Impact of Silicate Slag Fertilization on Wheat Yield and Grain Protein Content.

Silicon (Si) accumulates as dehydrated silica in leaves and stems which contributes to plants’ mechanical strength and more upright canopy structure; the latter is believed to facilitate efficient light interception within plant canopy and nitrogen (N) use. Wheat is a Si accumulator with an average of 2.5% Si content in dry biomass. This study was conducted to evaluate the effect of silicate slag application on yield and grain protein content of wheat in Louisiana production system.  Yield, grain N content, and soil Si data were collected from 10 wheat trials conducted from 2013 to 2016 at different locations in Louisiana. Plots in these trials were treated with varying rates of silicate slag (12% Si) and N applied as urea (46%N), arranged in randomized complete block design with four replications. Dried, ground grain samples were analyzed for N content using CN dry combustion analyzer; protein content of grain was computed by multiplying %N of grain with 5.83. Soil Si was determined using 0.5 M acetic acid extraction procedure followed by molybdenum blue colorimetry. Analysis of variance on yield, protein content, and soil Si was performed for each site-year. Regression analysis was conducted for soil Si and grain protein content data pooled across site-years. Grain protein content was significantly increased from 10 to 11% with a modest application rate of 1 ton ha^-1 of silicate slag (P<0.05). In other site-year, higher application rate (7 tons ha^-1) was required to attain similar increase in grain protein. On average, grain yield was increased by 12% between the application rates of 2 to 4 tons silicate slag ha^-1 (P<0.05). Notable increases in soil Si with increasing silicate slag application were observed across site-years (P<0.001).