Efficiency of Chemical Ripener Action in Sugarcane. III. Growth and Qualitative Effects of Polaris as a Function of the Number and Frequency of Applications

Abstract

The efficiency of Polaris (N,N-bis [phosphonomethyl] glycine) in modifying sugarcane quality, yield, and growth was studied with early-adult plants propagated in sand culture. A single quantity of the ripener administered in one dose served as the standard Polaris treatment. Identical quantities were applied as early increments (0, 3, and 6 days) and as delayed increments (0, 15, and 30 days). Other treatments supplied 1/3 plus 2/3 of the standard dose at 0 and 30 days, respectively, and in the reverse order of 2/3 plus 1/3. Early or delayed increments did not increase juice quality, but significantly increased juice yield over that obtained with a single dose. Juice yield was further increased by withholding 213 of the standard dose for 30 days. Yield improvement is traced to an alleviation of growth and canopy-development restrictions imposed by the standard Polaris treatment. These responses are interpreted in terms of discrete qualitative and growth-regulatory roles of Polaris, in which growth repression continues to intensify at ripener levels in excess of those needed to attain optimal quality.