Biosolids land application was demonstrated to be a potentially cost‐effective means for restoring forage productivity and enhancing soil‐moisture‐holding capacity on disturbed rangelands. By land‐applying aerobically digested, anaerobically digested, composted, and lime‐stabilized biosolids on rangeland test plots at rates of up to 20 times (20X) the estimated nitrogen‐based agronomic rate, forage yields were found to increase from 132.8 kg/ha (118.2 lb/ac) (control plots) to 1182.3 kg/ha (1052.8 lb/ac).
Despite the environmental benefits associated with increased forage yield (e.g., reduced soil erosion, improved drainage, and enhanced terrestrial carbon sequestration), the type of forage generated both before and after biosolids land application was found to be dominated by invasive weeds, all of which were characterized as having fair to poor nutritional value. Opportunistic and shallow rooting invasive weeds not only have marginal nutritional value, they also limit the establishment of native perennial grasses and thus biodiversity. Many of the identified invasive species (e.g., Cheatgrass) mature early, a characteristic that significantly increases the fuel loads that support the increased frequency and extent of western wildfires.

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The state of Utah has been concerned about excess P in soils that had received biosolids application, especially at loading rates that exceed crop nutrient requirements. The biosolids loading rates have been based on N crop requirements, which results in excess P in biosolidsamended soils. Therefore, the mobility of phosphorus in biosolids-amended soils in western Utah was investigated to address this issue. Three different types of biosolids including lime stabilized, aerobically digested, and anaerobically digested biosolids were land applied on 1/3-acre test plots at a variety of application rates (up to twenty times the estimated agronomic rate). The total P appeared to accumulate in the soil surface (i.e. 0.75 ft) for all different biosolidsamended soils. Accumulation of total P at the further soil depths (i.e. 0.75, 2, 3, 4, and 5 ft) was lower than that of the soil surface. No consistent trend was found with respect to the change of total P in terms of time (i.e. Year 1 and Year 2 following biosolids application). The accumulation of the plant available P (Olsen P) along the soil depths exhibited the same tendency with that of the total P. The P leachability from biosolids land application was low because the ratios of total P to Al+Fe were below 1 in all biosolids-amended test plots. The biomass yields at the test sites were enhanced as compared against the control. It was concluded that N-based biosolids land application did not result in significant P leachability that could pose a risk to the ground water source, human health, and the environment.

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