Agriculture, Ecosystems and Environment 142 (2011) 419–427 Contents lists available at ScienceDirect Agriculture, Ecosystems and Environment jo ur n al homepage: www.elsevier.com/lo cate/agee Short-term response of physical and chemical aspects of soil quality of a kaolinitic Kandiudalfs to agricultural practices and its association with microbiological variables Marcelo F. Fernandes a,∗ , Antonio Carlos Barreto a , Iêda C. Mendes b , Richard P. Dick c a Embrapa Coastal Tablelands, Av. Beira Mar 3250, Aracaju, SE 49025-040, Brazil b Embrapa Cerrados, BR 020 Km 18, Planaltina, DF, CEP 73310-970, Brazil c Ohio State University, School of Environment and Natural Resources, 210 Kottman Hall, 2021 Coffey Road, Columbus, OH 43210, USA a r t i c l e i n f o Article history: Received 18 April 2011 Received in revised form 3 July 2011 Accepted 4 July 2011 Available online 29 July 2011 Keywords: Cajanus cajan Fallow Hardsetting soil Intercropping Maize Soil tillage a b s t r a c t We evaluated the short-term (three years) impact of agricultural practices (soil tillage methods, maize cropping systems, and Brachiaria fallow) on the physical and chemical aspects of soil quality (SQ) of a kaolinitic Kandiudalfs in Northeastern Brazil, and the correlation between SQ and microbiological vari- ables. A forest site was also sampled as reference of undisturbed soil. SQ was evaluated by multivariate analyses of total and particulate organic matter carbon, cation exchange capacity, mean weigh diame- ter and percentage of water stable aggregates of soil samples (0–20 cm depth). Phospholipid fatty-acids were used to quantify microbial biomass (MB), fungi to bacteria ratio (F/B) and an indicator of bacte- rial stress (19:0cy/18:17c), whereas microbial enzyme activity was determined by the hydrolysis of fluorescein diacetate (FDA). A gradient of SQ, described by increases in the values of physical and chem- ical variables, was observed according to the sequence: cropped areas, irrespective to the agricultural practices < Brachiaria fallow < forest. SQ was positively correlated with MB, F/B and FDA, and negatively with 19:0cy/18:17c. F/B was more sensitive than SQ to the agricultural practices. In the short term, the physical and chemical aspects of the quality of a kaolinitic soil is restored by Brachiaria fallow, but is not affected by tillage methods or maize + pigeonpea intercropping. F/B ratio is a potential predictor of changes in the quality of kaolinitic soils in response to agricultural practices. © 2011 Elsevier B.V. All rights reserved. 1. Introduction Kaolinitic soils comprise over 70% of agricultural soils at low altitude in the tropics and are characterized by the high degree of weathering, a sandy to sandy loam surface horizon, a clayey B horizon, and the dominance of kaolinite (>90%) in the clay frac- tion (Juo and Franzluebbers, 2003). More specifically, kaolinitic soils with loamy sand or sandy loam surface horizon cover exten- sive areas in subhumid regions of Eastern and Western Africa, Southwestern India, and Northeastern Brazil, mainly in the coastal tablelands (Haynes, 1970; Juo and Franzluebbers, 2003). The agri- cultural potential of these soils is classified as moderate due to their weak aggregation, low organic matter content and low resistance to mechanical disturbances (Haynes, 1970; Juo and Franzluebbers, 2003; Chaer et al., 2009). A sharp deterioration of various properties ∗ Corresponding author. Tel.: +55 79 4009 1360; fax: +55 79 4009 1367. E-mail addresses: marcelo@cpatc.embrapa.br (M.F. Fernandes), barreto@cpatc.embrapa.br (A.C. Barreto), mendesi@cpac.embrapa.br (I.C. Mendes), dick.78@osu.edu (R.P. Dick). related to important soil functions (e.g. organic matter content, bulk density, saturated hydraulic conductivity, cation exchange capac- ity, aggregate mean diameter and water stability of aggregates) was observed in response to the increased frequency of tillage operations in a kaolinitic soil in Northeastern Brazil (Chaer et al., 2009). Thus, farming systems that exclude or minimize tillage oper- ations and increase plant residue inputs are essential to maintain or improve the quality and the production potential of these soils (Nyamadzawo et al., 2008, 2009; Juo and Franzluebbers, 2003). Although the successions between cash and cover crops, espe- cially legumes, have been pointed out as an effective strategy for increasing the input of residues in the soil (Bayer et al., 2006; Zanatta et al., 2007), this practice is not feasible in various regions of the subhumid and semi-arid tropics due to the relatively short rainy season, which does not allow double cropping. In these regions, the intercropping between row and cover crops may represent a viable solution to this climate limitation, as long as the competi- tion between the plant species is not high. Because of its slow initial growth rate, pigeonpea (Cajanus cajan) has a high temporal comple- mentarity of resources with maize and is an interesting alternative for intercropped use with this crop (Barreto and Fernandes, 2010). 0167-8809/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.agee.2011.07.002