Harvesting Systems,Soil Cultivation,and Nitrogen Rate Associated with Sugarcane Yield

The adoption of mechanical harvesting of green cane gives rise to concerns as to whether systems developed under burnt cane harvesting are applicable to a green cane harvesting system. In particular, tillage, which is an integral part of the burnt cane system, may no longer be necessary, and the nitrogen fertilizer rates required may need to be replaced due to the large amounts of organic matter being returned to the soil after green cane harvesting. Mechanical harvesting is relatively new in Brazil and little is known about its effect on other sugarcane production strategies. This work aimed to evaluate sugarcane performance under not only different harvesting and cultivation systems, but also different nitrogen fertilizer rates over a 3-year period. The experimental design was a split plot with harvesting systems (burnt vs. green) as main plots, cultivation (interrow vs. no cultivation) as sub plots, and nitrogen rates as sub-sub plots. The harvesting systems produced similar sugarcane yields throughout the experimental period, which demonstrates that the harvest systems do not influence sugarcane yield. Mechanical tillage practices in interrow after harvesting had no impact on stalk yield or sugar quality, indicating no necessity for this operation in the following crop. Ratoon nitrogen fertilization promoted an increase of stalk and sugar yield, with highest yields obtained at the rate of 130 kg ha^?1 N. However, there was no interaction between harvesting system and nitrogen rate.     

Ethanol production potential of sweet sorghum assessed using forage fiber analysis procedures

Sweet sorghum (Sorghum bicolor (L.) Moench) is widely recognized as a highly promising biomass energy crop with particular potential to complement sugarcane production in diversified cropping systems. Agronomic assessments have led to identification of four cultivars well suited for such sugarcane‐based production systems in southern Louisiana. Sweet sorghum biofuel production systems are currently being developed, and research producing large sample numbers requiring ethanol yield assessment is anticipated. Fiber analysis approaches developed for forage evaluation appear to be useful for screening such large numbers of samples for relative ethanol yield. Chemical composition, forage fiber characteristics, digestibility, and ethanol production of sweet sorghum bagasse from the four cultivars were assessed. Measures of detergent fiber, lignin, and digestibility were highly correlated with ethanol production (P < 0.01). The best linear regression models accounted for about 80% of the variation among cultivars in ethanol production. Bagasse from the cultivar Dale produced more ethanol per gram of material than any of the other cultivars. This superior ethanol production was apparently associated with less lignin in stems of Dale. Forage evaluation measures including detergent fiber analyses, in vitro digestibility, and an in vitro gas production technique successfully identified the cultivar superior in ethanol yield indicating their usefulness for screening sweet sorghum samples for potential ethanol production in research programs generating large sample numbers from evaluations of germ plasm or agronomic treatments. These screening procedures reduce time and expense of alternatives such as hexose sugar assessment for calculating theoretical ethanol yield.     

The Complement of Soluble Sugars in the Saccharum Complex

The use of sugarcane as a biofactory and source of renewable biomass is being investigated increasingly due to its vigorous growth and ability to fix a large amount of carbon dioxide compared to other crops. The high biomass resulting from sugarcane production (up to 80 t/ha) makes it a candidate for genetic manipulation to increase the production of other sugars found in this research that are of commercial interest. Sucrose is the major sugar measured in sugarcane with hexoses glucose and fructose present in lower concentrations; sucrose can make up to 60% of the total dry weight of the culm. Species related to modern sugarcane cultivars were examined for the presence of sugars other than glucose, fructose and sucrose with the potential of this crop as a biofactory in mind. The species examined form part of the Saccharum complex, a closely-related interbreeding group. Extracts of the immature and mature internodes of six different species and a hybrid were analysed with gas chromatography mass spectrometry to identify mono-, di- and tri-saccharides, as well as sugar acids and sugar alcohols. Thirty two sugars were detected, 16 of which have previously not been identified in sugarcane. Apart from glucose, fructose and sucrose the abundance of sugars in all plants was low but the research demonstrated the presence of sugar pathways that could be manipulated. Since species from the Saccharum complex can be interbred, any genes leading to the production of sugars of interest could be introgressed into commercial Saccharum species or manipulated through genetic engineering.     

Response of eight sugarcane cultivars to glyphosine and glyphosate ripeners

Studies were conducted on eight sugarcane (Saccharum spp. hydrid) cultivars during the 1982–83 (plant crop) and 1983–84 (ratoon crop) growing seasons to determine the effects of glyphosine (Polaris) (N,N-bis (phosphonomethyl) glycine) and glyphosate (Polado) (sodium-N-(phosphonomethyl) glycine) on stalk sucrose content and yield. Difference due to crops (plant vs. ratoon) for sugarcane quality, kilograms of sugar per ton of cane (S/T), sugarcane yield, tons of cane per hectare (TCH), and sugar yield, tons of sugar per hectare (TSH) were significant. Significant differences were found in quality for the ratoon crop and cane and sugar yield in both crops due to ripener treatment. Cultivars in both crops differed significantly in quality and yield. Harvest dates were significantly different for all plant characteristics. Interactions of cultivar by treatment for the plant crop, harvest date by treatment for the ratoon crop, and cultivar by harvest date for both crops for cane quality also were significant. Time from ripener application to achievement of maximum sugar concentration also depended on cultivar. This is important in determining the economic benefits of a ripener treatment. Climatic conditions may also affect the benefits of such applications.     

A mixed model QTL analysis for sugarcane multiple-harvest-location trial data

Sugarcane-breeding programs take at least 12 years to develop new commercial cultivars. Molecular markers offer a possibility to study the genetic architecture of quantitative traits in sugarcane, and they may be used in marker-assisted selection to speed up artificial selection. Although the performance of sugarcane progenies in breeding programs are commonly evaluated across a range of locations and harvest years, many of the QTL detection methods ignore two- and three-way interactions between QTL, harvest, and location. In this work, a strategy for QTL detection in multi-harvest-location trial data, based on interval mapping and mixed models, is proposed and applied to map QTL effects on a segregating progeny from a biparental cross of pre-commercial Brazilian cultivars, evaluated at two locations and three consecutive harvest years for cane yield (tonnes per hectare), sugar yield (tonnes per hectare), fiber percent, and sucrose content. In the mixed model, we have included appropriate (co)variance structures for modeling heterogeneity and correlation of genetic effects and non-genetic residual effects. Forty-six QTLs were found: 13 QTLs for cane yield, 14 for sugar yield, 11 for fiber percent, and 8 for sucrose content. In addition, QTL by harvest, QTL by location, and QTL by harvest by location interaction effects were significant for all evaluated traits (30 QTLs showed some interaction, and 16 none). Our results contribute to a better understanding of the genetic architecture of complex traits related to biomass production and sucrose content in sugarcane.     

Response of eight sugarcane cultivars to glyphosine and glyphosate ripeners

Studies were conducted on eight sugarcane (Saccharum spp. hydrid) cultivars during the 1982–83 (plant crop) and 1983–84 (ratoon crop) growing seasons to determine the effects of glyphosine (Polaris) (N,N-bis (phosphonomethyl) glycine) and glyphosate (Polado) (sodium-N-(phosphonomethyl) glycine) on stalk sucrose content and yield. Difference due to crops (plant vs. ratoon) for sugarcane quality, kilograms of sugar per ton of cane (S/T), sugarcane yield, tons of cane per hectare (TCH), and sugar yield, tons of sugar per hectare (TSH) were significant. Significant differences were found in quality for the ratoon crop and cane and sugar yield in both crops due to ripener treatment. Cultivars in both crops differed significantly in quality and yield. Harvest dates were significantly different for all plant characteristics. Interactions of cultivar by treatment for the plant crop, harvest date by treatment for the ratoon crop, and cultivar by harvest date for both crops for cane quality also were significant. Time from ripener application to achievement of maximum sugar concentration also depended on cultivar. This is important in determining the economic benefits of a ripener treatment. Climatic conditions may also affect the benefits of such applications.Mention of trade name or proprietary product does not imply or constitute an endorsement or recommendation by the USDA or the University of Florida.     

九个甘蔗新品种在桂林地区的适应性观察和评价

为探讨甘蔗新品种在桂林地区的适应性表现,该研究以ROC22为对照,采用大区互比法,对国家甘蔗产业技术体系的9个甘蔗品种进行1年新植2年宿根的区域试验,观察记录出苗率、分蘖率、株高、产量和糖分等14个性状表现,并利用DTOPSIS法进行综合评价。结果表明:桂糖29号、桂糖31号、云蔗03-194、粤糖60号、福农38号和粤糖55号的综合性状表现优于对照ROC22,其中桂糖29号宿根性好、蔗茎产量和产糖量较高,但病虫害有不同程度的发生,田间栽培需加强病虫害防控;桂糖31号有效茎多、蔗糖分高,建议加强肥水管理,提高产量;云蔗03-194出苗率较高,出苗整齐,有效茎数较多,宿根性好,但枯心苗和黑穗病发病程度较其他品种严重,建议加强苗期病虫管理,保障成茎率;粤糖60号蔗糖产量较高、抗倒伏能力强,但新植出苗率较低,建议加大下种量;福农38号蔗糖分较高、抗病性较好,是优异的抗病材料;粤糖55号宿根性较好。上述筛选出的6个甘蔗品种宿根性好、抗逆性强、高产高糖,适宜在桂林地区进行扩大种植,用于指导当地的甘蔗示范推广。     

Investigating the Efficacy of Integrating Energy Crops into Non-Profitable Subfields in Iowa

Within-field spatial variability reduces growers’ return on investment and overall productivity while potentially increasing negative environmental impacts through increased soil erosion, nutrient runoff, and leaching. The hypothesis that integrating energy crops into non-profitable segments of agricultural fields could potentially increase grain yield and biomass feedstock production was tested in this study using a statewide analysis of predominantly corn- and soy-producing counties in Iowa. Basic and rigorous controls on permissible soil and soil-carbon losses were imposed on harvest of crop residues to enhance year-to-year sustainability of crop and residue production. Additional criteria limiting harvesting costs and focus on large-area subfields for biomass production were imposed to reduce the impacts of energy crop integration on grain production. Model simulations were conducted using 4 years (2013–2016) of soil, weather, crop yield, and management practice data on all counties in Iowa. Miscanthus (Miscanthus x giganteus), switchgrass (Panicum virgatum), and crop-residue-based bioenergy feedstock systems were evaluated as biomass. Average energy crop and plant residue harvesting efficiencies were estimated at 50 and 60%, respectively. Because of higher potential yields, average logistics costs for miscanthus-based biomass production were 15 and 23% lower than switchgrass-based and crop residue-based biomass productions, respectively, under basic sustainability controls, and 17 and 26% lower under rigorous sustainability controls. Subfield shape, size, area, and harvest equipment size were the dominant factors influencing harvesting cost and efficiency suggesting that in areas where subfields are predominantly profitable or harvesting efficiencies low, other options such as prairie strips, buffer zones around fields, and riparian areas should be investigated for more profitable biomass production and sustainable farming systems.     

Towards oilcane: Engineering hyperaccumulation of triacylglycerol into sugarcane stems

Metabolic engineering to divert carbon flux from sucrose to oil in high biomass crop like sugarcane is an emerging strategy to boost lipid yields per hectare for biodiesel production. Sugarcane stems comprise more than 70% of the crops' biomass and can accumulate sucrose in excess of 20% of their extracted juice. The energy content of oils in the form of triacylglycerol (TAG) is more than twofold that of carbohydrates. Here, we report a step change in TAG accumulation in sugarcane stem tissues achieving an average of 4.3% of their dry weight (DW) in replicated greenhouse experiments by multigene engineering. The metabolic engineering included constitutive co‐expression of wrinkled1; diacylglycerol acyltransferase1‐2; cysteine‐oleosin; and ribonucleic acid interference‐suppression of sugar‐dependent1. The TAG content in leaf tissue was also elevated by more than 400‐fold compared to non‐engineered sugarcane to an average of 8.0% of the DW and the amount of total fatty acids reached about 13% of the DW. With increasing TAG accumulation an increase of 18:1 unsaturated fatty acids was observed at the expense of 16:0 and 18:0 saturated fatty acids. Total biomass accumulation, soluble lignin, Brix and juice content were significantly reduced in the TAG hyperaccumulating sugarcane lines. Overcoming this yield drag by engineering lipid accumulation into late stem development will be critical to exceed lipid yields of current oilseed crops.     

Doubled sugar content in sugarcane plants modified to produce a sucrose isomer

Sucrose is the feedstock for more than half of the world's fuel ethanol production and a major human food. It is harvested primarily from sugarcane and beet. Despite attempts through conventional and molecular breeding, the stored sugar concentration in elite sugarcane cultivars has not been increased for several decades. Recently, genes have been cloned for bacterial isomerase enzymes that convert sucrose into sugars which are not metabolized by plants, but which are digested by humans, with health benefits over sucrose. We hypothesized that an appropriate sucrose isomerase (SI) expression pattern might simultaneously provide a valuable source of beneficial sugars and overcome the sugar yield ceiling in plants. The introduction of an SI gene tailored for vacuolar compartmentation resulted in sugarcane lines with remarkable increases in total stored sugar levels. The high-value sugar isomaltulose was accumulated in storage tissues without any decrease in stored sucrose concentration, resulting in up to doubled total sugar concentrations in harvested juice. The lines with enhanced sugar accumulation also showed increased photosynthesis, sucrose transport and sink strength. This remarkable step above the former ceiling in stored sugar concentration provides a new perspective into plant source–sink relationships, and has substantial potential for enhanced food and biofuel production.     

Food and bioenergy: reviewing the potential of dual‐purpose wheat crops

Within the bioenergy debate, the ‘food vs. fuel’ controversy quickly replaced enthusiasm for biofuels derived from first‐generation feedstocks. Second‐generation biofuels offer an opportunity to produce fuels from dedicated energy crops, waste materials or coproducts such as cereal straw. Wheat represents one of the most widely grown arable crops around the world, with wheat straw, a potential source of biofuel feedstock. Wheat straw currently has limited economic value; hence, wheat cultivars have been bred for increased grain yield; however, with the development of second‐generation biofuel production, utilization of straw biomass provides the potential for ‘food and fuel’. Reviewing the evidence for the development of dual‐purpose wheat cultivars optimized for food grain and straw biomass production, we present a holistic assessment of a potential ideotype for a dual‐purpose cultivar (DPC). An ideal DPC would be characterized by high grain and straw yields, high straw digestibility (i.e. biofuel yield potential) and good lodging resistance. Considerable variation in these traits exists among current wheat cultivars, facilitating the selection of improved individual traits; however, increasing straw yield and digestibility could potentially have negative trade‐off impacts on grain yield and lodging resistance, reducing the feasibility of a single ideotype. Adoption of alternative management practices could potentially increase straw yield and digestibility, albeit these practices are also associated with potential trade‐offs among cultivar traits. Benefits from using DPCs include reduced logistics costs along the biofuel feedstock supply chain, but practical barriers to differential pricing for straw digestibility traits are likely to reduce the financial incentive to farmers for growing higher ‘biofuel‐quality’ straw cultivars. Further research is required to explore the relationships among the ideotype traits to quantify potential DPC benefits; this will help to determine whether stakeholders along the bioenergy feedstock supply chain will invest in the development of DPCs that provide food and fuel potential.     

Bioenergy crop models: descriptions,data requirements,and future challenges

Field studies that address the production of lignocellulosic biomass as a source of renewable energy provide critical data for the development of bioenergy crop models. A literature survey revealed that 14 models have been used for simulating bioenergy crops including herbaceous and woody bioenergy crops, and for crassulacean acid metabolism (CAM) crops. These models simulate field‐scale production of biomass for switchgrass (ALMANAC, EPIC, and Agro‐BGC), miscanthus (MISCANFOR, MISCANMOD, and WIMOVAC), sugarcane (APSIM, AUSCANE, and CANEGRO), and poplar and willow (SECRETS and 3PG). Two models are adaptations of dynamic global vegetation models and simulate biomass yields of miscanthus and sugarcane at regional scales (Agro‐IBIS and LPJmL). Although it lacks the complexity of other bioenergy crop models, the environmental productivity index (EPI) is the only model used to estimate biomass production of CAM (Agave and Opuntia) plants. Except for the EPI model, all models include representations of leaf area dynamics, phenology, radiation interception and utilization, biomass production, and partitioning of biomass to roots and shoots. A few models simulate soil water, nutrient, and carbon cycle dynamics, making them especially useful for assessing the environmental consequences (e.g., erosion and nutrient losses) associated with the large‐scale deployment of bioenergy crops. The rapid increase in use of models for energy crop simulation is encouraging; however, detailed information on the influence of climate, soils, and crop management practices on biomass production is scarce. Thus considerable work remains regarding the parameterization and validation of process‐based models for bioenergy crops; generation and distribution of high‐quality field data for model development and validation; and implementation of an integrated framework for efficient, high‐resolution simulations of biomass production for use in planning sustainable bioenergy systems.     

甘蔗基因克隆研究进展

甘蔗是重要的糖料和能源作物,在我国,其糖产量占全国食糖产量的94%。甘蔗是高光合效率C4作物,其蔗糖含量是所有植物中最高的,其基因组中蕴藏着大量重要基因。因此,甘蔗基因克隆对甘蔗品种定向改良具有重要意义。从蔗糖代谢、生长发育和抗逆性三个方面全面总结甘蔗基因克隆的研究进展,并提出今后研究的建议,以期为今后甘蔗基因研究提供参考。     

Agronomic Considerations for Sweet Sorghum Biofuel Production in the South-Central USA

Sweet sorghum (Sorghum bicolor (L.) Moench) is currently recognized throughout the world as a highly promising biomass energy crop. Production systems and management practices for sweet sorghum have not been fully developed for the USA, although sporadic research efforts during recent decades have provided some insights into production of sweet sorghum primarily for fermentable sugar production. Field plot experiments were conducted at sites across Louisiana to assess biomass and sugar yield responses to N fertilizer, plant density, and selected cultivars. Although linear increases in stem biomass production and fermentable sugar yield were obtained with increasing N fertilizer rate under irrigated conditions, most of the increase was from the initial 45 kg N ha⁻¹ increment. Nitrogen fertilization increased stem biomass production but not fermentable sugar yield in some non-irrigated environments. Increased plant density contributed to fermentable sugar yield only under growth-limiting conditions, particularly under limited soil moisture. Location effects indicate that sweet sorghum may not be suitable for some sub-optimal cropland and pasture environments in Louisiana. During the primary growing season, cultivar did not affect fermentable sugar yields, although Dale was consistently high in sugar concentration during this period. Nitrogen fertilizer increased fermentable sugar yields only when moisture was not limiting. Overall results indicate that in environments where soil moisture limits plant growth, sugar yield responses are likely from increased plant density and not from increased N fertilization.     

Contribution of above‐ and belowground bioenergy crop residues to soil carbon

GHG mitigation by bioenergy crops depends on crop type, management practices, and the input of residue carbon (C) to the soil. Perennial grasses may increase soil C compared to annual crops because of more extensive root systems, but it is less clear how much soil C is derived from above‐ vs. belowground inputs. The objective of this study was to synthesize the existing knowledge regarding soil C inputs from above‐ and belowground crop residues in regions cultivated with sugarcane, corn, and miscanthus, and to predict the impact of residue removal and tillage on soil C stocks. The literature review showed that aboveground inputs to soil C (to 1‐m depth) ranged from 70% to 81% for sugarcane and corn vs. 40% for miscanthus. Modeled aboveground C inputs (to 30 cm depth) ranged from 54% to 82% for sugarcane, but were 67% for miscanthus. Because 50% of observed miscanthus belowground biomass is below 30 cm depth, it may be necessary to increase the depth of modeled soil C dynamics to reconcile modeled belowground C inputs with measured. Modeled removal of aboveground corn residue (25–100%) resulted in C stock reduction in areas of corn–corn–soybean rotation under conventional tillage, while no‐till management lessoned this impact. In sugarcane, soil C stocks were reduced when total aboveground residue was removed at one site, while partial removal of sugarcane residue did not reduce soil C stocks in either area. This study suggests that aboveground crop residues were the main C‐residue source to the soil in the current bioethanol sector (corn and sugarcane) and the indiscriminate removal of crop residues to produce cellulosic biofuels can reduce soil C stocks and reduce the environmental benefits of bioenergy. Moreover, a switch to feedstocks such as miscanthus with more allocation to belowground C could increase soil C stocks at a much faster rate.     

Resistance of Sugarcane Cultivars to Mahanarva fimbriolata (Stål) (Hemiptera: Cercopidae)

The spittlebug Mahanarva fimbriolata (Stål) (Hemiptera: Cercopidae) is one of the most important pests of the sugarcane crop in Brazil. Despite of its importance, there is currently a lack of information regarding sugarcane cultivars’ resistance to the spittlebug. Therefore, our objective was to evaluate the response of sugarcane genotypes to this species. Two experiments were carried out under laboratory conditions using a random block design with treatments in a factorial arrangement of 2?×?13 (experiment 1) and 2?×?12 (experiment 2), with six replicates. The first factor included two levels of infestation (infested and noninfested plants with spittlebugs), while the second consisted of the cultivars. Nymph survival varied from 47.9 to 84.5%, indicating that there are different levels of antibiosis to M. fimbriolata among the tested cultivars. The highest degree of antibiosis was found in cultivars IACSP96-7586 and IACSP96-2008, in which nymph survival was close to 48%. IACSP96-7586 also presented some degree of tolerance, but IACSP96-7569 and IACSP97-6682 stood out as the most tolerant cultivars to the pest, showing the lowest reduction in weight of aboveground biomass. On average, spittlebug infestations caused a significant reduction in relative leaf chlorophyll content and aboveground biomass weight.     

Germplasm evaluation of Kenaf (Hibiscus cannabinus) for alternative biomass for cellulosic ethanol production

Kenaf (Hibiscus cannabinus) is an annual fiber crop grown mainly in India and China. This crop is becoming a new bio‐based energy source because of its fast growth rate, excellent CO₂ absorption ability, and large productivity per unit area. In this study, we evaluated 10 different cultivars of kenaf for their potential as biomass for cellulosic ethanol production. First, kenaf samples were hydrolyzed using dilute sulfuric acid, which is the most simple and cost‐effective pretreatment method. Next, simultaneous saccharification and fermentation (SSF) of the hydrolysates were performed by wild‐type and engineered xylose‐fermenting yeast strains. The results of compositional analysis of the biomass, the hydrolysates, and the fermented products suggested that ethanol yield and productivity were significantly affected by a type of kenaf cultivars, which was not predictable based on the biomass compositions. Also, the ethanol production was maximized when the xylose fraction was utilized by engineered yeast under the control of pH to avoid acetate inhibition. Considering the sugar compositions and their fermentability, kenaf can be a promising energy‐dedicated crop for cellulosic ethanol production.     

Sugarcane (Saccharum X officinarum): A Reference Study for the Regulation of Genetically Modified Cultivars in Brazil

Global interest in sugarcane has increased significantly in recent years due to its economic impact on sustainable energy production. Sugarcane breeding and better agronomic practices have contributed to a huge increase in sugarcane yield in the last 30?years. Additional increases in sugarcane yield are expected to result from the use of biotechnology tools in the near future. Genetically modified (GM) sugarcane that incorporates genes to increase resistance to biotic and abiotic stresses could play a major role in achieving this goal. However, to bring GM sugarcane to the market, it is necessary to follow a regulatory process that will evaluate the environmental and health impacts of this crop. The regulatory review process is usually accomplished through a comparison of the biology and composition of the GM cultivar and a non-GM counterpart. This review intends to provide information on non-GM sugarcane biology, genetics, breeding, agronomic management, processing, products and byproducts, as well as the current technologies used to develop GM sugarcane, with the aim of assisting regulators in the decision-making process regarding the commercial release of GM sugarcane cultivars.