Biological soil crusts enhance moisture and nutrients in the upper rooting zone of sandy soil agroecosystems

Abstract

AbstractBackground: Biological soil crusts (biocrusts) are commonly found in arid ecosystems and are known to have increased carbon (C) and nitrogen (N) concentrations compared to non‐crusted soil. Similar biocrusts were recently identified in Florida, USA sandy soil agroecosystems where they could impact soil biogeochemical cycling, particularly of C and N, in the crop rooting zone.Aims: Therefore, this research assessed the impacts of biocrusts on soil moisture, available and microbial C and N concentrations, and soil stable N isotopic ratios (δ15N) in the upper rooting zone (0–15 cm) below biocrusts compared to nearby control bare soils without biocrusts.Methods: Intact soil cores (0–15 cm) were collected from crusted and non‐crusted (control) locations in three sandy soil, citrus agroecosystems. Soil cores were partitioned into three depths: a surface (0–1 cm), a middle (1–5 cm), and a subsurface depth (5–15 cm), and were analyzed for soil moisture and multiple C and N cycling pools.Results: Biocrust presence and sampling depth (0–1 cm, 1–5 cm, and 5–15 cm) had significant impacts on soil physical, chemical, and biological parameters at the sites. All sites had increased bulk total C and total N, soluble (ammonium, nitrate, dissolved organic N, and salt extractable C), and microbial (microbial biomass C/N) C and N concentrations in the biocrust surface depth compared to the control without biocrusts. Nitrate and total inorganic N (ammonium + nitrate) were enriched below biocrusts (1–5 cm) with one site having 96% and 71% more nitrate and total inorganic N, respectively, under biocrusts compared to controls. This additional plant‐available N was likely provided by the biocrust, as indicated by the δ15N. Further, the soil below biocrusts (1–5 cm) at one agroecosystem had 44% more microbial biomass C and a significantly lower MBC:MBN than soil without biocrusts.Conclusions: Overall, results illustrate these naturally occurring biocrusts have the potential to benefit agroecosystems by enriching soil C and N in the crop rooting zone, indicating the potential for biocrusts to effect overall soil quality and health.