Common bermudagrass [Cynodon dactylon (L.) Pers] is a widely used forage on the shallow, droughty coastal plain in southwest Louisiana. Management inputs including fertilizer are typically minimal, even though common bermudagrass has proven as productive as Coastal bermudagrass on these shallow soils. Lack of information about responsiveness of common bermudagrass to specific fertilizer treatments on these soils has led to an evaluation of sources of nitrogen (N) at two rates of N compared to a zero N control and the high N rate plus magnesium (Mg), sulphur (S), and boron (B). At 224 kg N/ha split into four applications, urea produced only 82% as much (P<0.05) forage as ammonium nitrate. However, at 448 kg N/ha the two sources produced similar yields (P>0.05). Forage production from 448 kg N/ha as ammonium nitrate plus Mg, S, and B was 16% greater (P<0.05) than that from the same rate of ammonium nitrate without Mg, S, and B. Each increment of N produced small but distinct increases in crude protein (CP), decreases in acid detergent fiber (ADF), and increases in in vitro digestibility (IVD). Whether or not to use urea as a source of N on common bermudagrass on these shallow soils appears to be especially pertinent at relatively low N rates. At N rates approaching 450 kg/ha annually, secondary nutrients may limit forage production from common bermudagrass hay fields on shallow coastal plain soils.
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