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Napier grass (Pennisetum purpureum Schumach) has been identified as a potential energy crop in Thailand. However, information regarding the biomass production characteristics of napier grass in response to K and N fertilization is required to guide management decisions for biofuel feedstock. Our objective was to determine the effects of K and N rates on biomass yield, developmental morphology, nutrient content and removal. This experiment was conducted during 2016 and 2017 at Kamphaeng Saen (KPS), Thailand. The experimental design was a split plot arranged in a randomized complete block (RCB) with four replications. Three K fertilization rates (0, 250, and 500 kg ha−1) were used for the main plots and four N fertilization rates (0, 250, 500, and 1000 kg ha−1) were arranged as subplots. With increasing N fertilization rate, most growth parameters increased, except leaf to stem ratio and dry matter concentration decreased. Total dry matter yield (TDMY) increased from 16.6 to 43.0 t ha−1 and from 15.2 to 41.6 t ha−1 in 2016 and 2017, respectively, as N rate increased from 0 to 1000 kg ha−1. However, growth and TDMY were not affected by K fertilizer. Increased TDMY resulted from an increase in the proportion of elongating tillers leading to advancing mean stage by count (MSC) from 2.35 to 2.45. Therefore, although napier grass demonstrated large biomass production under multiple harvest regimes, its higher removal rates (285.0–1615. kg K ha−1 and 86.7–422.2 kg N ha−1) were varied with fertilization rates indicating a potential for higher fertilizer requirements and production costs over time. [ABSTRACT FROM AUTHOR]

High yielding, native warm-season grasses could be used as renewable bioenergy feedstocks. The objectives of this study were to determine the effect of warm season grass monocultures and mixtures on yield and chemical characteristics of harvested biomass and to evaluate the effect of initial seeding mixture on botanical composition over time. Switchgrass ( Panicum virgatum L.), indiangrass [ Sorghastrum nutans (L.) Nash], and big bluestem ( Andropogon gerardii Vitman) were planted as monocultures and in all possible two- and three-way mixtures at three USA locations (Brookings and Pierre, SD and Morris, MN) during May 2002. Biomass at each location was harvested after a killing frost once annually from 2003 to 2005. Total biomass yield significantly increased with year at all locations. Switchgrass monocultures or mixtures containing switchgrass generally out-yielded big bluestem or indiangrass in monocultures or the binary mixture. Cellulose and hemicellulose concentrations were higher in 2004 and 2005 compared with 2003. Switchgrass or mixtures containing switchgrass tended to have less cellulose than either big bluestem or indiangrass. Results were more variable for total N, lignin, and ash. Switchgrass was the dominant component of all mixtures in which it was present while big bluestem was dominant when mixed with indiangrass. Indiangrass was maintained only in monocultures and declined over years when grown in mixtures at all locations. Our results indicated if biomass yield in the northern Great Plains is a primary objective, switchgrass should be a component of binary or tertiary mixtures that also contain big bluestem and/or indiangrass. [ABSTRACT FROM AUTHOR]

Perennial grasses may provide a renewable source of biomass for energy production. Biomass yield, nutrient concentrations, and nutrient removal rates of switchgrass ( Panicum virgatum L.), giant miscanthus ( Miscanthus x giganteus), giant reed ( Arundo donax L.), weeping lovegrass [ Eragrostis curvula (Shrad.) Nees], kleingrass ( Panicum coloratum L.), and Johnsongrass ( Sorghum halepense (L.) Pers.) were evaluated at four N fertilizer rates (0, 56, 112, or 168 kg N ha) on a Minco fine sandy loam soil in southern Oklahoma. Species were established in 2008 and harvested for biomass in winter of 2009 and 2010. Biomass yield (dry matter basis) did not show a strong relationship with N fertilizer rate ( p = 0.08), but was affected by year and species interactions ( p < 0.01). Weeping lovegrass and kleingrass produced 29.0 and 16.0 Mg ha in 2009, but only 13.0 Mg ha and 9.8 Mg ha in 2010, respectively. Biomass yields of giant reed, switchgrass, and Johnsongrass averaged 23.3, 17.8, and 6.0 Mg ha, respectively. Giant miscanthus established poorly, producing only 4.7 Mg ha. Across years, giant reed had the highest biomass yield, 33.2 Mg ha at 168 kg N ha, and the highest nutrient concentrations and removal rates (162 to 228 kg N ha, 23 to 25 kg P ha, and 121 to 149 kg K ha) among the grasses. Although giant reed demonstrated tremendous biomass production, its higher nutrient removal rates indicate a potential for increased fertilization requirements over time. Switchgrass had consistently high biomass yields and relatively low nutrient removal rates (40 to 75 kg N ha, 5 to 12 kg P ha, and 44 to 110 kg K ha) across years, demonstrating its merits as a low-input bioenergy crop. [ABSTRACT FROM AUTHOR]

Abstract: Switchgrass (Panicum virgatum L.), big bluestem (Andropogon gerardii Vitman), and indiangrass (Sorghastrum nutans (L.) Nash) are native warm-season grasses commonly used for pasture, hay, and conservation. More recently switchgrass has also been identified as a potential biomass energy crop, but management of mixtures of these species for biomass is not well documented. Therefore, the objectives of our study were to: (1) determine the effects of harvest timing and N rate on yield and biomass characteristics of established warm-season grass stands containing a mixture of switchgrass, big bluestem, and indiangrass, and (2) evaluate the impact of harvest management on species composition. Five N rates (0, 56, 112, and 224kgha−1 applied annually in spring and 224kgha−1 evenly split between spring and fall) and two harvest timings (anthesis and killing frost) were applied to plots at two South Dakota USA locations from 2001 to 2003. Harvesting once a year shortly after a killing frost produced the greatest yields with high concentrations of neutral detergent fiber (NDF), acid detergent fiber (ADF), and acid detergent lignin (ADL) along with lower concentrations of total nitrogen (TN) and ash. This harvest timing also allowed for the greatest percentage of desirable species while maintaining low grass weed percentages. While N rates of 56 and 112kgha−1 tended to increase total biomass without promoting severe invasion of grass and broadleaf weed species, N application did not always result in significant increases in biomass production. Based on these results, mixtures of switchgrass and big bluestem were well suited for sustainable biomass energy production. Furthermore, N requirements of these mixtures were relatively low thus reducing production input costs. [Copyright &y& Elsevier]

We studied the establishment of native warm-season grasses on gravel mine spoils infested by spotted knapweed (Centaurea maculosa), an exotic perennial that is difficult to control on droughty, infertile sites. We applied factorial combinations of sewage sludge (0 and 11.9 Mg ha-1 [5.3 tons ac-1]) and herbicide (none; 2,4-D; and glyphosate) to evaluate their effects on native grass establishment and on competition between native grasses and spotted knapweed. While native grasses were successfully established with all treatment combinations, sludge application reduced their densities. Warm-season grass biomass subsequently increased rapidly on both sludge and control plots. Both herbicide treatments reduced density and biomass of knapweed during the first two years of the study, but glyphosate and sludge interacted to produce increased knapweed biomass during the third year. For this reason, it may be desirable to delay application of sludge amendments until warm-season grasses are well established in herbicide-treated areas. The response of knapweed to improved soil fertility was dependent on the degree of grass competition, and where this remained high, knapweed dominance was suppressed. While warm-season grasses appeared to compete successfully with spotted knapweed, additional control measures may be required to maintain grass dominance on this and similar knapweed-infested sites. [ABSTRACT FROM AUTHOR]