Response of Application of Growth Inhibitors on Sugarcane Productivity and Sucrose Accumulation in the Middle of Cropping Season in Brazil

The technical and agricultural planning of sugarcane crops has been crucial to ensure that high-quality millable cane is supplied to the sugar and alcohol industry. This study aimed to evaluate sugarcane development, sucrose accumulation (pol cane), stalk productivity, invertase activity, and ratoon regrowth with the application of plant regulators of the growth inhibitors class [sulfometuron methyl, glyphosate, and compounds from organic carboxylic radicals (C.C.) + glyphosate] for two consecutive years in the middle of the cropping season in Brazil. The treatment with plant regulators made positive influence on the technological quality of millable cane, mainly with regard to increase in the pol content. In weather conditions unfavorable to ripening, the plant regulators sulfometuron methyl and glyphosate were more efficient in increasing the sucrose content than C.C. + glyphosate and control treatments. A positive correlation was also recorded between climate conditions and invertases activity levels, mainly for the neutral invertase (NI). The NI levels under favorable weather conditions to natural ripeness were reported higher than unfavorable conditions to natural ripeness. Sulfometuron methyl increased soluble acid invertase (SAI) and NI activity levels of the sugarcane juice under unfavorable weather condition for ripening while glyphosate applied alone or in association with compounds from organic carboxylic radicals do not change of activity of enzymes. The C.C. + glyphosate and control treatments provided increase in the stalk productivity, while glyphosate reduced the yield. The plant regulators did not affect sugarcane ratoon regrowth.