Effect of different levels of drought during the formative phase on growthparameters and its relationship with dry matter accumulation in sugarcane

A field experiment was conducted at Coimbatore(11 degrees N, 77 degrees E), India during the 1996 and 1997 crop seasons, using four commercial sugarca ne varieties (Co 8021, Co 419, Co 8208 and Co 6304), to study the effect of three levels of drought (severe, moderate and control) during the formativ e phase (60-150 days after planting) on growth determinants and their relat ionship with dry matter accumulation. The reduction in dry matter content w as 60.8, 52.4 and 25.9 % in severe drought and 46.3, 36.3 and 15.1 % in mod erate drought at the ends of the formative, grand growth and maturity phase s, respectively. High net assimilation rate, optimum leaf area index: high crop growth rate and an early shift in dry matter allocation to the stem we re found to be desirable for higher biomass production, especially under wa ter-limited drought conditions. Measurement of growth parameters such as ne t assimilation rate, relative growth rate, leaf area index and leaf area du ration under drought and crop growth rate and stalk elongation rate under n ormal irrigated conditions, particularly during the formative phase, might help to predict total dry matter at harvest. Leaf area ratio was not found to correlate with total dry matter at harvest in either drought or normal i rrigated conditions.