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Understanding latitudinal adaptation of switchgrass (Panicum virgatum L.) and Miscanthus (Miscanthus× giganteus J. M. Greef & Deuter ex Hodk. & Renvoize) to the southern Great Plains is key to maximizing productivity by matching each grass variety to its optimal production environment. The objectives of this study were: (1) to quantify latitudinal variation in production of representative upland switchgrass ecotypes (Blackwell, Cave-in-Rock, and Shawnee), lowland switchgrass ecotypes (Alamo, Kanlow), and Miscanthus in the southern half of the US Great Plains and (2) to investigate the environmental factors affecting yield variation. Leaf area and yield were measured on plots at 10 locations in Missouri, Arkansas, Oklahoma, and Texas. More cold winter days led to decreased subsequent Alamo switchgrass yields and increased subsequent upland switchgrass yields. More hot-growing season days led to decreased Kanlow and Miscanthus yields. Increased drought intensity also contributed to decreased Miscanthus yields. Alamo Electronic supplementary material The online version of this article

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Core Ideas Two‐year study evaluating high biomass sorghum yield response to a broad range of N treatments. A minimal N fertilizer rate of 56 kg ha−1 is needed to increase average ethanol yield to 5519 L ha−1, with no additional yield benefit at greater N rates. Yields were limited by varying environmental conditions and delayed planting. Nitrogen recovery efficiency were greatest at low N rates, but N use efficiency more stable across N rates, but greatly impacted by environment. High biomass sorghum [Sorghum bicolor (L.) Moench] could potentially produce high yields in the midwestern United States with minimal fertilizer inputs. However, little is known about the yield response, N uptake, nitrogen use efficiency (NUE), and nitrogen recovery efficiency (NRE) of high biomass sorghum (HBS) at varying N fertilization rates when grown for lignocellulosic ethanol. The objectives of this 2‐yr study were to determine the effect of five N rates (0, 56, 112, 168, 224 kg N ha−1) on the dry matter (DM) yield and lignocellulosic ethanol yield (LEY), and the NRE and NUE of two HBS varieties in the midwestern United States. The two varieties responded similarly for most measured parameters. Total DM yield averaged 13.1 Mg ha−1 and estimated LEY averaged 5519 L ha−1 across N rates when grown in central Missouri. Nitrogen rates between 56 and 224 kg N ha−1 resulted in similar DM yield and LEY in 2010, and there were no yield differences among N rates ranging from 0 to 224 kg N ha−1 in 2011. The greatest N removal in DM was at or above 56 kg N ha−1. Nitrogen recovery efficiency and NUE differed by year, where low rainfall and a shortened growing season in the second year resulted in reduced NRE and NUE. Lack of NUE and DM yield differences at N rates above 56 kg N ha−1 indicates the potential for producing high biomass sorghum with minimal amounts of fertilizer N in the Midwest.

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Recently, sweet sorghum [Sorghum bicolor (L) Moench] has garnered renewed attention as a promising feedstock for ethanol production. A byproduct of this is bagasse, which is sweet sorghum stalks remaining after juice extraction. It is possible that sweet sorghum bagasse could provide a source of livestock feed and that its nutritive value could be increased by ammoniation. Ammoniation refers to the treatment of low‐quality forages with NH3 to improve crude protein concentration, digestibility, and animal intake. The main objective of this study was to evaluate sweet sorghum bagasse as a livestock feed and determine the effect of ammoniation on in vitro true digestibility (IVTD) and crude protein (CP) of sweet sorghum bagasse. In vitro true digestibility and CP were determined on bagasse of 12 sweet sorghum cultivars grown in three environments and treated with and without anhydrous NH3 (39.0 g kg−1). Across environments, ammoniation increased bagasse IVTD from a mean of 731 g kg−1 dry matter (DM) to a mean of 750 g kg−1 DM, but IVTD of bagasse from only two of three environments was increased. Crude protein averaged 117 g kg−1 DM for ammoniated samples compared to 26 g kg−1 DM for nontreated samples. Ammoniation increased CP in every cultivar and in every environment. Sweet sorghum bagasse IVTD and CP characteristics combined with large yields indicate that this byproduct could serve as livestock feed and merits further investigation.

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