Biol Fertil Soils (2003) 37:124–129 DOI 10.1007/s00374-002-0568-z ORIGINAL PAPER Maria Teresa Dell’Abate · Anna Benedetti · Alessandra Trinchera · Daniele Galluzzo Nitrogen and carbon mineralisation of leather meal in soil as affected by particle size of fertiliser and microbiological activity of soil Received: 28 June 2002 / Accepted: 11 November 2002 / Published online: 13 December 2002  Springer-Verlag 2002 Abstract Carbon and nitrogen mineralisation of leather meal fertilisers were studied in two soils characterised by different respiration activity. Both C and N mineralisation were highest in the most active soil, and when leather meal was added as a powder rather than as 2- to 4- and 4- to 6-mm particles. Fast and slow soluble N pools were determined after extraction with cold water and with hot buffer, respectively. The N remaining after the second extraction with hot buffer was named slow-release N. The percentage of slow-release N rose as the size of the applied leather meal particles increased, whereas fast soluble N was highest in the coarsest (4–6 mm) fertiliser. Keywords Organic fertilisers · Leather meal · N slow release · C and N mineralisation · Soil biological fertility Introduction It is well known that the use of organic fertilisers in agriculture can improve plant nutrient absorption by modulating the actual reservoirs of nutrients in relation to the mineralisation processes regulated by soil microbiota (Sequi and Benedetti 1995). In particular, organic fertil- isation is useful in the Mediterranean area where pedo- climatic conditions, such as water deficit and scarce soil organic matter content, determine a low microbiological activity for soil. Leather meal represents a large amount of organic biomass derived from the leather tanning industry. The annual production of leather meal in Italy is almost constant over time, according to the Italian Association of Leather Meal Fertiliser producers (CO.VA.COR.). In 1993 (last official monitoring), 75,000 t leather meal were produced in Italy, of which 40% was used as N fertiliser, 33% was exported to European Union countries as organic matrices to produce organic-mineral fertilisers, 26% was used in Italy to produce organic-mineral fertilisers, and 1% was exported out of the EU (Benedetti and Ciavatta 1998). Other leather-meal-producing coun- tries are USA (22,000 t), Korea (10,000 t) and Poland (6,000 t). Due to the high organic N and C contents, leather meal is classified as an organic N fertiliser under Italian law (Italian Law no. 748/84). In the past, there was concern about the use of leather meal as a fertiliser due to the presence of trivalent chromium (Benedetti et al. 1992; Canali et al. 1997). However, it has been shown that Cr 3+ is not dangerous to humans, animals or the environment (Santoprete 1997). Collagen, a high molecular weight fibrous protein, is the main component of leather meal and can release organic C and N after hydrolysis. Both C and N can be utilised as energy sources by soil heterotrophic micro-organisms. The agronomic benefits derived from leather meal fertilisation depend on both the proteic composition of the leather and on the microbio- logical activity of the soil (Benedetti et al. 1991). High C and N mineralisation rates usually occur in soils with high levels of microbiological activity. In addition, like any particulate organic material, mineralisation may depend on the size of the particles added to the soil. Optimal use of an organic N fertiliser for soil should be based on the slow release of the available N so as to significantly reduce N loss and guarantee the crop with an adequate N supply throughout the entire vegetative cycle (Benedetti 1983). To date there are no well-established analytical methods for determining the slow release N pools of organic fertilisers and how these pools are affected by the microbiological activity of the soil. Benedetti et al. (1994) proposed a modified Stanford and Smith method to determine potential N mineralisation of organic materials, but this method alone does not give information on the number and size of the different N pools involved in N mineralisation. The aim of the present paper was to study the C and N mineralisation of three hydrolysed leather meal fertilisers characterised by different granulometries, added to two M. T. Dell’Abate ( ) ) · A. Benedetti · A. Trinchera · D. Galluzzo Istituto Sperimentale per la Nutrizione delle Piante, Via della Navicella 2/4, 00184 Rome, Italy e-mail: mt.dellabate@isnp.it Tel.: +39-06-7008721 Fax: +39-06-7005711