Soil property changes after four decades of wastewater irrigation: A landscape perspective

Department of Crop and Soil Sciences, 116 ASI Building, The Pennsylvania State University, University Park, PA 16802, United States
CATENA 01/2008; DOI: 10.1016/j.catena.2007.09.002

ABSTRACT For over 40 years, The Pennsylvania State University (PSU) has irrigated its wastewater onto both cropped and forested lands. Despite local weather conditions, approximately 50 mm/week of wastewater have been spray-irrigated onto the land since 1962. This irrigation, combined with the natural precipitation, amounts to approximately 3550 mm of water per year. The objective of this study was to investigate the morphological and functional changes in soils of this area as a result of this significantly-increased water load. The research area has a karst geology and is dominated by rolling hills with many small depressions that act as sinks for water and sediments. Together with six soil trenches, 47 soil cores were taken across a 6.5-ha field. Previous studies conducted at this site provided a reference for interpreting the changes in soil properties over time. Soil morphological properties, including structure, horizonation, and redoximorphic features, were evaluated from the soil cores and in situ soil pits. In addition, soil functional parameters, including saturated hydraulic conductivity (Ksat), bulk density, organic matter content, and soil pH, were evaluated to determine the soil functional changes. Results indicate that the soils have experienced periods of local saturation and soil transport, which are reflected by the distribution of redoximorphic features and A-horizon thickness across the study area. Sample locations were grouped into three landscape positions (summit, midslope, and depression) that exhibited similar soil properties. The depth of the A-horizon was significantly greater in the depressions, while the midslope position had the highest manganese oxide coating percentage, and the summit position had the highest bulk density. This reflects the likely hydrologic path from the summit to the depression. The depression areas had the highest mean surface Ksat (10.2 cm/h), while the summit areas had the lowest mean surface Ksat (1.2 cm/h). Both organic matter content and soil pH have increased considerably since 1971. Overall, although soil properties have changed through the decades of irrigation, the wastewater spray irrigation system remains functional in this area and the soils are still performing reasonably well; however, some concerns about reduced soil functionality need to be addressed from a landscape perspective in order to sustain this system.

  • [Show abstract] [Hide abstract]
    ABSTRACT: Twelve soil profiles and 62 soil cores were described from two neighboring landscapes in the northwest of Iran to understand whether long-term wastewater irrigation has caused variations in morphological, physicochemical, and DTPA-heavy metals contents in soils. Along a gradual slope, different positions reflected heterogeneous response to flooding wastewater irrigation. Upper slope and mainly midslope were subject to gradual soil loss as characterized by thin Ap-horizons and shallow soil depth, whereas periodic cycles of soil accumulation and sediment along with local reducing condition were highlighted in lower slope. Compared to different positions of control land, wastewater irrigation increased significantly (P ≤ 0.05) soil fertility attributes (N, P, K, and organic matter) along with electrical conductivity. Significant correlations were observed between soil fine particles fraction and available P and also with available K, indicating that spatial distribution pattern of these elements is mainly dependent on distribution of the <0.002 mm fractions along the landscape as it is affected by wastewater irrigation. Midslope position was found to be more degraded compared to the other position regarding soil loss and available nutrients (N, P, and K) as a result of the processes of soil redistribution and soil transport in wastewater irrigation system. Mean concentrations of DTPA-extractable Zn, Cu, Cd, and Pb in the different geomorphological positions were 3.8–7.8, 2.5–3, 3–4, and 1.7–3.5 times greater, respectively, when compared to the adjacent control soil. With the exception of lower slope position, which indicated a remarkable increasing pattern of smectite in response to wastewater irrigation and unfavorable drainage condition, the relative abundances of clay minerals in view of the peak position and intensity followed almost the same pattern in both wastewater-irrigated and control landscape.
    Environmental earth sciences 67(6). · 1.45 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: [1] Advances in nitrogen (N) saturation and retention theories have focused on soil organic matter (SOM) biogeochemistry in the absence of dynamic soil hydrology. Here we exploit two soil types with contrasting textures that span a hillslope gradient to test hypotheses that suggest N saturation symptoms are regulated by the interactive effects of soil texture, OM, and hydrology on N retention capacity (maximum pool size) and N retention kinetics (N retention rate). Down the hillslope gradient, soil solution nitrate (NO3) concentrations sampled with lysimeters increased, while 15NO3-N retention decreased. Landscape location (upland, hillslope, and toeslope) and soil type interacted to affect soil solution NO3 concentrations so that the downslope increase in NO3 was greater in sandy versus silty soils. These patterns manifest despite a downslope increase in soil organic carbon (SOC) and C/N ratios. A positive correlation between saturated hydraulic conductivity and soil solution NO3 sampled in zero-tension lysimeters during precipitation events suggested that high hydraulic conductivity promotes periodic rapid NO3 transport at rates that exceed retention kinetics. The downslope increase in soil solution NO3 in spite of a concomitant increase in SOC and C/N ratios provides an important contrast with previous N saturation research that highlights negative correlations between SOM C/N ratios and NO3 concentrations and suggests NO3 transport along connected hillslope flow paths may overwhelm stoichiometric sinks for inorganic N retention in SOM. Our results reveal important gaps in N retention theory based on SOM biogeochemistry alone and demonstrate how coupled biogeochemical and hydrological models can improve predictions of N saturation, particularly when considering periodic advective NO3 transport in the vadose zone. We show that in coarse-textured soils, low capacity for protection of SOM N by association with fine mineral particles interacts with rapid hydrological flushing of NO3 to enhance the expression of ecosystem N saturation symptoms.
    Journal of Geophysical Research: Biogeosciences 03/2013; 118(1):280-290. · 3.02 Impact Factor
  • Source
    Estudios en la Zona No Saturada ZNS’13, Edited by AGAIA, 11/2013; Universidad Santiago de Compostela., ISBN: 978-84-616-6234-0


Available from