Mixed-species legume fallows affect faunal abundance and richness and N cycling compared to single species in maize-fallow rotations Gudeta Sileshi a, * , Paramu L. Mafongoya b , R. Chintu c , Festus K. Akinnifesi a a World Agroforestry Centre (ICRAF), SADC-ICRAF Agroforestry Programme, Chitedze Agricultural Research Station, P.O. Box 30798, Lilongwe, Malawi b 11 Mcglew Road, Mt Pleasant, Harare, Zimbabwe c Participatory Ecological Land Management (PELUM) Association, PELUM Zambia, P.O. Box 30443, Lusaka, Zambia article info Article history: Received 26 March 2008 Received in revised form 18 August 2008 Accepted 9 September 2008 Available online 12 October 2008 Keywords: Cajanus Litter Decomposition Sesbania Tephrosia Zambia Soil mineral N Soil fauna abstract Rotation of nitrogen-fixing woody legumes with maize has been widely promoted to reduce the loss of soil organic matter and decline in soil biological fertility in maize cropping systems in Africa. The objective of this study was to determine the effect of maize-fallow rotations with pure stands, two- species legume mixtures and mixed vegetation fallows on the richness and abundance of soil macro- fauna and mineral nitrogen (N) dynamics. Pure stands of sesbania (Sesbania sesban), pigeon pea (Cajanus cajan), tephrosia (Tephrosia vogelii), 1:1 mixtures of sesbania þ pigeon pea and sesbania þ tephrosia, and a mixed vegetation fallow were compared with a continuously cropped monoculture maize receiving the recommended fertilizer rate, which was used as the control. The legume mixtures did not differ from the respective pure stands in leaf, litter and recycled biomass, soil Ca, Mg and K. Sesbania þ pigeon pea mixtures consistently increased richness in soil macrofauna, and abundance of earthworms and milli- pedes compared with the maize monoculture (control). The nitrate-N, ammonium-N and total mineral N concentration of the till layer soil (upper 20 cm) of pure stands and mixed-species legume plots were comparable with the control plots. Sesbania þ pigeon pea mixtures also gave higher maize grain yield compared with the pure stands of legume species and mixed vegetation fallows. It is concluded that maize-legume rotations increase soil macrofaunal richness and abundance compared with continuously cropped maize, and that further research is needed to better understand the interaction effect of mac- rofauna and mixtures of organic resources from legumes on soil microbial communities and nutrient fluxes in such agro-ecosystems. Ó 2008 Elsevier Ltd. All rights reserved. 1. Introduction Soil fauna play a significant role in litter decomposition, nutrient mineralization and improvement of soil properties (Ha ¨ ttenschwiler and Gasser, 2005; Lavelle et al., 2003; Oue ´ draogo et al., 2007). Macrofauna such as earthworms, termites, millipedes and beetles process large amounts of plant material and determine the fate of litter in many ecosystems (Ha ¨ttenschwiler and Gasser, 2005; Jones, 1990; Rawlins et al., 2006). However, plant community structure has a strong impact on soil faunal communities and their activities (Laossi et al., 2008; Lavelle et al., 2003). The inclusion of nitrogen-fixing plants in agro-ecosystems has been shown to sustain ecosystem functions and productivity of land (Kahindi et al., 1997; Laossi et al., 2008; Simms and Taylor, 2002). In Africa, the rotation of nitrogen-fixing woody legumes with maize has been widely promoted in order to improve soil fertility (Mafongoya et al., 2006; Sileshi et al., 2008). These are known as legume ‘‘improved fallows’’ to distinguish them from the natural fallows that depend on regeneration of mixed vegetation (Sileshi et al., 2008). Recent research suggests that rotations with mixed-species fallows are preferable in agronomic terms over pure stands due to synergy between above and belowground resource acquisition (Chirwa et al., 2003; Gathumbi et al., 2002). Theoretical predictions also show that greater plant diversity leads to greater resource use and thus greater total community biomass (Tilman et al., 1997). The greater resource use associated with plant diver- sity would reduce nutrient losses, leading to long-term increases in ecosystem carbon and nutrient stores, which will also increase productivity (Tilman et al., 1997). Decomposition of litter from a given species changes greatly in the presence of mixed litter incorporating other species (Ha ¨t- tenschwiler and Gasser, 2005). Hence, litter diversity could influ- ence the community structure of macrofauna (Laossi et al., 2008) and ecosystem functions such as litter decomposition and nutrient cycling. Litter diversity could influence community structures and * Corresponding author. POST DOT NET, P.O. Box X389, Cross Roads, Lilongwe, Malawi. Tel.: þ265 170 7329; fax: þ265 170 7323; Mobile: þ265 964 2149. E-mail address: sgwelde@yahoo.com (G. Sileshi). Contents lists available at ScienceDirect Soil Biology & Biochemistry journal homepage: www.elsevier.com/locate/soilbio 0038-0717/$ – see front matter Ó 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.soilbio.2008.09.007 Soil Biology & Biochemistry 40 (2008) 3065–3075