Contents lists available at ScienceDirect Soil & Tillage Research journal homepage: www.elsevier.com/locate/still Infiltration characteristics of lateritic vadose zones: Field experiments and modeling Madan K. Jha a , Smaranika Mahapatra a, ⁎ , Chinchu Mohan b , Chwadaka Pohshna a a AgFE Department, IIT Kharagpur, Kharagpur, 721 302, West Bengal, India b Department of Infrastructure Engineering, The University of Melbourne, Parkville, VIC, 3010, Australia ARTICLE INFO Keywords: Infiltration experiment Infiltration characteristics Infiltration model Field heterogeneity Vadose zone Lateritic terrain ABSTRACT Lateritic vadose zone, mostly found in tropical humid regions, is very complex and hence behaves in a different way than other vadose zones. Until now, little is known about the impact of agricultural practices on the in- filtration dynamics of such vadose zones. To this end, the present study was conceived to explore infiltration characteristics of lateritic soil-water zones by conducting 72 double-ring infiltration experiments at multiple sites considering both plot and field scales having paddy-wheat cultivation practices. Furthermore, five in- filtration models, two empirical (Kostiakov and Kostiakov-Lewis) and three process-based (Philip Two-Term, Swartzendruber and Brutsaert) were fitted to the site-specific infiltration data and their performance was cri- tically evaluated for modeling infiltration behavior of the lateritic vadose zone. Results indicated that the mean ‘quasi-steady infiltration rate’ of the Experimental Plot measured before paddy cultivation was about 0.23 ± 0.2 mm/min, which decreased by around 80% after paddy cultivation and then increases by more than 200% after wheat cultivation. Similarly, at the field scale, the ‘quasi-steady infiltration rate’ decreases by about 60% after paddy cultivation. The Swartzendruber model followed by the Brutsaert model provided the most reliable estimates of saturated hydraulic conductivity. The Swartzendruber, Brutsaert and Kostiakov-Lewis models showed a greater fitting ability in predicting ‘cumulative infiltration’ under all cultivation practices at both plot and field scales. In contrast, all the five infiltration models predicted infiltration rate with a lower accuracy than the cumulative infiltration. It is concluded that the infiltration characteristics of lateritic vadose zones are greatly influenced by cultivation practices as well as by macro-pores and low-permeability layers present in the soil profile. Given the significant field heterogeneity, future studies should explore the efficacy of other process-based infiltration models [e.g., the Smith and Parlange (1978) model, the Kutílek and Krejča model (1987), and the modified Green-Ampt models] in predicting the infiltration characteristics of lateritic terrains. 1. Introduction Groundwater is the most important natural resource for human life, socio-economic development and environmental sustainability. It is an important source of water to agricultural and urban users, and about a quarter of freshwater withdrawals of the world are contributed by groundwater. According to the World Water Development Report (WWAP, 2012), India is the largest consumer of groundwater in the world. Groundwater accounts for over 65% of irrigation water and 85% of drinking water supplies in India (Wyrwoll, 2012). Groundwater once considered as the abundant and economic resource that helped in a rapid development in the past is now depleting and is at the risk of pollution (Konikow and Kendy, 2005). Unmonitored and unregulated withdrawal of groundwater, especially for irrigation purposes has led to an alarming decline in several parts of the world and the situation is becoming increasingly serious in most developing nations including India. For ensuring sustainable management of groundwater, in-depth scientific investigation of groundwater encompassing both quality and quantity is essential. Proper knowledge about the hydraulic character- istics of vadose zones is a prerequisite to a comprehensive groundwater investigation because vadose zones constitute major pathways for in- filtrating and percolating water as well as for surface and subsurface pollutants. The movement of surface and atmospheric water to a groundwater system is appreciably controlled by the hydraulic char- acteristics of overlying vadose zones. In case of irrigated agriculture, the infiltration characteristics of the field are the key to efficient use of irrigation water by increasing application efficiency. In other words, detailed knowledge of infiltration characteristics is inevitable to reduce https://doi.org/10.1016/j.still.2018.12.007 Received 13 May 2018; Received in revised form 2 November 2018; Accepted 6 December 2018 ⁎ Corresponding author. E-mail addresses: madan@agfe.iitkgp.ac.in (M.K. Jha), smahapatra44@gmail.com (S. Mahapatra). Soil & Tillage Research 187 (2019) 219–234 0167-1987/ © 2018 Elsevier B.V. All rights reserved. T