Applied Soil Ecology 46 (2010) 464–469 Contents lists available at ScienceDirect Applied Soil Ecology journal homepage: www.elsevier.com/locate/apsoil Selection of phosphorus solubilizing bacteria with biocontrol potential for growth in phosphorus rich animal bone charcoal J. Postma a,∗ , E.H. Nijhuis a , E. Someus b a Plant Research International, P.O. Box 69, 6700 AB Wageningen, The Netherlands b Terra Humana Ltd., Széchenyi u. 59, H-1222 Budapest, Hungary article info Article history: Received 4 August 2010 Received in revised form 24 August 2010 Accepted 26 August 2010 Keywords: Biological control Phosphorus mobilization Antagonistic bacteria Animal bone charcoal Pythium aphanidermatum Fusarium oxysporum f.sp. radicis lycopersici abstract Bacteria with the ability to solubilize phosphorus (P) and to improve plant health were selected and tested for growth and survival in P-rich animal bone charcoal (ABC). ABC is suggested to be suitable as a carrier for biocontrol agents, offering them a protected niche as well as delivering phosphate to plants, meanwhile re-using P from waste of the food chain. Ninety-seven bacterial isolates from different soils were tested for their potential to dissolve P from ABC. Of these isolates, 60% showed positive scores; they belonged to the genera Arthrobacter, Bacillus, Burkholderia, Collimonas, Paenibacillus, Pseudomonas, Serratia, and Streptomyces. Twelve isolates from different taxonomic groups were selected for further research on growth ability and survival in ABC, and on their potential to control plant pathogens. The highest concentrations of P were dissolved by Pseudomonas chlororaphis and Bacillus pumilus, followed by Paenibacillus polymyxa, Burkholderia pyrrocinia and three Streptomyces isolates. P. chlororaphis and P. polymyxa showed strongest growth inhibition of plant pathogenic Pythium and Fusarium sp., followed by the Streptomyces spp. isolates. © 2010 Elsevier B.V. All rights reserved. 1. Introduction Researchers and politicians become increasingly aware of future depletion of economically recoverable phosphate reserves (Cordell et al., 2009). Modern agriculture is using increasing amounts of phosphorus (P) derived from phosphate rock, which is a non- renewable resource. Current global reserves may be depleted in 50–100 years (Cordell et al., 2009). Since P is an essential element for plant growth, there is an urgent need to look for alternative and renewable sources of P. Animal bones are a source of P that can be recycled. The nitrogen in bones, as well as in other animal waste products, can facilitate composting processes of carbon rich ligno-cellulosic wastes (Cayuela et al., 2009). Bones have always been regarded as a valuable manure, but have been little used in commercial agriculture since the 1950s (Warren et al., 2009). New technologies producing safe P fertilizers from animal bones will facilitate the recycling of P from food industrial waste. Carbonization of animal bone meal, i.e. heat treatment up to 850 ◦ C, results in a porous product which is called animal bone charcoal (ABC). It mainly consists of P and calcium (Ca). Due to the high temperature, any risk of transmitting diseases is practically neglectable. ABC is a P fertilizer of solubility intermediate between ∗ Corresponding author. E-mail address: joeke.postma@wur.nl (J. Postma). Gafsa phosphate rock and triple superphosphate fertilizer (Warren et al., 2009). The fraction of P dissolved from ABC in different soils ranges from 0 to 73% in 145 days, depending on soil characteris- tics such as pH and P sorption of the soil (Warren et al., 2009). However, P solubility might be improved by simultaneous appli- cation of micro-organisms. Several soil bacteria, as well as fungi, e.g. Burkholderia, Bacillus, Pseudomonas, Streptomyces, Aspergillus, Paenibacillus and Trichoderma spp., are known to dissolve inorganic phosphorus (Hamdali et al., 2008a; Kim et al., 2008; Kim et al., 2005; Kucey et al., 1989; Vassilev et al., 2006). Soil bacteria are also known for their capacity to improve plant growth or health through several other mechanisms. Frequently described antagonistic bacteria with the ability to control plant pathogenic fungi and oomycetes are Pseudomonas, Serratia, Bacil- lus, and Streptomyces spp. (Fravel, 2005; Paulitz and Bélanger, 2001; Whipps, 2001). Other bacteria are known to enhance plant growth by producing phytohormones; e.g. Burkholderia, Pseudomonas, Bacillus, and Paenibacillus spp. (Kilian et al., 2000; Sessitsch et al., 2004, 2005; Vonderwell et al., 2001). In few studies, biocontrol or plant-growth promoting activities and phosphorus mobilizing potential of bacteria are combined, either in one organism (Hamdali et al., 2008b; Vassilev et al., 2006) or by combining micro-organisms with different beneficial properties (Rudresh et al., 2005). The porous structure of ABC is an ideal carrier to harbor micro- organisms (Someus, 2004). ABC has a large specific surface area and micro-organisms grown in such a matrix are protected against the harsh environment, when introduced into soil. Moreover, ABC 0929-1393/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.apsoil.2010.08.016