Enzyme activities and diuron persistence in soil amended with vermicompost derived from spent grape marc and treated with urea Esperanza Romero *, Jesu ´ s Ferna ´ ndez-Bayo, Jean Manuel Castillo Dı ´az, Rogelio Nogales Environmental Protection Department, Estacio ´n Experimental del Zaidı´n (CSIC), C/Profesor Albareda 1, 18008 Granada, Spain 1. Introduction Soil functions are affected by the application of pesticides, mineral fertilizers, and organic amendments. However, little information is available on how the soil responds to the combined application of these agricultural inputs, which are commonly used in conventional farming systems. The use of agroindustrial wastes as organic soil amendments constitutes an effective waste-management strategy. However, most of these organic wastes require previous stabilization treatment. Vermicomposting is a low cost biotechnology that enhances the quality of fresh organic wastes, that are transformed into more humified material containing less toxic compounds (Nogales et al., 1995; Romero et al., 2006). The addition of vermicompost, especially to low OC content soils, plays a positive role because it increases organic matter content, stimulating microbial activity, and enhancing pesticide sorption and degrada- tion, thus minimizing negative side-effects (Ferna ´ ndez-Bayo et al., 2009a; Delgado-Moreno and Pen ˜a, 2009). However, the impact of this type of vermicompost on the biochemical parameters of farmed soil has rarely been assessed. Spent grape marc is an abundant winery-distillery waste (Chapman et al., 2001; Nogales et al., 2005) whose disposal raises environmental and health concerns. Previous studies of this waste material, either vermicomposted or not, have verified its ability to sorb non-ionic pesticides such as diuron. This capability was attributed to its composition and its humic-like substances (Romero et al., 2006). Later studies of diuron in soils amended with several vermicomposts have found spent grape marc to be the most effective vermicompost amendment for increasing the soil sorption capacity (Ferna ´ ndez-Bayo et al., 2009a). This increase in diuron sorption was related to the OC content and nature of the amendment used (lignin and humic acid contents), soil components such as clay type, which play an important role in the sorption process, and the chemical properties of diuron. However, the low stability of organic fractions of this vermicompost, attributed to its high content in acetic acid and furfural compounds found through pyrolysis gas-chromatography, modified its sorption efficiency after 6 weeks of incubation in soil but remained significantly higher than in unamended soils (Ferna ´ ndez- Bayo et al., 2009a). Unamended and organically amended agricultural soils are also supplemented with fertilizers such as urea to improve soil Applied Soil Ecology 44 (2010) 198–204 ARTICLE INFO Article history: Received 24 March 2009 Received in revised form 2 December 2009 Accepted 21 December 2009 Keywords: Soil Diuron Urea Vermicompost Enzyme activities Persistence Bioavailability ABSTRACT Mineral fertilizers, organic amendments, and pesticides are inputs commonly used in conventional farming practices. The aim of this study was to evaluate the effects of single or combined applications of spent grape marc-vermicompost, urea, and/or diuron on soil-enzyme activities and the persistence of this herbicide in soils with low organic carbon content. The application of vermicompost enhanced dehydrogenase (DHase) enzyme activity over time but altered soil urease activity to a very limited extent. The reduction in diuron concentrations and the increase in DHase activity indicated that the soil microorganisms were capable of degrading the ureic herbicide. Treatment with vermicompost and diuron had a stimulatory effect on soil microbial activity. On the whole, the application of diuron and urea to the vermicompost-amended soil raised DHase and urease activity to maximum levels (>3 mg INTF g 1 h 1 and >47 mg NH 4 + g 1 h 1 , respectively). The application of urea to the unamended and vermicompost- amended soil decreased diuron persistence from 18.8 and 33 d to 12.5 and 15 d, respectively. Our findings show that although vermicompost additions reduce diuron availability, this boosts diuron degradation when combined with urea. These additions, under different soil management conditions, minimize the bioavailability and persistence of diuron and consequently the risk of leaching and seepage into aquifers. Compared with untreated soils, these types of treated soils could also improve agricultural sustainability and the quality of the environment. ß 2009 Elsevier B.V. All rights reserved. * Corresponding author. Tel.: +34 958181600; fax: +34 958129600. E-mail address: eromero@eez.csic.es (E. Romero). Contents lists available at ScienceDirect Applied Soil Ecology journal homepage: www.elsevier.com/locate/apsoil 0929-1393/$ – see front matter ß 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.apsoil.2009.12.006