Calcium Silicate Slag Application Influences Nutrient Availability in Soil and Uptake By Wheat.

The application of calcium silicate (CaSiO₃) slag not only raises plant-available silicon (Si) but also can alter availability of essential nutrients in the soil because of its high liming potential.  This study was conducted from 2012 to 2014 to document the effects of CaSiO₃ slag application on nutrient availability in soil and uptake by wheat. Treatments were arranged in a randomized complete block design with four replications at two fields in St. Joseph and one in Ben Hur Farm, Louisiana. Each replication consisted of two checks: no nitrogen (N) and Si applied, and a lime treatment at 4.5 Mt ha^-1. Two N rates (101 and 145 kg ha^-1) were applied as urea (46% N) and for each N rate, there were five CaSiO₃ slag application rates equivalent to 0, 120, 240, 540, and 1080 kg Si ha^-1. Soil samples taken at midseason and harvest were analyzed for 0.5 M acetic acid extractable Si, Mehlich-3 extractable nutrients, and soil pH. The results showed that application of CaSiO₃ slag increased the content of extractable calcium (Ca), magnesium (Mg), sulphur (S), zinc (Zn), NO₃ (Nitrate) and Si in soil (P<0.05). Straw Si and manganese (Mn) content (and uptake) had a consistent negative relationship for all three site-years (P<0.05). Increasing CaSiO₃ slag rates significantly increased iron (Fe), molybdenum (Mo), phosphorus (P), and S uptake in straw (P<0.05). The application of CaSiO₃ slag increased soil pH across site-years (P<0.01).  Silicon applied at 540 kg ha^-1 resulted in yield increase of 13.7% but only in one site-year. The increased availability of nutrients in the soil and their uptake could play a role in improved yields thus, CaSiO₃ slag as a liming material in place of common agricultural lime may be recommended for sustaining wheat productivity.