Effect of CaSiO3 Slag Rates and Application Time on Sugarcane Yield and Soil Silicon and Plant-Essential Nutrient Content.

In Louisiana sugarcane production system, soil amendments like CaSiO₃ slag (Si source) is applied at large rates once, before planting. Annual spring application of CaSiO₃ slag at lower and manageable rates with other granular fertilizer can facilitate the adoption of this rather new agronomic practice in sugarcane production. This study was conducted to evaluate the effect of CaSiO₃ slag applied at different rates and time, on soil nutrients availability, including Si, and sugarcane yield in a 3-year cropping cycle. Treatments included CaSiO₃ slag applied either once at planting  at 4.5 MT ha^-1, split at planting and annual spring application (1.1 + 1.1 and 2.25 + 1.1 MT ha^-1), or only in spring, annually (0.6, 1.1, 1.7, and 2.25 MT ha^-1). For plant cane, the application of 1.1 MT CaSiO₃ slag ha^-1 at planting or in spring tended to obtain the largest amount of millable stalks. The largest increase in pH and soil Si was achieved by the application of 4.5 MT CaSiO₃ slag ha^-1 at planting and spring application at rates of 1.1, 1.7 and 2.25 MT ha^-1. For ratoon cane, the annual application of 1.7 MT CaSiO₃ slag ha^-1 in spring resulted in the highest sugar yield, what can be partly attributed to higher amount of millable stalks produced (P<0.05). There was an evident increased in soil Si across rates and time of application of CaSiO₃ compared to control plots. Only soil magnesium content based on Mehlich-3 procedure was increased while calcium and zinc tended to increase with increasing application rate wherein higher level were observed in response to the annual application. Our findings demonstrate the potential of annual application of CaSiO₃ at modest rates as an alternative to traditional large application rate at planting in sugarcane production system.