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Establishing vegetation on roadsides following construction can be challenging, especially for relatively slow growing native species. Topsoil is generally removed during construction, and the surface soil following construction ("cut-slope soils") is often compacted and low in nutrients, providing poor growing conditions for vegetation. Nebraska Department of Transportation (NDOT) protocols have historically called for nitrogen (N) and phosphorus (P) fertilization when planting roadside vegetation following construction, but these recommendations were developed for cool-season grass plantings and most current plantings use slower-establishing, native warm-season grasses that may benefit less than expected from current planting protocols. We evaluated the effects of nitrogen and phosphorus fertilization, and also topsoil amendment, on the foliar cover of seeded and non-seeded species planted into two post-construction roadside sites in eastern Nebraska. We also examined soil movement to determine how planting protocols and plant growth may affect erosion potential. Three years after planting, we found no consistent effects of N or P fertilization on foliar cover. Plots receiving topsoil amendment had 14% greater cover of warm-season grasses, 10% greater total foliar cover, and 4-13% lower bare ground (depending on site) than plots without topsoil. None of the treatments consistently affected soil movement. We recommend that NDOT change their protocols to remove N and P fertilization and focus on stockpiling and spreading topsoil following construction.

Understanding leaf generation dynamics, their seasonal changes, and their responses to nitrogen fertilization (NF) is key to improving pasture utilization efficiency. The objectives of this research were to determine structural and morphogenetic variables underlying changes in herbage mass on a set of Paspalum notatum genotypes. Ten P. notatum genotypes were evaluated in experimental plots following a completely randomized block design under a split-plot arrangement for two N-rates during four periods. Increased herbage mass (HM) after N-fertilization was explained by a higher tiller density (TD) (41.8%) and tiller weight (TW) (22.1%). The increment of TW after NF was due to the increase in leaf blade length (LBL) and width (LBW). During the flowering season, NF increases the reproductive tiller density by 262.5%. Seasonal variation in HM was mainly explained by changes in LBL that modified TW. Morphogenetic traits differed between genotypes of different growth habits; therefore, different management practices are suggested. The average increase in leaf elongation rate in response to NF was about 36.7%, generating longer leaves despite reductions in leaf elongation time (LET). The depletion in LBL and consequently in TW and HM during the autumn was attributed to the reduction in LET. [ABSTRACT FROM AUTHOR]

Abstract: The objectives of this research were to determine the effect of N levels and plant maturity on the nutritive quality of four warm-season grasses, and to evaluate relationships between forage quality and morphological development. Indiangrass (Sorghastrum mutans L. Nash), big bluestem (Andropogon gerardii Vitman), Eastern gamagrass (Tripsacum dactyloides L.), and switchgrass (Panicum virgatum L.) were grown in four replications, applied with 3N levels (0, 65, and 140kg/ha), and harvested on ten dates at approximately 2-week intervals for first seven harvest dates and 3-week intervals for last three harvest dates. For all species, harvesting at early maturity increased (P<0.05) forage quality including increased in vitro dry matter digestibility (IVDMD) and crude protein (CP), and decreases in neutral detergent fiber (aNDF) concentrations, whereas allowing forage to reach later maturity reduced forage quality with declines in IVDMD and CP and increases in aNDF concentration. The aNDF concentration in warm-season grasses with the exception of big bluestem increased with N fertilization at 65kg/ha, while N fertilization at 140kg/ha had no consistent effect on aNDF concentration of the four grass species across both years. Nitrogen fertilization increased (P<0.05) the IVDMD value across four grass species in 2006, whereas it decreased (P<0.05) the IVDMD value for switchgrass and did not affect (P>0.05) the IVDMD value for the other three species in 2007. The concentration of CP for all four warm-season grass species increased (P<0.05) at higher rates of N fertilization. Therefore, although there were variations in the effect of N fertilization on aNDF and IVDMD making drawing conclusions difficult, N fertilization could improve forage quality for warm-season grasses through increasing the concentration of CP. For big bluestem, switchgrass, and indiangrass, forage quality parameters showed a quadratic relationship to mean stage by count (MSC), with coefficients of determination ≥0.96 for IVDMD, 0.88 for aNDF, and 0.88 for CP, respectively. However, predicting forage quality changes based on MSC did not provide reasonable estimates (P>0.05) for eastern gamagrass. [Copyright &y& Elsevier]