Altered Rice Root System Characteristics to Cope Scanty Water by Drip Irrigation

Water saving irrigation regimes needed to deal with a reduced availability of water for rice production. Root traits are the key in soil moisture uptake and may be improved to limited water regimes. A field investigation was conducted with two rice genotypes [TNRH 180 and PMK(R)3] to evaluate the hidden half traits under drip irrigation methods [drip (DI), subsurface drip (SDI) with three irrigation regimes (100, 125 and 150% Pan Evaporation (PE))] and a conventional surface irrigation (control). The results showed that higher total root length was noticed under drip irrigation than conventional surface irrigation. In the case of moderate irrigation regimes (125% PE), the root length density increased at 10-20 cm soil layer and decreased with well moisture (150% PE) and stressed (100% PE) irrigation regimes. In addition, the SDI system with 125 % PE improved the root traits [total root length (44.8 and 37.0 m hill^-1), root volume (54.3 and 48.0 cc hill^-1), root length density (1.69 and 1.53 cm cm^-3), root mass density (1.29 and 1.33 mg cm^-3) and root:shoot ratio (0.22 and 0.17), respectively] of TNRH 180 and PMK(R)3 than the conventional irrigation. Similar SDI system showed comparable root results even under stressed (100% PE) irrigation regimes. Higher root oxidation activity was observed in 125% PE especially through SDI, might be due to better oxygen supply to the root system with potential advantages for water and nutrient uptake. Therefore, altered rice root traits, root oxidation activity could be the key factor to cope limited water and reasoned for the aboveground agronomic performance and yield under drip irrigation.