization. A new conceptual model was tested experimentally and numerically to examine if manipulation of the distribution of soils with different textures could promote the removal of salts from the root zone and increase leaching efficiency. The manipulated root zone consisted of a volume of coarse soil, located under a drip irrigation emitter, surrounded by finer texture soil. We hypothesized that the differences in hydraulic properties between the two soils and the capillary barrier dev...
|
- BB
Authors: Cai, C.; Advisor: -; Participants: Vanderborght, J.; Couvreur, V.; Mboh, C.M.; Vereecken, H. (2018) - These models were implemented in HYDRUS‐1D, and soil hydraulic parameters were optimized by inverse modeling using soil water content and potential measurements and observations of root distributions of winter wheat (Triticum aestivum L.) in horizontally installed rhizotubes. Soil moisture was equally well predicted by the three models, and the soil hydraulic parameters optimized by the models with compensation were comparable. The obtained RWU parameters of the Feddes–Jarvis model were consistent with data reported in the literature, although the pressure heads h3l and h3h for lower and higher transpirations rates, respectively, could not be uniquely identified. Response surfaces of the objective function showed that the root‐related parameters of the Couvreur model could be identi...
|
- BB
Authors: Bean, E.Z.; Advisor: -; Participants: Huffaker, R.G.; Migliaccio, K.W. (2018) - We evaluated competing approaches for automated soil water cycles analysis that use widely available R packages based on pattern recognition and machine learning (findpeaks [R‐FP], symbolic aggregate approximation [R‐SAX], and density histogram [R‐DH]), and a MATLAB code based on soil water dynamic principles (SWDP). These approaches were applied to three SMS datasets. Our empirical results showed superiority of R‐SAX for identifying valid soil water cycles, probably due to benefiting from training sets to calibrate to correct cycles. Two other approaches (SWDP and R‐FP) provided similar results without need of training sets or preprocessing data. Three approaches for estimating field capacity were applied to valid cycles, R‐FP, regression of exponential decay (SWDP‐R), and estimate...
|
- BB
Authors: Smith, E.A.; Advisor: -; Participants: Capel, P.D. (2018) - A specific conductance end‐member mixing analysis (SC‐EMMA) was used to determine the volume of water that infiltrated through preferential flow pathways. The SC‐EMMA was used for 20 of the 25 paired rainfall–SC events; of the 20 classified events, the maximum preferential flow ranged from 11 to 75% of the total subsurface drain flow, with a mean maximum preferential flow of 31%. Overall, SC‐EMMA illustrated that a significant portion of the subsurface drain discharge can be attributed to preferential flow, mainly through macropores or other largely open preferential flow pathways. The other primary mechanism, antecedent moisture conditions shifts, could only be shown for four of the 25 classified events. Specific conductance as a tracer of preferential flow was shown to be an effec...
|
- BB
Authors: Nocco, M.A.; Advisor: -; Participants: Kraft, G.J.; Loheide II, S.P.; Kucharik, C.J. (2018) - We found that interannual climate variability, subtle differences in soil texture, and cropping system type drove potential recharge to varying degrees during the summer and fall seasons. Relatively finer soil texture was positively correlated to point estimates of potential recharge. This correlation was the strongest following large precipitation events. June to November cumulative potential recharge for 2013 to 2016 averaged 71 ± 235 mm across all lysimeters. Our findings suggest that aquifer depletion will be an episodic process that leaves surface waters most vulnerable to pumping and recharge impacts during and following drier years in the WCS. Differences among cropping systems were most pronounced under average precipitation conditions, which facilitated potential groundwate...
|
