Trend of Soil and Leaf Potassium Content of Sugarcane: Impact of Soil Type, Fertilizer Source and Application Timing.

Increasing fertilizer use efficiency can be achieved by matching nutrient supply with plants’ demand and maintaining nutrient availability throughout their critical growth stages. A field experiment was established in 2015 at LSU AgCenter Sugar Research Station in St. Gabriel, Louisiana to monitor the changes in soil and leaf K at different critical growth stages of sugarcane (Saccharum officinarum) grown on a light and heavy-texture soil. The experiment was set at two different sites with a total of 18 treatments, arranged in randomized complete block design on a Sharkey clay and complete randomize design on a Commerce silt loam soil with four replications. For this study, data were collected from selected plots only: control, and those treated with 90 Kg K ha^-1 as muriate of potash (MOP, 60% K) and 45 Kg K ha^-1 as MOP + 45 Kg K ha^-1 as a controlled release polymer coated K (Agrocote KCl®, 51%) for both application timing (March and April). Sixteen cores soil samples were collected every two weeks (following March application) from each treatment plot at two depths (0 -15 and 15 - 30 cm) in both sites, oven dried at 60^oC for three days, processed and analyzed for K using Mehlich-3 procedure. Four weeks later (following March application), eighteen leaf samples were collected from each treatment plot every two weeks, oven dried at 60^oC, processed and digested using HNO₃-H₂O₂ digestion procedure followed by ICP spectrophotometry for total K.