Silicon and Nitrogen Fertilization Influences Wheat Biomass and Grain Yield.

Silicon (Si) fertilization has been documented beneficial to numerous crops but there has been little research published to show the effect of both Si and nitrogen (N) fertilization in wheat (Triticum aestivum L.) production. A field study was established in 2012 on a Commerce silt loam soil in Northeast Louisiana to evaluate the interactive effects of Si and N on wheat biomass and grain yield, and establish the Si application rate to maximize wheat grain yield. The treatments consisted of two N rates (101 and 145 kg ha^-1) combined with four calcium silicate slag (CaSiO₃, 17% Si) rates of 1, 2, 4.5, and 9 Mt ha^-1 with four replications arranged in a randomized complete block design. Each replication contained two check plots, neither of which received any N or Si fertilization. One of the check plots was applied with lime (CaCO₃, 90% Calcium Carbonate Equivalent) at 4.5 Mt ha^-1. Biomass clippings and canopy height measurements were taken at Feekes 5 and 10.5 growth stages while at harvest plot yield and yield components were collected. Soil samples collected at post-harvest were extracted using 0.5 M acetic acid solution and analyzed for Si concentration by Molybdenum Blue Colorimetry. Mean grain yield of the plots treated with 101 kg N ha^-1 was 402 kg ha^-1 higher than those fertilized with 145 kg N ha^-1 (P<0.10). The addition of CaSiO₃ slag at a rate of 4.5 Mt ha^-1  tended to increase grain yield of plots supplied with 145 kg N ha^-1 while in plots applied with 101 kg N ha^-1,  the highest grain yield was obtained at 2 Mt CaSiO₃ slag ha^-1 application rate. On average, the application of 4.5 Mt ha^-1 of CaSiO₃ slag raised the 0.5 M acetic acid extractable Si by 48 mg kg^-1. There were indications of Si and N interaction effect on wheat growth and development. The resulting increase in yield due to CaSiO₃ slag application was more evident when combined with optimal N application rate. Replicates of this study will be conducted in several site years to support these initial findings.