Sulfur Fertilization in Louisiana Sugarcane Production Systems.

Sulfur (S) plays an important role in plant metabolism, and is required in photosynthesis and production of amino acids and proteins. The atmospheric S deposition has declined since the implementation of Clean Air Act in 1985 which partially contributes to increasing number of cases of S deficiencies in crop production in the US. Sugarcane exhibits luxury consumption and removes a considerable quantity of S from the soil. Based on previous works, cane stalk S content ranged from 50 to 90 g kg^-1. A 90 ton millable stalk yield ha^-1 can remove as much as 20 kg S. Replicated field experiments were conducted in 2017 at the LSU AgCenter Sugar Research Station in St. Gabriel and Donaldsonville, Louisiana to evaluate the impact of S fertilization using different sources on Louisiana sugarcane production system. The experiment was arranged in a randomized complete block design with four replications. Treatments included ammonium sulfate, ammonium thiosulfate, and a micronized elemental S source (MST, Sulvaris®) plus a control (no S). Soil and leaf tissue samples were collected one month after fertilization and analyzed for S content. The application of S increased leaf S content by 0.03% (30 g kg^-1 leaf dry weight) across the four sites. In Donaldsonville, the highest leaf S content of 0.21% was obtained from plots treated with a source containing both elemental sulfur and sulfate form (Microessentials®). The S content of soil based on Mehlich-3 procedure was higher in plots which received S fertilizers (11 mg kg^-1) than in the control plot (8 mg kg^-1) with Microessentials and liquid MST-treated plots (13 mg kg^-1) having the highest soil S. Our initial results showed that S sources containing sulfate and MST were effective in raising leaf and soil S. A season-long availability of S is important for crops especially for sugarcane which has a long growing season in Louisiana.