Temporal dynamics of soil hydraulic properties and the water-conducting porosity under different tillage Andreas Schwen a, *, Gernot Bodner b , Peter Scholl b , Graeme D. Buchan c , Willibald Loiskandl a a Institute of Hydraulics and Rural Water Management, University of Natural Resources and Life Sciences (BOKU), Muthgasse 18, 1190 Vienna, Austria b Institute of Agronomy and Plant Breeding, University of Natural Resources and Life Sciences (BOKU), Gregor-Mendel-Strasse 33, 1180 Vienna, Austria c Soil and Physical Sciences Department, Lincoln University, Christchurch, New Zealand 1. Introduction Soil cultivation practices affect soil hydraulic properties and processes dynamically in space and time with consequences for the storage and movement of water, nutrients and pollutants, and for plant growth (Strudley et al., 2008). For given climatic conditions and a particular soil–plant system, both the tillage practice and irrigation system can alter the soil structure (Messing and Jarvis, 1993). Thus, understanding the temporal and management-induced changes that soil hydraulic properties undergo is important for sound land management and for modeling nutrient or contaminant transport (Angulo-Jaramillo et al., 1997; Hu et al., 2009; Yoon et al., 2007). The impact of different cultivation techniques on soil hydraulic properties has been frequently studied in recent decades (Ndiaye et al., 2007; Sauer et al., 1990; Strudley et al., 2008). However, the literature clearly shows that the impact of different tillage practices on soil hydraulic properties is not consistent across locations, soils, and experiment designs (Moret and Arrue, 2007a; Strudley et al., 2008). Moreover, most publications document averaged comparisons between different tillage practices and do not take into account the spatial and temporal dynamics (Angulo- Jaramillo et al., 1997; Strudley et al., 2008). Only few published studies address both the temporal and management-induced changes in soil hydraulic properties (Alletto and Coquet, 2009; Soil & Tillage Research 113 (2011) 89–98 ARTICLE INFO Article history: Received 13 January 2011 Received in revised form 14 February 2011 Accepted 18 February 2011 Available online 21 March 2011 Keywords: Soil tillage Tension infiltrometer Hydraulic properties Water-conducting porosity Temporal variability ABSTRACT Soil hydraulic properties are subject to temporal changes as a response to both tillage and natural impact factors. As the temporal and spatial variability might exceed cultivation-induced differences, there is a need to better differentiate between those influence factors. Thus, the objective of the present study was to assess the impact of different tillage techniques – conventional (CT), reduced (RT), and no-tillage (NT) – on the soil hydraulic properties and their temporal dynamics. On a silt loam soil, tension infiltrometer measurements were obtained frequently over two consecutive years. The data was analyzed in terms of the near-saturated hydraulic conductivity, inversely estimated parameters of the van Genuchten/ Mualem (VGM) model, and the water-conducting porosity. Our results show that the near-saturated hydraulic conductivity was in the order CT > RT > NT, with larger treatment-induced differences where water flow is dominated by mesopores. The VGM model parametera VG was in the order CT < RT < NT, with high temporal variations under CT and RT, whereas the parameter n was hardly affected. NT resulted in the greatest water-conducting pore radii, whereas no distinct differences were observed between CT and RT. The results give indirect evidence that NT leads to greater connectivity and smaller tortuosity of macropores, possibly due to a better established soil structure and biological activity. NT also resulted in a better temporal stability of both the pore network and the hydraulic properties, but showed the highest spatial variability of macropores. We suggest that the hydraulically effective pores decreased after tillage in response to rainfall during winter, and gradually increased in spring and summer induced by biological activity, root development and wetting/drying cycles. A multivariate ANOVA revealed that variations in mesopore-related quantities could be explained sufficiently by an interaction of tillage and time. By contrast, due to high spatial variability, macropore-related quantities could not be explained by those influence factors. The study reveals the importance of the temporal dynamics for both hydraulic properties and the water-conducting porosity. ß 2011 Elsevier B.V. All rights reserved. Abbreviations: CV, coefficient of variation; MS, mean square of the effect; CT, conventional tillage; RT, reduced tillage; NT, no-tillage; VGM, van Genuchten/ Mualem model. * Corresponding author. Tel.: +43 1 47654 5488; fax: +43 1 47654 5499. E-mail addresses: Andreas.Schwen@boku.ac.at (A. Schwen), Gernot.Bodner@boku.ac.at (G. Bodner), Peter.Scholl@boku.ac.at (P. Scholl), Graeme.Buchan@lincoln.ac.nz (G.D. Buchan), Willibald.Loiskandl@boku.ac.at (W. Loiskandl). Contents lists available at ScienceDirect Soil & Tillage Research journal homepage: www.elsevier.com/locate/still 0167-1987/$ – see front matter ß 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.still.2011.02.005