Abstract
Rainfall simulations were conducted within mixed (cool- and native warm-season) grasslands in the sloping, rocky soils typical of the Ozark Mountains region to estimate nutrient and bacteria levels in runoff from biosolids and mineral fertilizer (MF). The ability of narrow (1 m) vegetated filter strips (VFS) to reduce losses was evaluated. Experiment 1 included an untreated control (C); 37 kg plant available nitrogen (PAN) ha−1from biosolids applied to the upslope half of the plot with the downslope half serving as a VFS (LBF); 74 kg PAN ha−1from biosolids, with VFS (HBF); and a uniform biosolids application at the lower rate and no VFS (LBU). Experiment 2 examined runoff from MF applied at 89 kg ammoniacal nitrogen (NH4-N) ha−1and 147 kg phosphorous (P) ha−1over the whole plot (MFW) or only on the upslope half (with VFS) (MFF). No significant differences were detected among mean fecal coliform levels despite large differences in magnitude. Losses of NH4-N and P were greater for LBU than for LBF. Although only marginally significant (P=0.058), total phosphorous contained in runoff was nearly three times higher in MFW than in MFF. Results of this study suggest that even a small VFS can potentially reduce nutrient levels in runoff.
Highlights
An estimated 226,800 dry tonnes of biosolids are produced each year in Missouri where 60% of the sludge is incinerated and 30% is applied to agricultural land [1]
It is important to observe that filtered treatments (LBF and HBF) had approximately one-fifth the colony-forming units (CFUs) concentration observed in LBU runoff (Figure 1)
Large variability in bacterial concentration has been reported by others [23, 30, 40] and feral animal or accidental introductions of fecal material to the plot areas may have contributed to variability; the contributions of such introductions would logically be small relative to contributions from biosolids treatments
Summary
An estimated 226,800 dry tonnes of biosolids are produced each year in Missouri where 60% of the sludge is incinerated and 30% is applied to agricultural land [1]. Most biosolids produced by the city of Springfield, Missouri, are applied to agricultural land. Many benefits and concerns associated with biosolids application to agricultural lands were recently reviewed by Torri et al [2] and Lu et al [3]. Biosolids provide recycled nutrients to soils and can serve as an alternative or a substitute to costly mineral fertilizers (MF).
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