Studies into Potassium Management for Sugarcane Production in Northeast Thailand Based on Factory Juice Analysis Combined with Cultivation Experiment

Potassium (K) is one of the essential nutrients for plants; nevertheless, it has been reported that overdoses of K fertilizer have resulted in impaired sugarcane juice quality and a reduction in the efficiency of sugar processing. Therefore, to maximize sugar production per unit area, K levels in sugarcane should be kept just adequate. The aim of this study was to propose a practical method of K fertilizer management based on the nutritional status of sugarcane juice. First, we conducted a pot experiment treating sugarcane with different K fertilizers (potassium chloride, KCl and potassium sulfate, K2SO4) and K rates (0, 2, 10, 30, and 50 g pot-1). Raising KCl rates caused considerably negative impacts on not only the quality but the yield as juice K concentration exceeded 2000 mg L-1, whereas the effects of the K2SO4 treatments were less severe. Second, we collected sugarcane juice at a raw sugar factory over 2 years. Because of its ease of measurement, electrical conductivity was used to deduce juice K concentration. The juice analysis revealed that more than 60% of the samples possessed K concentrations higher than 2000 mg L-1, and the relationship between juice K and sugarcane quality was significantly negative. These results indicate that impairments of sugarcane quality have probably been occurring in the actual fields. Given that sugarcane is generally fertilized with KCl, reducing K fertilizer dose should contribute to improving sugarcane quality and accordingly sugar yield when juice K is considered high.