Partial rootzone drying in sugarcane (Saccharum officinarum L.): effects on gas exchange, growth and water use efficiency

Sugarcane (Saccharum officinarum L.) is an effective crop for biomass production and is used mainly for sugar production and bio-fuel. Irrigation water has become less available in many regions due to global climate change and domestic. To confront the challenge of water utilization, there is a need to develop water-saving irrigation techniques in order to maximize crop water use efficiency. Partial rootzone drying (PRD) is a water-saving irrigation strategy that involves irrigating only part of the rootzone while leaving the other portion to dry to a predetermined level before the next irrigation. The objective of this study was to examine whether PRD affects photosynthetic capacity and growth in young sugarcane plants (48-day old). The experiment was conducted from January to April, 2011 in a greenhouse. Sugarcane mini-stalks were transplanted with divided root systems at 20 days of age into two pots. The pots were filled with soil (oxisol), sand and manure (1:1:1). The sugarcane plants were well-watered in the first 10 days after transplanting. Thereafter, the plants were exposed to three irrigation regimes: (1) Full irrigation (FI) (control); in which both soil compartments were watered to 100 % field capacity; (2) PRD; in which one soil compartment was watered to the field capacity while the other was allowed to dry for 17 days, then the plants were re-irrigated; (3) no irrigation (NI); in which both compartments were allowed to dry for 17 days, then re-irrigated. Net photosynthetic rate, stomatal conductance, transpiration, predawn leaf water potential, leaf area, shoot dry weight, root dry weight, root volume, and intrinsic water use efficiency were measured. PRD did not significantly reduce growth and gas exchange in comparison to FI, yet there was a 17.6 % reduction in water application. In addition, the agronomic water use efficiency was higher in PRD (4.1 g l−1) and FI (3.6 g l−1) than NI (2.9 g l−1). In this study, PRD irrigation reduced water consumption by 17.6 % with a total biomass reduction of 11.3 % as compared with fully watered plants. In conclusion, PRD may be an efficient irrigation strategy and promising for application in drought-prone regions for saving water where sugarcane is produced.