Synopsis Oats and Italian ryegrass accumulate large quantities of nitrate but permanent pasture grasses and legumes do not. Oat stems contained more nitrate than leaves. Winter forages following summer clean fallow contained more nitrate than those following weeds. Time of season, daily low temperatures, and variations between daily low and high temperatures also affected nitrate contents.

No abstract

‘Greenalta’, ‘Redalta’, and particularly ‘Bigalta’ limpograsses [Hemarthria altissima (Pior.) Stapf and Hubbard] have been commercially planted in south Florida during the past decade. Since little information is available on agronomic attributes of limpograss during the cool‐season when tropical grass growth is markedly reduced, cool‐season productivity and in vitro organic matter digestibility (IVOMD) were compared with other commercial tropical grasses adapted to south Florida. Effects of nitrogen rates, cutting interval, and fall fertilization dates also were determined for Bigalta to provide information on productivity and IVOMD. The soil used was an Oldsmar fs, a spodosol. The three limpograss cultivars, ‘Transvala’ digitgrass (Digitaria decumbens Stent.), and ‘Coastcross‐1’ bermudagrass (Cynodon sp.) were equally productive during the cool season and more productive than ‘Pangola’ digitgrass (Digitaria decumbens Stent.), Bigalta IVOMD generally was greater than that of Greenalta and particularly Redalta, equal to that of Transvala and Pangola, and higher than that of Coastcross‐1. Dry matter yields of Bigalta, Coastcross‐1‐ and Transvala were similar at 3 or 4‐week cutting intervals (CI), but Bigalta produced less at a 2‐week CI. During a 24‐week period as CI increased from 4 to 12 weeks (total of 336 kg N/ha applied), Bigalta total yields increased, forage IVOMD and N contents decreased, and yield of digestible organic matter increased. Delaying fall fertilization from 17 September or 1 October until 29 October resulted in greatly reduced forage production when harvested on 17 December. The IVOMD and N contents increased as fertilization was delayed. Many of the N contents from the fertilization date and CI studies were below the acceptable level for maximum voluntary intake of forage by ruminants. Productivity of the limpograsses and Bigalta response to N during the cool season indicate that they offer alternatives to other commercially available tropical grasses. The high digestibility of Bigalta can provide reserve coolseason pasture with quality equal to or better than that from other grasses, however, low N contents may limit intake without proper grass management and N fertilization.

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The potential N contribution of tropical legumes to grass pastures on the infertile soils of Peninsular Florida necessitates increased efforts to develop suitable pasture legumes. Nineteen accessions representing 17 tropical legume species were evaluated for persistence under grazing in bahiagrass swards on a Peninsular Florida Arenic Haplaquod (Spodosol) soil. After three growing seasons in the mixed grass‐legume swards, only Vigna parkeri Bak. and aeschynomene (Aeschynomene americana L.) covered larger areas than were originally planted. Indications of potential adaptation to flatwoods pastures were also obtained with ‘Florida’ carpon desmodium [Desmodium heterocarpon (L.) DC], phasey bean [Macroptilium lathyroides (L.) Urb.], Vigna adenantha (G.F. Meyer) Marechal, Mascherpa, and Stainier and Vigna luteola (Jacq.) Benth. However, the variation in response of these four accessions among field replications indicates that site and management requirements of these legumes need further investigation.