Contents lists available at ScienceDirect Field Crops Research journal homepage: www.elsevier.com/locate/fcr Enhancement of root systems improves productivity and sustainability in water saving ground cover rice production system Yanan Zhang a,1 , Meiju Liu b,1 , Gustavo Saiz c , Michael Dannenmann c , Lin Guo a , Yueyue Tao a,b , Jianchu Shi a , Qiang Zuo a , Klaus Butterbach-Bahl c , Guoyuan Li d , Shan Lin a,d, ⁎ a College of Resources and Environment Sciences, China Agricultural University, Beijing 100193, China b College of Resources and Environment Sciences, Yunnan Agricultural University, Kunming 650201, China c Institute of Meteorology and Climate Research, Karlsruhe Institute of Technology (KIT-IMK-IFU), Garmisch-Partenkirchen 82467, Germany d College of Life Science and Technology, Hubei Engineering University, Hubei 432000, China ARTICLE INFO Keywords: Water-saving rice Ground Cover Rice Production System Root morphology Flowering stage Grain yield ABSTRACT In rice growing regions where water and temperature are growth limiting factors, the use of the innovative water-saving ground cover rice production system (GCRPS) leads to a substantial increase in yields and water use efficiency. However, so far the effect of GCRPS on root growth and its possible contribution to the observed increases in yield and water use efficiency remained unclear. In order to fill in this knowledge gap, we conducted a three-year experiment comparing two production systems: traditional paddy (Paddy) and GCRPS combined with two nitrogen fertilizer regimes (0, 150 kg N ha -1 ). The parameters investigated were root dry matter, length density and surface area at maximum tillering and flowering stage as well as grain yield and water use efficiency. Our study revealed the following findings: 1) Root dry matter, root length density and surface area were significantly higher in GCRPS than in Paddy at all soil depths. 2) Across the production systems, root dry matter, root length density and surface area at soil depth of 0–40 cm at flowering stage were significant posi- tively correlated to grain yield and total water use efficiency which suggested that improved root morphology traits, especially at flowering stage, contribute to higher grain yield and water use efficiency in GCRPS. Our results show that GCRPS has a positive effect on the development of rice roots and that the improved root development is of vital importance for higher yields. Furthermore, the improved root development in GCRPS may avoid potential lodging phenomena and increase soil organic carbon stocks, thus improving key soil functions. 1. Introduction Global agriculture nowadays is facing two major challenges: in- creasing food demand to feed the rapidly growing world population and declining global water resource availability (Bouman, 2007; Thakur et al., 2011). World population is estimated to reach nine billion by 2050. To feed an additional two billion people during the next 40 years major increases in crop production are needed (Ashikari and Ma, 2015). Rice, as one of the world's three major food crops, is the second most- produced cereal after maize. It represents 26% of harvested area and accounts for 31% of the overall production of the three major crops (rice, maize and wheat) (FAO, 2012). However, traditional paddy rice cultivation consumes more than half of the water used for irrigation in Asia (Bouman, 2001) and the water footprint, i.e. the amount of water needed to produce a quantity of grain is estimated to be 3 times higher than that of wheat and maize (Pimentel et al., 2004). Owing to such low irrigation water use efficiency and increasing requirement for rice production, the demand of irrigation water for rice production is pre- dicted to increase by 13.6% by 2025 (Rosegrant and Cai, 2002). However, the pressure on water is even further increasing, as 8–15% of fresh water currently used in agriculture will in the future be used to meet the growing domestic and industry water demand (Chartzoulakis and Bertaki, 2015). In order to meet the growing scarcity of fresh water for rice production, a series of water-saving technologies have been developed and tested. One of them is the so called Ground Cover Rice Production System (GCRPS), which was introduced in Central China in the late 20th century (Lin et al., 2002). In GCRPS the soil surface is covered during the entire growing season by a 5–7 μm thick plastic film. This plastic film minimizes soil water evaporative losses, increases soil temperature and reduces weed http://dx.doi.org/10.1016/j.fcr.2017.08.008 Received 12 May 2017; Received in revised form 7 August 2017; Accepted 9 August 2017 ⁎ Corresponding author at: College of Resources and Environmental Sciences, China Agricultural University, Beijing 100193, China. 1 These authors contributed equally to this work. E-mail address: linshan@cau.edu.cn (S. Lin).