The Influence of Potassium on the Yield and Sucrose Content of Sugarcane

Abstract

Critical analysis of the results of over 200 field experiments with potash fertilizers on sugarcane conducted by the Agricultural Experiment Station of the University of Puerto Rico, covering a wide ranges of cane varieties and sons types of Puerto Rico, revealed the following: (1) Potash increased cane yields mainly on the red and yellow podzolic soils of the humid area and on a planosol of the semiarid area. There was slight, if any, response to potash in the irrigated area. (2) The use of potash increased the sucrose concentration of the cane only if cane yields were also increased. Increases of 10 percent or more in tonnage were required if increases in sucrose content were to be expected. A linear relation Y = 0.12 x + 0.55 was obtained where Y was the percentage increase in sucrose-percent-cane and x the percentage increase in tons of cane yielded per acre. (3) When potash fertilizers significantly influenced the sucrose concentration of the cane, the polarization value of the cane juice increased. Brix and percentage extractability of juice were not appreciably affected. (4) The use of foliar diagnosis has proven to be of great value in Puerto Rico in determining when to apply potash fertilizers to sugarcane. Leaf values of 2 percent or more, on a dry-weight basis, indicate that no response to potash applications can be expected for soils and varieties in Puerto Rico. Values below 1.80 percent indicate that a response to potash fertilizers may be expected in the humid areas.