Assessing the soil quality of long-term reclaimed wastewater-irrigated cropland

The properties of soils may be characterized by many attributes. However, there is not a systematic procedure to objectively select the measurement parameters that may be used to assess soil quality. Following the data collection, it is often a dilemma to decide how many and which of the measured parameters should be included in the assessment as the outcomes may be influenced by the parameters included. In this study, 29 physical, chemical, and biological attributes of soils at a longterm reclaimed wastewater-irrigated field in Bakersfield, CA and its adjacent non-wastewaterirrigated control were determined with samples collected along a 100-m transect at 1-m interval. The fields have been cultivated with varieties of field crops over the past 70 years. The spatial variability of the data was evaluated. The principal component method was employed to identify the soil attributes that were most significant in describing variances of the fields. Soil quality of the treated and control fields were compared using the principal components identified in this process. Results indicated that the soil quality might be evaluated by comparing the total porosity (or drainable porosity), pH, electrical conductivity (EC), magnesium (Mg), phosphorus (P), and zinc (Zn) of soils in the control and the treated fields. Except for the total porosity and Mg, the other soil parameters of the control and treated fields were not significantly different. While the soils of both fields support successful crop production, the reclaimed wastewater irrigation appeared to slightly increase the soil compaction and reduce the soil’s capacity of holding nutrient elements, such as Mg. D 2003 Elsevier Science B.V. All rights reserved.