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On-Site Assessment of Extractable Soil Nutrients after Long-Term Biosolid Applications to Perennial Forage

Haney, Richard L., Jin, Virginia L., Johnson, Mari-Vaughn V., White, Michael J., Arnold, Jeffrey G.
Communications in soil science and plant analysis 2015 v.46 no.7 pp. 873-887
Cynodon dactylon, application rate, biosolids, forage, forage production, magnesium, mineralization, nitrates, nitrogen, orthophosphates, phosphorus, pollution load, potassium, recycling, soil nutrients, soil profiles, Texas
The objective of this study was to evaluate soil nutrient loading and depth distributions of extractable nitrogen (N), phosphorus (P), and potassium (K) after long-term, continuous annual surface applications of anaerobically digested class B biosolids at a municipal recycling facility in central Texas. Commercial forage production fields of coastal bermudagrass (Cynodon dactylon L.) were surface applied at 0, 20, 40, or 60 Mg dry biosolids ha ⁻¹ y ⁻¹ for 8 years. Application duration was evaluated in fields treated with 20 Mg dry biosolids ha ⁻¹ y ⁻¹ for 0, 8, or 20 years. Total soil loads of extractable inorganic N and P increased linearly with application rate, but only extractable P increased with duration. Neither total load nor soil distribution of extractable K was affected by biosolid applications. Mineralization of biosolid-derived organic N and P likely contributed to elevated concentrations of nitrate throughout the soil profile (0–110 cm) and orthophosphate in surface soils (0–40 cm).