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Measuring and estimating sulfur mineralization potential in soils amended with poultry litter or inorganic fertilizer

Wyngaard, Nicolás, Cabrera, Miguel L.
Biology and fertility of soils 2015 v.51 no.5 pp. 545-552
ammonium compounds, clay fraction, labor, long term effects, mineral fertilizers, mineralization, nitrogen, potassium chloride, poultry manure, sodium bicarbonate, soil amendments, sulfur, wet-dry cycles, Delaware, Georgia, Iowa
The effect of long-term (more than 10 years) application of poultry litter (PL) or inorganic fertilizer (IF) on sulfur (S) mineralization potential (Sₒ) was evaluated using four different soils (Delaware 1, Delaware 2, Iowa, and Georgia). Also, different methods to estimate S availability (extraction with KCl, NaHCO₃, and KCl after a wetting-drying cycle, aerobic incubations for 7 and 14 days, and NH₄ ⁺ quantification after an anaerobic incubation) were compared to Sₒ. When compared to long-term application of IF, long-term application of PL generated an increase in total soil S ranging from 0 to 0.14 g kg⁻¹, which was positively associated with the soil clay content (R ² = 0.98), and resulted in an increase in Sₒ ranging from 0 to 21.2 g kg⁻¹. From the evaluated methods to estimate Sₒ, only three of them were significantly (p < 0.05) correlated to Sₒ: aerobic incubation for 7 days (r = 0.85), extraction with NaHCO₃ (r = 0.85), and nitrogen anaerobic incubation (r = 0.99). Based on the reduced time and labor involved and in their capacity to distinguish between treatments, we recommend further use and further evaluation of the last two methods as estimators of Sₒ.