Hari P. Singh

Torrefaction of sorghum biomass to improve fuel properties

Torrefaction of energy sorghum and sweet sorghum bagasse was investigated at three different temperatures (250, 275 & 300°C) for 30min to determine product yields and its compositions. The torrefied solid yield ranged from 43% to 65% for sweet sorghum bagasse and 51-70% for energy sorghum. The energy density of both torrefied sorghums increased between 1.6 and 1.4 folds. Besides water, the acetic acid, with a maximum yield of 101.90gL-1 was the dominant compound in the aqueous fraction of liquid products. The aqueous fraction from sweet sorghum bagasse contained furfural and furan carboxyl aldehydes, while ketones and alcohols were dominant from energy sorghum as other key compounds. Phenolic type chemicals and furan derivatives were the major compounds in the oil fraction of the liquid product, accounted up to 58wt%. The condensable liquid products can be further upgraded into high-value platform chemicals.

Cover Crops for Enriching Soil Carbon and Nitrogen Under Bioenergy Sorghum

Soil carbon (C) and nitrogen (N) can be enriched with cover crops under agronomic crops, but little is known about their enrichment under bioenergy crops. Legume (hairy vetch [Vicia villosa Roth]), nonlegume (rye [Secale cereale L.]), a mixture of legume and nonlegume (hairy vetch and rye), and a control with no cover crop were grown in the winter to evaluate their effects on soil organic C (SOC), total N (STN), and nitrate-N (NO3-N) contents under bioenergy Sorghum from 2010 to 2013. Cover crop biomass and C and N contents were greater with vetch/rye mixture than rye and the control. The SOC at 5–15 and 15–30 cm was greater with vetch/rye than other treatments under forage Sorghum and at 0–5 cm and 5–15 cm was greater with vetch/rye and vetch than rye or the control under sweet Sorghum. The STN at 5–15 cm was greater with vetch/rye and the control than rye under forage Sorghum and at 0–5 and 5–15 cm was greater with vetch/rye and rye than the control under sweet Sorghum. Both SOC and STN at all depths increased linearly from 2010 to 2013, regardless of cover crops and Sorghum species. The NO3-N content at all depths varied with cover crops from 2011 to 2013. Bicultural cover crops, such as hairy vetch/rye mixture, have greater potential to sequester C and N than monocultures, such as hairy vetch and rye, or no cover crop due to greater crop residue returned to the soil under bioenergy Sorghum where aboveground biomass is harvested for bioenergy or feedstock.

Soil Carbon and Nitrogen in Response to Perennial Bioenergy Grass, Cover Crop and Nitrogen Fertilization

Abstract Cover crop and nitrogen (N) fertilization may maintain soil organic matter under bioenergy perennial grass where removal of aboveground biomass for feedstock to produce cellulosic ethanol can reduce soil quality. We evaluated the effects of cover crops and N fertilization rates on soil organic carbon (C) (SOC), total N (STN), ammonium N (NH 4 -N), and nitrate N (NO 3 -N) contents at the 0–5, 5–15, and 15–30 cm depths under perennial bioenergy grass from 2010 to 2014 in the southeastern USA. Treatments included unbalanced combinations of perennial bioenergy grass, energy cane ( Saccharum spontaneum L.) or elephant grass ( Pennisetum purpureum Schumach.), cover crop, crimson clover ( Trifolium incarnatum L.), and N fertilization rates (0, 100, and 200 kg N ha −1 ). Cover crop biomass and C and N contents were greater in the treatment of energy cane with cover crop and 100 kg N ha −1 than in the treatment of energy cane and elephant grass. The SOC and STN contents at 0–5 and 5–15 cm were 9%–20% greater in the treatments of elephant grass with cover crop and with or without 100 kg N ha −1 than in most of the other treatments. The soil NO 3 -N content at 0–5 cm was 31%–45% greater in the treatment of energy cane with cover crop and 100 kg N ha −1 than in most of the other treatments. The SOC sequestration increased from 0.1 to 1.0 Mg C ha −1 year −1 and the STN sequestration from 0.03 to 0.11 Mg N ha −1 year −1 from 2010 to 2014 for various treatments and depths. In contrast, the soil NH 4 -N and NO 3 -N contents varied among treatments, depths, and years. Soil C and N storages can be enriched and residual NO 3 -N content can be reduced by using elephant grass with cover crop and with or without N fertilization at a moderate rate.

Insect Incidence and Damage on Pearl Millet (Pennisetum glaucum) Under Various Nitrogen Regimes in Alabama

Abstract Although pearl millet [Pennisetum glaucum (L.) R. Br.; Poales: Poaceae] is grown extensively on 5 continents and is attacked by various insects at all stages of growth and development, little is specifically known of how yields of this important crop are affected by insect herbivory. This study was conducted in north central Alabama to determine insect occurrence on pearl millet and to determine the levels of damage caused by insects feeding on pearl millet genotypes at different nitrogen rates. The field experiment was laid out following a randomized complete block design with 4 replications in which 4 genotypes and 4 fertilizer levels were arranged in factorial combinations. The pearl millet genotypes consisted of 2 open pollinated lines, ‘2304’ and ‘LHBO8’, and 2 hybrids, ‘606A1*2304’ and ‘707A1*4280’ and fertilization rates used were 0, 40, 80 and 120 kg ha-1 N. Insect samplings were carried out weekly from 61 to 109 days after planting (DAP). Insects in 6 orders and 11 families were found on pearl millet genotypes. Eastern leaf-footed stinkbug (Leptoglossus phyllopus (L.); Hemiptera: Coreidae) was the most prevalent and dominant insect species found followed by the American bird grasshopper (Schistocerca americana Drury; Orthoptera: Acrididae) and the differential grasshopper (Melanoplus differentialis (Thomas: Orthoptera: Acrididae). Population of L. phyllopus was at its peak during the latter part of the growing season from 81 to 109 DAP. Populations of S. americana and M. differentialis declined as crop matured (61 DAP > 66 DAP >75 DAP). Results also showed that leaf and head damage did not differ among genotypes and nitrogen rates tested.