Growth Characteristics of Rhizoma Peanut and Nitrogen-Fertilized Bahiagrass Swards
The interaction of plant sensitivity to drought with N deficiency has been suggested as the reason grasses fail to persist under grazing when grown in association with rhizoma peanut (Arachis glabrata Benth.). To test this assumption, aboveground dry matter (DM) accumulation and relative growth rate (RGR) of ‘Florigraze‘ rhizoma peanut and ‘Pensacola’ bahiagrass (Paspalum notatum Flügge) fertilized with 0, 56, and 112 kg N ha−1 were measured from March to November in 1990 and 1991. Rhizoma peanut aboveground DM accumulation was greater both years (4950 and 6100 kg ha−1 1990 and 1991, respectively) in July at the start of the summer rainy season than any N-fertilized bahiagrass treatment (640 and 1530, 1240 and 2330, and 1570 and 4490 kg ha−1 in 1990 and 1991 for 0-N, 56-N, and 112-N treatments, respectively), due to higher RGR. Although the RGR of rhizoma peanut was similar to or less than that of the bahiagrass treatments for the remainder of the growing season in both years, by August 1991 only the 112-N bahiagrass treatment (5260 kg ha−1) had total DM accumulation similar to rhizoma peanut (5110 kg ha−1). Rhizoma peanut RGR appeared to be more sensitive to rainfall, and was positively correlated (r = 0.71) with rainfall for as long as 8 wk prior to the sample dates in the dry spring of 1990. Bahiagrass RGR showed no correlation with rainfall either year. This suggests that lack of persistence of bahiagrass in mixed swards is due to severe competition for light with rhizoma peanut in springs when moisture is adequate and to potentially increased stress due to grazing in springs when drought restricts growth of rhizoma peanut.
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