Rhizoma peanut responses to harvest frequency and nitrogen fertilization on Louisiana Coastal Plain soils

Despite limitations in stand establishment, rhizoma peanut (Arachis glabrata Benth.) is the only sustainable, productive, high-quality, perennial, warm-season legume available for the Coastal Plain of the lower Gulf Coast Region. Management to enhance productivity could increase acceptance of this relatively unexploited forage. Yield responses of rhizoma peanut to harvest frequency and N fertilization on Louisiana Coastal Plain soils were evaluated. Nitrogen rates of 0, 85, and 170 kg ha^-1 were applied to a Dexter loam soil (Ultic Hapludalfs) in a greenhouse experiment. At three field locations, N rates were 0, 110, and 220 kg ha^-1 and harvest frequencies were 30 and 60 d. Soils were the Dexter loam, Tangi silt loam (Typic Fragiuduits), and Bowie fine sandy loam (Plinthic Paleudults). In the greenhouse, N accumulated in herbage (30 g kg^-1 with 170 kg N ha^-1 vs. 20 g kg^-1 for the control) with a subsequent linear yield increase. In the field, the only responses to N fertilizer were small increases in N concentration of rhizomes plus stubble. Interactions of harvest frequency and location on herbage yield indicated effects of weather. This effect is illustrated by the 790 kg ha^-1 advantage of the 30-d harvest frequency on the Tangi silt loam in May-June vs. the 1930 kg ha^-1 advantage of the 60-d harvest frequency on the Bowie fine sandy loam in July-August. Thus, on the Louisiana Coastal Plain, yield of rhizoma peanut is not likely to be increased by N fertilization, and harvest frequency or length of regrowth period is not a reliable determinant of yield.