No abstract

Florida dairies need year-round forage systems that prevent loss of N to ground water from waste effluent sprayfields. Our purpose was to quantify forage N removal and monitor nitrate N (NO3(-)-N) concentrations in soil water below the rooting zone for two forage systems during four 12-mo cycles (1996-2000). Soil in the sprayfield is an excessively drained Kershaw sand (thermic, uncoated Typic Quartzipsamment). Over four cycles, average loading rates of effluent N were 500, 690, and 910 kg ha(-1) per cycle. Nitrogen removed by the bermudagrass (Cynodon spp.)-rye (Secale cereale L.) system (BR) during the first three cycles was 465 kg ha(-1) per cycle for the low loading rate, 528 kg ha(-1) for the medium rate, and 585 kg ha(-1) for the high. For the corn (Zea mays L.)-forage sorghum [Sorghum bicolor (L.) Moench]-rye system (CSR), N removals were 320 kg ha(-1) per cycle for the low rate, 327 kg ha(-1) for the medium, and 378 kg ha(-1) for the high. The higher N removals for BR were attributed to higher N concentration in bermudagrass (18.1-24.2 g kg(-1)) than in corn and forage sorghum (10.3-14.7 g kg(-1)). Dry matter yield declined in the fourth cycle for bermudagrass but N removal continued to be higher for BR than CSR. The BR system was much more effective at preventing NO3(-)-N leaching. For CSR, NO3(-)-N levels in soil water (1.5 m below surface) increased steeply during the period between the harvest of one forage and canopy dosure of the next. Overall, the BR system was better than CSR at removing N from the soil and maintaining low NO3(-)-N concentrations below the rooting zone.

Arblick (Reg. No. GP‐128; PI 658528) and Ecoturf (Reg. No. GP‐129; PI 658529) are rhizoma peanut (RP) (Arachis glabrata Benth.) germplasms released by the Univ. of Florida in 2008. These plant introductions were identified as lower growing “ground cover” type plants. These lines are being released as germplasm to document the dual purpose ornamental and forage characteristics of the lines. Arblick was collected near the town of Bela Vista, Brazil, located on the border of Brazil and Paraguay. It has green group leaves (RHS 137B), with an orange group standard petal (RHS 24A and a yellow orange group wing petal (RHS 14B). Arblick generally is somewhat slower to establish than other forage type cultivars, has limited forage potential, and has not been widely planted. Ecoturf was collected along the Brazil–Paraguay border on the same collection expedition as Arblick, not far from where Arblick was collected. Flower color of Ecoturf is similar to Arblick, but it has yellow green group leaves (RHS 144A). Arblick and Ecoturf are lower growing types that flower profusely during the growing season. Ecoturf has gained acceptance by the commercial landscape industry for use as an ornamental ground cover. These germplasms will benefit specialty users of “ornamental” types of RP but also because of their dual‐use potential will diversify the RP plantings to avoid the near monoculture of ‘Florigraze’

‘Florigraze’ rhizoma perennial peanut (RPP; Arachis glabrata Benth.) is a high‐quality forage legume vegetatively propagated by rhizomes. The impact of prior RPP defoliation management on rhizome chemical composition and growth after planting is not understood. These two studies, conducted on a Gressarenic Paleudult soil, evaluated the effects of grazing on (i) rhizome mass, total nonstructural carbohydrate (TNC), and N concentration, and (ii) rhizome establishment performance following planting. Rhizomes for both studies were obtained from pastures previously grazed at different combinations of rest interval length (d) and quantity of residual dry matter remaining after grazing (kg ha−1). Specific rest interval‐residual dry matter combiuatious (21‐500, 63‐500, 42‐1500, and 63‐2500) were chosen to represent a wide range of grazing severity. An ungrazed treatment (No‐Grz) was also included. Average rhizome mass was greatest (17.0 Mg ha−1) for No‐Grz and declined as grazing severity increased from 63‐2500 (9.4 Mg ha−1) to 21‐500 (2.3 Mg ha−1). Grazing treatments also provided rhizome planting material with a wide range of TNC concentration (62‐301 g kg−1) and N concentration (12.7‐22.1 g kg−1 Greatest concentrations were observed for No‐Grz and less severely grazed pastures. Planting rhizomes with initial TNC ≥ 228 g kg−1 and N ≥ 20 g kg−1 resulted in the greatest seasonal accumulation of both rhizome and shoot mass. Planting rhizomes with low TNC (62 kg−1; 21‐500) resulted in stand failure in a drought year (1990). Rhizomes with higher TNC (139 g kg−1; 63‐500) produced shoots that survived drought conditions but growth rates were relatively slow. We conclude that grazing affects chemical composition of RPP rhizomes and that chemical composition of planting material is a major determinant of RPP establishment success.

‘UF Tito’ (Reg. No. CV‐107, PI 262826) and ‘UF Peace’ (Reg. No. CV‐108, PI 658214) rhizoma perennial peanut (RP; Arachis glabrata Benth.) cultivars were released by the University of Florida in 2008. After introduction into the United States in 1936 from Brazil, evaluations showed RP to be well adapted to the U.S. Gulf Coastal Plains region. UF Tito originated from Paraguay and was collected in 1959. This plant introduction resembles the plant type of ‘Florigraze’. It was identified as having high dry matter yields, highest percent pure peanut, and greatest vigor based on the amount of spread in a 10‐yr evaluation experiment. In subsequent multilocation experiments over a 5‐yr period, yields were generally equal to or higher than Florigraze. UF Peace was received in Florida in 1986 from Charles Simpson at the Texas AgriLife Research Center at Stephenville, TX, as collection no. P‐2352. The ID numbers when the material was received trace it to PI 262839, an introduction subsequently released as the germplasm Arblick. Amplified fragment length polymorphism evaluation indicates that the molecular profile of this line is different from Arblick and all other known A. glabrata germplasm. It resembles the plant type of Florigraze, and its dry matter yields and competitiveness with weedy bermudagrass [Cynodon dactylon (L.) Pers.] are comparable. UF Peace appears to have better adaptability to the upper Coastal Plains. Both cultivars show improved field tolerance to peanut stunt virus compared with Florigraze.