Growth of Root System and the Patterns of Soil Moisture Utilization in Sugarcane under Rain-fed and Irrigated Conditions in Sri Lanka

Abstract

The objective of this study was to investigate the effects of soil moisture deficits on the growth of root system and its effect on soil moisture utilization in sugarcane to identify relationship of root growth with drought tolerance of sugarcane varieties. An experiment with eight sugarcane varieties under rain-fed and irrigated conditions in a split-plot design was conducted from 2002 to 2007 at the Sugarcane Research Institute, Uda Walawe, Sri Lanka (6°21′N, 80°48′E). Root length densities (RLD) and soil moisture contents at different depths of the 1 m soil profile were measured. The variety SL 88 116 showed the highest RLD values of 1.49 in top (0–30 cm), 0.33 in middle (30–60 cm) and 0.65 cm cm−3 in entire (0–100 cm) layers of soil profile, and SL 83 06 showed the highest RLD of 0.14 cm cm−3 in the bottom (60–100 cm) layer of soil profile under rain-fed conditions. RLD of all varieties except SL 88 116 under irrigation were significantly (P < 0.05) greater (15–63%) than under rain-fed conditions. The rain-fed cane yield showed a significant (P < 0.05) positive correlation with RLD in the middle soil layer. Varieties with higher root length densities in the 30–60 cm soil layer survive better during significant water deficit periods in the top soil layer (0–30 cm), and such varieties produce high sugarcane yields in the rain-fed environments of Sri Lanka.