Soil health variability among residential landscapes impacts urban water conservation

Soil health or quality have been used synonymously to describe soil physical, chemical, and biological parameters. Soil quality/health is expected to improve over time, but few studies have determined those parameters from residential lawns in semiarid climates. The objectives were to 1) Determine physiochemical and microbiological attributes of urban soils established under turfgrass landscapes of different ages, and 2) Evaluate the importance of turfgrass management in structuring soil physiochemical properties and microbial communities. Soil samples were obtained from front lawns of residential homes within the following categories in 2018 (n=10) and 2019 (n=9): oldest (pre-1970), middle (1971-1990), newer (1991-2010), and newest (2011-present). Soil texture, bulk density, extractable nutrients, pH, soil organic matter (SOM), soil organic carbon (SOC) and total nitrogen (TN) were determined from soil collected in 2018. Soil microbial biomass and composition were determined for soil obtained in 2018 and 2019. Bulk density and pH were highest in newest homes and lowest in oldest homes, but no differences in CEC, K, Mg, or Ca were identified. Increasing home age increased SOM, SOC, TN, and microbial biomass regardless of management practices as determined by homeowner surveys and variation of visual quality of turfgrass within home age categories. Neither total FAMEs nor fungal composition differed for home age categories, but bacterial biomass increased with home age. Pairwise comparisons between home age categories using multi-response permutation procedures (MRPP) in Non-metric multidimensional scaling (NMS) ordination showed significant differences for 28 biomarkers except for middle and oldest home age categories. Management practices like irrigation, fertilization, and pesticides showed negligible influence on soil microbial composition based on non-parametric tests whereas no effect was observed for microbial biomass. The primary factor that affected accumulation of SOM, SOC, TN, and microbial biomass within landscapes was age of the residential home. Increased SOM and SOC in middle and oldest home age categories demonstrate reduced fertility and irrigation requirements to the lawns.