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Highlights • N rate exhibited non-significant effects on biofuel feedstock quality indices but significantly improved TEY. • CP content and protein yield as forage quality increased with application of 60 kg N ha−1. • Late summer harvest provides best quality forage while early fall harvest supplied more TEY. • Soil NO 3 − content at early fall harvest increased with increasing N rate. • A lower N rate was suitable to produce quality forage or feedstock and to avoid NO 3 − leaching on sandy soil. Abstract Switchgrass (Panicum virgatum L.) is a perennial warm-season grass which has great potential as a forage or bioenergy crop in marginal land. This study was conducted to determine whether nitrogen (N) fertilization could affect biomass quality of switchgrass harvested in late summer and early fall. The effects of four N fertilizer application rates (0, 60, 120, and 240 kg N ha−1) and two harvest times (late summer and early fall) on the quality components of forage and biofuel feedstock and theoretical ethanol yield (TEY) were investigated on a sandy wasteland (Aridisol) in Inner Mongolia, China during the growing seasons of 2015 and 2016. Soil NO 3 − content was also examined in response to N application rates. Application of 60 kg N ha−1 significantly increased switchgrass crude protein (CP) content, protein yield, and TEY (p < 0.05), but did not affect other quality parameters of forage and biofuel feedstock. Compared with the late summer harvest, CP content and protein yield were significantly lower, while TEY was significantly higher in the early fall harvest (p < 0.05); however, cellulose, hemicellulose, and ash contents showed no significant differences between the two harvest times. Acid detergent fiber (ADF) and neutral detergent fiber (NDF) contents were significantly lower for harvest in early fall than in late summer (p < 0.05). Soil NO 3 − content in early fall harvest increased significantly with increasing N application rate (p < 0.05), and was lower than that in the switchgrass green-up stage. These findings together with our results on biomass yield and apparent soil N balance suggest that a lower rate of N application appears sufficient to produce good quality forage as well as biomass without negatively affecting feedstock quality, while avoiding the risk of NO 3 − loss via leaching on a sandy soil. Switchgrass forage quality would be high during summer in terms of CP content, although delaying harvest until fall or even after a killing frost could provide better quality feedstock for bioenergy production. [ABSTRACT FROM AUTHOR]

Switchgrass (Panicum virgatum L.) is an important feedstock for bioenergy production, but establishment is difficult in cold arid areas. This study determined the conditions required to improve its germination and emergence in the field. Under controlled conditions, the effects of temperature, water status, and light on germination were studied by exposure to 12-h alternating temperatures of 15/5, 20/5, 20/10, 25/10, 35/20, 40/20, and 45/20°C (day/night) and water potentials of 0, -0.2, -0.4, -0.6, -0.8, and -1.2 MPa in culture medium. Maximum percentage germination occurred at 35/20°C, 0 MPa water potential, and in continuous dark. In the field when planted in early spring (April), no emergence occurred when there was no surface cover or covered with straw mulch (SM) whereas using plastic film mulch (FM), emergence reached 383 seedlings m-2 with pre-sowing irrigation but only 273 without irrigation. This was associated with higher soil temperatures and better soil moisture. However, in July seeding, SM lead to better water status and cooler soil conditions and thus better stand establishment. In contrast, FM treatment had poor establishment primarily due to the high temperatures. Our study indicates that emergence of switchgrass in an arid environment was (i) enhanced by pre-sowing irrigation and shallow seeding, (ii) made possible in spring by the use of FM, and (in) improved with SM for summer seeding. [ABSTRACT FROM AUTHOR]

Bioethanol will play a significant role in energy structure adjustment and greenhouse gas mitigation in the future, especially in the transport sector. As bioethanol production with grain crops may become obsolete due to food security concerns, the Chinese government has advocated the development of non-grain bioethanol. According to the current actual situation of bioethanol development and China's Liquid Biofuel Development Roadmap, we defined three stages of bioethanol development. We focused on the assessment of bioethanol feedstock resources and bioethanol yield potential in different stages using a comprehensive evaluation system integrating statistical methods, crop growth process models, and geographic information system (GIS) techniques. The considered feedstocks included corn, sweet sorghum, cassava, switchgrass, crop straw, and forest residues. The spatial–temporal characteristics of the regional bioethanol distribution were discussed. The results indicate that the total resources of corn, sweet sorghum, cassava, switchgrass, crop straws, and forest residues were about 257.17, 2083.55, 44.36, 357.56, 1031.62, and 924 million tons at different time points, respectively. In the first stage, the year 2020, the potential bioethanol totaled 21.55 million tons. An advantage in bioethanol development was demonstrated by Northeast China. A positive development situation was also identified in East China, such as in Tianjin. In the second stage, from 2020 to 2030, the potential bioethanol production is estimated to be 145.42 million tons. The bioethanol development potential will increase in South China, in areas such as Yunnan, Guangxi, and Guizhou. In the third stage, the potential bioethanol based on switchgrass is estimated to be 92.99 million tons. The potential bioethanol based on crop straws and forest residues will be 14.76 million tons if 5% of these feedstocks are fully used for producing bioethanol. Regions with a large development potential will be further expanded. Interregional bioethanol flows and international cooperation will help meet the whole nation's requirement. [ABSTRACT FROM AUTHOR]