ORIGINAL ARTICLE Phosphorus release kinetics in a soil amended with biosolids and vermicompost M. Islas-Espinoza • L. Solı ´s-Mejı ´a • M. V. Esteller Received: 26 June 2012 / Accepted: 8 May 2013 Ó Springer-Verlag Berlin Heidelberg 2013 Abstract Wastewater biosolids are large potential sources of macronutrients for agriculture, conservation and restora- tion of soils; there are, however, few studies on phosphorus (P) release in soils amended with biosolids. Biosolids and vermicomposted biosolids were tested in concentrations (5–30 g amendment kg -1 soil) equivalent to 18–100 Mg ha -1 . Desorption of P was determined by successive extrac- tions for 65 days. Soil P was low, and biosolid and vermi- compost addition released 8 and 6 times more P, respectively, than soil alone. To describe the release of P, zero-, first- and second-order equations, simple Elovich and power functions and the parabolic diffusion law were compared based on their coefficient of determination (r 2 ) and standard error (SE). In all treatments, the power function and especially the para- bolic diffusion law were the best fit, with 0.898–0.996 r 2 and 0.022–0.732 SE. The general behavior of the kinetic param- eters mostly depended on the amendment doses. Eutrophi- cation posited to start beyond 16 mg P kg -1 soil was more likely allayed by a maximum vermicompost dose of 50 Mg ha -1 , higher than the 36 Mg ha -1 maximum biosolid dose. The higher vermicompost P addition and lower P release could favor gradual and longer-term P absorption by plants and may reduce leaching or runoff P losses. Keywords Phosphorus  Biosolids  Vermicompost  Release kinetics  Soil Introduction Wastewater treatments produce biosolids (microbially digested sludge) which, under certain conditions, can add organic matter to soils (Franco-Herna ´ndez et al. 2003; Rostagno and Sosebee 2001), as well as P and other macro and micronutrients (Maguire et al. 2001; Solı ´s- Mejı ´a et al. 2012). Bioavailability of these nutrients to plants usually occurs through mineralization of organic matter present in biosolids, a process facilitated and accelerated by earthworms (Cardoso-Vigueros and Ram- ı ´rez-Camperos 2002). The earthworms’ metabolism and interaction with microorganisms convert organic waste into humus and other nutrients that induce plant growth (Capistra ´n et al. 2004). As the application rate of biosolids on agricultural land is often based on nitrogen content, the significant amounts of P in biosolids (Korboulewsky et al. 2002; Penn and Sims 2002) can exceed the needs of plants and soil microorganisms; water runoff or infiltration can cause eutrophication of surface water and groundwater pollution (Esteller et al. 2009; Penn and Sims 2002; Shober and Sims 2003). In soil amended with animal manure and sewage sludge, P release can be described by a power function (Siddique and Robinson 2004). P release kinetics in calcareous soils, amended and unamended with sewage sludge, fit first- order, Elovich, power and parabolic diffusion equations adequately (Hosseinpur and Pashamokhtari 2008). In other calcareous soils, amended with composted manure and pistachio, P release kinetics is best described by Elovich and power functions (Fekri et al. 2011). However, no reports have yet described P release in waste-amended sandy clay loam soils. Tropical soils subject to heavy seasonal rains have seldom been studied Electronic supplementary material The online version of this article (doi:10.1007/s12665-013-2549-y) contains supplementary material, which is available to authorized users. M. Islas-Espinoza (&)  L. Solı ´s-Mejı ´a  M. V. Esteller Centro Interamericano de Recursos del Agua (CIRA), Universidad Auto ´noma del Estado de Me ´xico, Cerro Coatepec, s/n, C.U., 50130 Toluca, Mexico e-mail: marinaislas@ymail.com 123 Environ Earth Sci DOI 10.1007/s12665-013-2549-y