Characterizing roots and water uptake in a ground cover rice production system

BACKGROUND AND AIMS Water-saving ground cover rice production systems (GCRPS) are gaining popularity in many parts of the world. We aimed to describe the characteristics of root growth, morphology, distribution, and water uptake for a GCRPS. METHODS A traditional paddy rice production system (TPRPS) was compared with GCRPS in greenhouse and field experiments. In the greenhouse, GCRPS where root zone average soil water content was kept near saturation (GCRPSsat), field capacity (GCRPSfwc) and 80% field capacity (GCRPS80%), were evaluated. In a two-year field experiment, GCRPSsat and GCRPS80% were applied. RESULTS Similar results were found in greenhouse and field experiments. Before mid-tillering the upper soil temperature was higher for GCRPS, leading to enhanced root dry weight, length, surface area, specific root length, and smaller diameter of roots but lower water uptake rate per root length compared to TPRPS. In subsequent growth stages, the reduced soil water content under GCRPS caused that the preponderance of root growth under GCRPSsat disappeared in comparison to TPRPS. Under other GCRPS treatments (GCRPSfwc and GCRPS80%), significant limitation on root growth, bigger root diameter and higher water uptake rate per root length were found. CONCLUSIONS Discrepancies in soil water and temperature between TPRPS and GCRPS caused adjustments to root growth, morphology, distribution and function. Even though drought stress was inevitable after mid-tillering under GCRPS, especially GCRPS80%, similar or even enhanced root water uptake capacity in comparison to TPRPS might promote allocation of photosynthetic products to shoots and increase water productivity.