No abstract

Synopsis Nitrogen fertilization increased the production of Pensacola bahiagrass but did not influence the seasonally of production. Over a 3‐year period total production averaged 12% in April and May, 64% in June and July, and 24% in August and September. Phosphorus content of the forage was very high (0.36%) and averaged 41% higher than the calcium content.

Pensacola bahiagrass (Paspalum notatum Flugge) is normally grown in pure stands and produces forage primarily on stolons growing along the soil surface. Harvesting by clipping has been at a height of 6 to 7 cm and N fertilization has traditionally been in split applications with the first in March or April. Advantages of split applications have not been established and clip ping at 6 to 7 cm may seriously underestimate forage production. More detailed information is needed to accurately establish total forage yields and seasonal forage production patterns under close clipping. A field clip ping investigation was conducted where bahiagrass sod receiving 0, 84, 168, and 336 kg/ha of N fertilizers in one of six time of application combinations was harvested monthly at a height of 0 to 3 mm. The first year, dry forage production increased from 3,042 kg/ha with 0 N, to 6,398 kg/ha with 336 kg/ha of N. In the second year, forage production at the same N rates ranged from 3,812 to 12,151 kg/ha. Close clipping (0 to 3 mm stubble) resulted in different seasonality of forage production and N concentrations when compared to previous results where clipping was at heights of 6 to 7 cm. Increasing the N application rate increased root and stolon weights. Forage production efficiency of applied N (kg dry matter produced/kg N applied) decreased from 54.6 for the first 84 kg/N/ha applied to 34.0 for the additional N from 84 to 168 kg/ha and further to 5.2 for N from 168 to 336 kg/ha N. With unfertilized bahiagrass, N should be applied by or before early March, but after the first year, time of N application makes no practical difference in yield. At low N rates, harvesting to a stubble height of 3 cm or less will significantly increase the amount of forage utilized , harvested, or reduce the amount of N applied. It was concluded that close grazing or clipping of Pensacola bahiagrass wilt: a) increase digestibility by keeping the forage green; b) increase the effective yield of a pasture; and c) split applications of N may provide better forage distribution over a season without affecting yield.

‘Coastal’ bermudagrass was grown on an extremely acid Cecil sandy loam soil in order to study the influence of limestone rate (0, 7,846, and 40,349 kg/ha), limestone placement (surface and mixed), and N levels (0, 224, 448, 896, and 1,793 kg/ha) on forage production, rooting, and changes in soil properties. Without limestone, annual forage production declined with time at the 448‐kg/ha N level and above, and Coastal bermudagrass plants exhibited a severe chlorosis. At the two highest N levels (896 and 1,793 kg/ha), up~o 90% of the plants died. Limestone increased annual forage yields at N rates of 896 kg/ha and above. Mixing the limestone with the surface soil resulted in significantly higher forage yields at the 1,793‐kg/ha level. The movement of Ca and Mg into all soil zones down to the 30‐ to 45‐cm zone confirmed the changes in soil pH. Soil pH was reduced by annual applications of 448 kg/ha of 1N and forage yields of Coastal bermudagrass were severely restricted. Coastal roots penetrated to 120 cm in soil with a range in pH from 4.0 to 4.5, emphasizing the extreme tolerance of this grass to very low soil pH.