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Crop yield variations are strongly influenced by the spatial and temporal availabilities of water and nitrogen in the soil during the crop growth season. To estimate the quantities and distributions of water and nitrogen within a given soil, process-oriented soil models have often been used. These models require detailed information about the soil characteristics and profile architecture (e.g., soil depth, clay content, bulk density, field capacity and wilting point), but high resolution information about these soil properties, both vertically and laterally, is difficult to obtain through conventional approaches. However, on-the-go electrical resistivity tomography (ERT) measurements of the soil and data inversion tools have recently improved the lateral resolutions of the vertically distributed measurable information. Using these techniques, nearly 19,000 virtual soil profiles with defined layer depths were successfully created for a 30 ha silty cropped soil over loamy and sandy substrates in Central Germany, which were used to initialise the CArbon and Nitrogen DYnamics (CANDY) model. The soil clay content was derived from the electrical resistivity (ER) and the collected soil samples using a simple linear regression approach (the mean R2 of clay = 0.39). The additional required structural and hydrological properties were derived from pedotransfer functions. The modelling results, derived soil texture distributions and original ER data were compared with the spatial winter wheat yield distribution in a relatively dry year using regression and boundary line analysis. The yield variation was best explained by the simulated soil water content (R2 = 0.18) during the grain filling and was additionally validated by the measured soil water content with a root mean square error (RMSE) of 7.5 Vol%. [ABSTRACT FROM AUTHOR]

Good canopy structure is essential for optimal maize (Zea mays L.) production. However, creating appropriate maize canopy structure can be difficult, because the characteristics of individual plants are altered by changes in plant age, density and interactions with neighbouring plants. The objective of the current study was to find a reliable method for building good maize canopy structure by analysing changes in canopy structure, light distribution and grain yield (GY). A modern maize cultivar (ZhengDan958) was planted at 12 densities ranging from 1.5 to 18 plants/m2 at two field locations in Xinjiang, China. At the silking stage (R1), plant and ear height increased with plant density as well as leaf area index (LAI), whereas leaf area per plant decreased logarithmically. The fraction of light intercepted by the plant (F) increased with increasing plant density, but the light extinction coefficient (K) decreased linearly from 0.61 to 0.39. Taking the optimum value of F (95%) as an example, and using measured values of K for each plant density at R1 and the equation from Beer's law, the corresponding (theoretical) LAI for each plant density was calculated and optimum plant density (9.72 plants/m2) obtained by calculating the difference between theoretical LAIs and actual observations. Further analysis showed that plant density ranging from 10.64 to 11.55 plants/m2 yielded a stable GY range. Therefore, taking into account the persistence time for maximum LAI, the plant density required to obtain an ideal GY maize canopy structure should be increased by 10–18% from 9.72 plants/m2. [ABSTRACT FROM AUTHOR]

Abstract: Very limited information is currently available on growth responses of switchgrass (lowland cultivars) to transient waterlogging in lowland or poorly drained areas. This study investigated impacts of microtopography‐induced transient waterlogging on switchgrass (Alamo cultivar) growth, represented by leaf‐level gas exchange and biomass yield, in an established experimental field located in the Atlantic coastal plain of North Carolina, USA. Intensive leaf‐level gas exchange measurements were conducted on switchgrass at paired spots with distinct elevations in three sub‐blocks. Aboveground biomass was randomly collected across the study field to explore the potential impacts of the transient waterlogging on biomass yield. The sum of excess water (SEW) was calculated based on measured instantaneous water table depth to generalize the relationship between biomass yield and intensity of transient waterlogging. Results showed significant (P ≤ 0.0001) treatment effects on leaf‐level gas exchange, characterized by evident reduction in both CO2 assimilation rate and stomatal conductance when water table was at or near the soil surface at low positions. Negative impacts of transient waterlogging on leaf‐level gas exchange became more evident with the increasing of elevation differences between paired subplots. Stomatal closure was found to be the main mechanism responsible for the decline of net assimilation under transient waterlogging. Aboveground biomass yields of switchgrass showed relatively high spatial variability and were positively and linearly correlated with microtopography (represented by elevation in the analysis) (P < 0.03, R2 > 0.77). Further analysis showed that biomass yields were negatively correlated with SEW (P < 0.001, R2 > 0.6) with an exponential relationship. Results of this study strongly demonstrated transient waterlogging could negatively affect switchgrass growth by suppressing leaf‐level gas exchange rates and ultimately reducing biomass yield. Findings from this study have critical implications for evaluating the economic viability of growing switchgrass on marginal lands that are subject to transient waterlogging stresses. [ABSTRACT FROM AUTHOR]

Symbiotic N2 fixation research thus far has been primarily focused on selection of bacteria. However, little progress in impacting crop yields has resulted from this approach. Bacteria introduced in field soils rarely compete well with indigenous bacteria, including mutated lines selected for high nitrogen fixation capacity. Consequently, introduction of 'elite' bacteria in fields commonly does not result in crop yield increase. This review highlights that the primary regulation of N2 fixation is a result of response of integrated physiological activity at the plant level. Nitrogen feedback from the host plant plays an important role in regulating the N2 fixation rate. Rapid sequestration of fixed nitrogen by the plant is especially important for high N2 fixation activity. In addition, water cycling in the plant between the shoot and nodules plays a key role in sustaining high N2 fixation activity. Therefore, attention in selecting the host-plant genotype is suggested to be the next step to increasing N2 fixation activity of grain legumes. [ABSTRACT FROM AUTHOR]

Abstract: Harvesting corn stover for biofuel production may decrease soil organic carbon (SOC) and increase greenhouse gas (GHG) emissions. Adding additional organic matter into soil or reducing tillage intensity, however, could potentially offset this SOC loss. Here, using SOC and life cycle analysis (LCA) models, we evaluated the impacts of land management change (LMC), that is, stover removal, organic matter addition, and tillage on spatially explicit SOC level and biofuels’ overall life cycle GHG emissions in US corn–soybean production systems. Results indicate that under conventional tillage (CT), 30% stover removal (dry weight) may reduce baseline SOC by 0.04 t C ha−1 yr−1 over a 30‐year simulation period. Growing a cover crop during the fallow season or applying manure, on the other hand, could add to SOC and further reduce biofuels’ life cycle GHG emissions. With 30% stover removal in a CT system, cover crop and manure application can increase SOC at the national level by about 0.06 and 0.02 t C ha−1 yr−1, respectively, compared to baseline cases without such measures. With contributions from this SOC increase, the life cycle GHG emissions for stover ethanol are more than 80% lower than those of gasoline, exceeding the US Renewable Fuel Standard mandate of 60% emissions reduction in cellulosic biofuels. Reducing tillage intensity while removing stover could also limit SOC loss or lead to SOC gain, which would lower stover ethanol life cycle GHG emissions to near or under the mandated 60% reduction. Without these organic matter inputs or reduced tillage intensity, however, the emissions will not meet this mandate. More efforts are still required to further identify key practical LMCs, improve SOC modeling, and accounting for LMCs in biofuel LCAs that incorporate stover removal. [ABSTRACT FROM AUTHOR]

Associative N fixation (ANF), the process by which dinitrogen gas is converted to ammonia by bacteria in casual association with plants, has not been well-studied in temperate ecosystems. We examined the ANF potential of switchgrass (Panicum virgatum L.), a North American prairie grass whose productivity is often unresponsive to N fertilizer addition, via separate short-term 15N2 incubations of rhizosphere soils and excised roots four times during the growing season. Measurements occurred along N fertilization gradients at two sites with contrasting soil fertility (Wisconsin, USA Mollisols and Michigan, USA Alfisols). In general, we found that ANF potentials declined with long-term N addition, corresponding with increased soil N availability. Although we hypothesized that ANF potential would track plant N demand through the growing season, the highest root fixation rates occurred after plants senesced, suggesting that root diazotrophs exploit carbon (C) released during senescence, as C is translocated from aboveground tissues to roots for wintertime storage. Measured ANF potentials, coupled with mass balance calculations, suggest that ANF appears to be an important source of N to unfertilized switchgrass, and, by extension, to temperate grasslands in general. [ABSTRACT FROM AUTHOR]

Bacterial inoculation of soybean seeds to improve biological nitrogen fixation is a well-known practice to achieve higher seed and protein yield with reduced fertilization. The optimal inoculation strategy in temperate regions is unknown because soybeans are rarely cultivated under colder growing conditions. The aim of the present work was to determine the most suitable inoculation strategy for soybean cultivation in Belgium. Field trials were set up with four Bradyrhizobium inoculants (HiStick, Force 48, Biodoz and Optimize) at two locations over 2 years (2014–2015) and compared with a non-inoculated control treatment. In addition, HiStick was tested at three doses and Optimize at two time periods prior to sowing. Under Belgian conditions, all inoculants were effective in establishing rhizobial symbiosis, resulting in increased yield, protein content, protein yield and thousand-grain weight compared with the non-inoculated control. A single dose of HiStick was sufficient to establish symbiosis. Pre-inoculation with Optimize 2 weeks before sowing gave an intermediate performance for most parameters between the non-inoculated control treatment and inoculation with Optimize 24 h prior to sowing. Among the four products tested, Biodoz seemed the best product for inoculation under cool growing conditions. Based on the atpD gene, the bacterial strain of Biodoz showed complete similarity with Bradyrhizobium diazoefficiens , while strains of other products were identified as Bradyrhizobium japonicum. In vitro growing capacity of the Biodoz strain at 8 °C was higher compared with the other strains. Better cold adaptation of the Biodoz strain might be a possible explanation for the better performance of Biodoz in Belgium. [ABSTRACT FROM AUTHOR]

Abstract: The mudflats along the east coast of China can be important alternative sources for arable lands after amendment. The newly reclaimed mudflats as typical saline soils are not suitable for cultivation owing to high salinity and nutrient deficiencies. The key to amending mudflat saline soils into fertile soils is to reduce salinity in the top layer of soil. Salinity reduction is usually accomplished through rainfall and freshwater irrigation. However, lack of good soil aggregation status might attribute to salt solution rise through soil capillary. Increasing soil organic matter promoted the formation of organo‐mineral complexes and clustered soil aggregates, which is a prerequisite of hindering re‐salinization, improving fertility and facilitating the evolution of coastal mudflat soil into agricultural soil. Research on the formation of clustered soil aggregates during the evolution of mudflat soil into fertile soil should focus on the formation mechanism, influencing factors and regulatory mechanism of organo‐mineral complexes in the early stage after organic matter enters the soil. In addition, exploration of the effects of the special properties of mudflat soil, for example, high saline, high pH and low levels of clay particles, on the formation and stability of organo‐mineral complexes in soil is necessary. Research on this topic can provide scientific evidences to efficiently utilize organic resources and accelerate the evolution of mudflat soil into agricultural soil. Copyright © 2017 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Choriocarcinoma is a malignant gestational trophoblastic disease and relapse or drug resistance occurs in ~25% of gestational trophoblastic tumors. Cell apoptosis serves a role in the progression from hydatidiform mole to persistent gestational trophoblastic disease. It has been demonstrated that daidzein [7‑hydroxy‑3‑(4‑hydroxyphenyl)‑4H‑chromen‑4‑one] may induce apoptosis in a number of cancer types via the mitochondrial apoptotic pathway by altering the B‑cell lymphoma (Bcl)‑2/Bcl‑2 associated X, apoptosis regulator (Bax) ratio, and activating the caspase cascade. Daidzein also serves a role in regulation of production of human chorionic gonadotropin in trophoblast cells and inhibition of cell proliferation. However, few reports have been published regarding the effect of daidzein on apoptosis in choriocarcinoma. Therefore, in the present study, JAR and JEG‑3 human gestational choriocarcinoma cells were used to investigate the effect of daidzein on apoptosis of choriocarcinoma cells. Treatment with daidzein for 48 h reduced cell viability in a dose‑dependent manner. The percentages of early and late apoptotic cells also increased following treatment with daidzein in a dose‑dependent manner, with the number of late apoptotic cells increasing more prominently. Furthermore, treatment with daidzein led to apoptosis‑associated alterations in nuclear morphology of JAR and JEG-3 cells. Expression levels of cleaved poly(ADP‑ribose) polymerase, cleaved caspase‑3 and cleaved caspase‑9 increased following treatment with daidzein, whereas the Bcl‑2/Bax ratio decreased in a dose‑dependent manner. In conclusion, the results of the present study demonstrate that daidzein may induce apoptosis of choriocarcinoma cells in a dose‑dependent manner via the mitochondrial apoptotic pathway. [ABSTRACT FROM AUTHOR]

Aims: Azospirillum brasilense is one of plant growth promoting bacteria used to improve plant growth and grain yield of cereal crops. The level of inoculation response is defined by complex plant-microorganism interactions, many of them still unknown. Thus, we evaluated both agronomic response and microbial ecology of wheat crop under A. brasilense inoculation and nitrogen fertilization at field conditions in order to improve inoculation efficiency.Methods: Treatments were: control, nitrogen fertilization and inoculation with 40M and 42M strains. Functional and structural diversity of rhizosphere bacterial communities were evaluated by community-level physiological and terminal restriction fragment length polymorphism profiles. Besides, aerial biomass, grain yield and counts of microaerophilic diazotrophic rhizobacteria were determined.Results: Plant ontogeny modified the number of culturable microaerophilic diazotrophic rhizobacteria. Although agronomic response did not show differences, plant ontogeny and the agricultural practices modified both physiology and genetic structure of rhizosphere microbial communities. Interestingly, these differences due to the treatments were observed at jointing stage but not at grain-filling stage of wheat.Conclusions: Our results demonstrate how different management decisions can change plant- microorganism relationships. While wheat could not show differences between some agricultural treatments, under the soil surface microbial communities could show them. [ABSTRACT FROM AUTHOR]

We develop an optimization-based web application for assessing biomass-to-fuels strategies based on the Biomass Utilization Superstructure (BUS) framework. This web application allows researchers with limited knowledge of optimization to assess different technologies employed at different strategies and identify the major cost drivers. The user must only provide the necessary parameters and create an optimization run after identifying the question to be addressed and the assessment metric. The web application generates visual representations of the results once the optimal solution is obtained. Finally, we demonstrate the applicability of the web application through an example. [ABSTRACT FROM AUTHOR]

Abstract: Progress on reducing nutrient loss from annual croplands has been hampered by perceived conflicts between short‐term profitability and long‐term stewardship, but these may be overcome through strategic integration of perennial crops. Perennial biomass crops like switchgrass can mitigate nitrate‐nitrogen (NO3‐N) leaching, address bioenergy feedstock targets, and – as a lower‐cost management alternative to annual crops (i.e., corn, soybeans) – may also improve farm profitability. We analyzed publicly available environmental, agronomic, and economic data with two integrated models: a subfield agroecosystem management model, Landscape Environmental Assessment Framework (LEAF), and a process‐based biogeochemical model, DeNitrification‐DeComposition (DNDC). We constructed a factorial combination of profitability and NO3‐N leaching thresholds and simulated targeted switchgrass integration into corn/soybean cropland in the agricultural state of Iowa, USA. For each combination, we modeled (i) area converted to switchgrass, (ii) switchgrass biomass production, and (iii) NO3‐N leaching reduction. We spatially analyzed two scenarios: converting to switchgrass corn/soybean cropland losing >US$ 100 ha−1 and leaching >50 kg ha−1 (‘conservative’ scenario) or losing >US$ 0 ha−1 and leaching >20 kg ha−1 (‘nutrient reduction’ scenario). Compared to baseline, the ‘conservative’ scenario resulted in 12% of cropland converted to switchgrass, which produced 11 million Mg of biomass and reduced leached NO3‐N 18% statewide. The ‘nutrient reduction’ scenario converted 37% of cropland to switchgrass, producing 34 million Mg biomass and reducing leached NO3‐N 38% statewide. The opportunity to meet joint goals was greatest within watersheds with undulating topography and lower corn/soybean productivity. Our approach bridges the scales at which NO3‐N loss and profitability are usually considered, and is informed by both mechanistic and empirical understanding. Though approximated, our analysis supports development of farm‐level tools that can identify locations where both farm profitability and water quality improvement can be achieved through the strategic integration of perennial vegetation. [ABSTRACT FROM AUTHOR]

Based on experimental data from laboratory and field, numerous authors have raised concern that exposure to glyphosate-based herbicides (GBHs) may pre-dispose crops to damage by microbial pathogens. In this review, we distinguish and evaluate two principal pathways by which GBHs may affect the susceptibility of crops to disease: pathway 1-via disruptions to rhizosphere microbial ecology, and pathway 2-via restriction of nutrients to crops. We conclude that GBHs have the potential to undermine crop health in a number of ways, including: (i) impairment of the innate physiological defences of glyphosate-sensitive (GS) cultivars by interruption of the shikimic acid pathway; (ii) impairment of physiological disease defences has also been shown to occur in some glyphosate-resistant (GR) cultivars, despite their engineered resistance to glyphosate's primary mode of action; (iii) interference with rhizosphere microbial ecology (in particular, GBHs have the potential to enhance the population and/or virulence of some phytopathogenic microbial species in the crop rhizosphere); and finally, (iv) the as yet incompletely elucidated reduction in the uptake and utilisation of nutrient metals by crops. Future progress will best be achieved when growers, regulators and industry collaborate to develop products, practices and policies that minimise the use of herbicides as far as possible and maximise their effectiveness when used, while facilitating optimised food production and security. [ABSTRACT FROM AUTHOR]

The mandate by the Energy Independence and Security Act of 2007 to increase renewable fuel production in the USA has resulted in extensive research into the sustainability of perennial bioenergy crops such as switchgrass ( Panicum virgatum) and miscanthus ( Miscanthus× giganteus). Perennial grassland crops have been shown to support greater aboveground biodiversity and ecosystem function than annual crops. However, management considerations, such as what crop to plant or whether to use fertilizer, may alter belowground diversity and ecosystem functioning associated with these grasslands as well. In this study, we compared crop type (switchgrass or miscanthus) and nitrogen fertilization effects on arbuscular mycorrhizal fungal ( AMF) and soil nematode abundance, activity, and diversity in a long-term experiment. We quantified AMF root colonization, AMF extra-radical hyphal length, soil glomalin concentrations, AMF richness and diversity, plant-parasitic nematode abundance, and nematode family richness and diversity in each treatment. Mycorrhizal activity and diversity were higher with switchgrass than with miscanthus, leading to higher potential soil carbon contributions via increased hyphal growth and glomalin production. Plant-parasitic nematode ( PPN) abundance was 2.3 × higher in miscanthus plots compared to switchgrass, mostly due to increases in dagger nematodes ( Xiphinema). The higher PPN abundance in miscanthus may be a consequence of lower AMF in this species, as AMF can provide protection against PPN through a variety of mechanisms. Nitrogen fertilization had minor negative effects on AMF and nematode diversity associated with these crops. Overall, we found that crop type and fertilizer application associated with perennial bioenergy cropping systems can have detectable effects on the diversity and composition of soil communities, which may have important consequences for the ecosystem services provided by these systems. [ABSTRACT FROM AUTHOR]

Agricultural anaerobic digestion plants have recently become a typical part of rural landscape in the Czech Republic due to massive governmental subvention programmes. Yet, their potential as an effective tool how to response to global climate changes at a local level is rather underused (maize used as a primary input mainly, usage of waste heat is limited, etc.). This situation is caused by misguided subvention policies. The aim of this contribution is first to analyse the agricultural anaerobic digestion plants in the rural space of the Moravian-Silesian Region, and second, to deepen the knowledge on the perception of the digestion plants among the population of municipalities in which such facility was constructed. A questionnaire survey has been carried out in three model municipalities ( n = 369) located in the Moravian-Silesian Region. Several recommendations and notes for public administration and potential investors concerning the location of future anaerobic digestion plants projects and settings of supportive programmes have been defined. [ABSTRACT FROM AUTHOR]

Switchgrass ( Panicum virgatum) productivity on marginal and fertile lands has not been thoroughly evaluated in a systematic manner that includes soil-crop-weather-management interactions and to quantify the risk of failure or success in growing the crop. We used the Systems Approach to Land Use Sustainability ( SALUS) model to identify areas with low risk of failing to having more than 8000 kg ha−1 yr−1 switchgrass aboveground net primary productivity ( ANPP) under rainfed and unfertilized conditions. In addition, we diagnosed constraining factors for switchgrass growth, and tested the effect of nitrogen fertilizer application on plant productivity across Michigan for 30 years under three climate scenarios (baseline climate in 1981-2010, future climate with emissions using RCP 2.6 and RCP 6.0). We determined that <16% of land in Michigan may have at least 8 Mg ha−1 yr−1 ANPP under rainfed and unfertilized management with a low risk of failure. Of the productive low-risk land, about 25% was marginal land, with more than 80% of which was affected by limited water availability due to low soil water-holding capacity and shallow depth. About 80% of the marginal land was N limited under baseline conditions, but that percentage decreased to 58.5% and 42.1% under RCP 2.6 and RCP 6.0 climate scenarios, respectively, partly due to shorter growing season, smaller plants and less N demand. We also found that the majority of Michigan's land could have high switchgrass ANPP and low risk of failure with no more than 60 kgN ha−1 fertilizer input. We believe that the methodology used in this study works at different spatial scales, as well as for other biofuel crops. [ABSTRACT FROM AUTHOR]

BACKGROUND Organic production is widely assumed to affect quality and nutritional parameters of arable crops. A field experiment was started in 2009 following integrated ( INT), organic ( ORG) and biodynamic ( BD) production standards for wheat, maize and rapeseed production. With resort to standard analytical procedures and chemometrics, compositional parameters of Brassica napus L. 'Siska' seed (water, protein, oil and glucosinolate content) by non-destructive near-infrared spectroscopy ( NIRS), and fatty acid composition determined by gas chromatography, were assessed. RESULTS The BD and ORG production systems positively influenced oleic fatty acid and oil content in comparison to INT, which had higher levels of protein and water content (19.8% and 4.7%, respectively), as well as linolenic (3.8%), gadoleic (12.6%) and hexadecadienoic (15.5%) fatty acids. Increases in the listed parameters were linked to mineral fertilizer application in the INT production system. With principal component analysis ( PCA) the INT samples were clearly differentiated. The PCA results were influenced by differences in linolenic, gadoleic and behenic fatty acid levels as well as protein and water content. CONCLUSION Because quality parameters in rapeseed are increased in alternative production systems, production with an understanding of the soil processes and yield formation presents an opportunity for ORG and BD farmers. © 2016 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

In this work, we explore the ability of several characterization approaches for phenotyping to extract information about plant cell wall properties in diverse maize genotypes with the goal of identifying approaches that could be used to predict the plant's response to deconstruction in a biomass-to-biofuel process. Specifically, a maize diversity panel was subjected to two high-throughput biomass characterization approaches, pyrolysis molecular beam mass spectrometry (py-MBMS) and near-infrared (NIR) spectroscopy, and chemometric models to predict a number of plant cell wall properties as well as enzymatic hydrolysis yields of glucose following either no pretreatment or with mild alkaline pretreatment. These were compared to multiple linear regression (MLR) models developed from quantified properties. We were able to demonstrate that direct correlations to specific mass spectrometry ions from pyrolysis as well as characteristic regions of the second derivative of the NIR spectrum regions were comparable in their predictive capability to partial least squares (PLS) models for p-coumarate content, while the direct correlation to the spectral data was superior to the PLS for Klason lignin content and guaiacyl monomer release by thioacidolysis as assessed by cross-validation. The PLS models for prediction of hydrolysis yields using either py-MBMS or NIR spectra were superior to MLR models based on quantified properties for unpretreated biomass. However, the PLS models using the two high-throughput characterization approaches could not predict hydrolysis following alkaline pretreatment while MLR models based on quantified properties could. This is likely a consequence of quantified properties including some assessments of pretreated biomass, while the py-MBMS and NIR only utilized untreated biomass. [ABSTRACT FROM AUTHOR]

Wood is a limited resource which is exposed to a continuously growing global demand not least because of a politically fostered bioenergy use. One approach to master the challenge to sustainably meet this increasing wood demand is short rotation forestry ( SRF). However, SRF is only gradually evolving and it is not fully understood which determinants hamper its expansion. This study provides theoretical insights into economic and environmental determinants of an SRF expansion and their interplay. This assessment requires the incorporation of farmers' decision-making based on an explicit investment appraisal. Therefore, we use an agent-based model to depict the decision-making of profit-maximizing farmers facing the choice between SRF, the cultivation of conventional annual agricultural crops and abstaining from cultivation (fallow land). The land use decisions are influenced by general economic determinants, such as market prices for wood and annual crops, and by site-dependent determinants, such as the environmental site quality. We found that the willingness to pay for SRF-based products and for annual crops most strongly influences the coverage of SRF in the landscape. SRF will in most cases be established on sites with low productivity. However, a decrease in the willingness to pay for annual crops will lead to a reallocation of SRF plantations to sites with higher productivity. Furthermore, our model results indicate that the impact of the distance to processing plants on farmers' decisions strongly depends on general economic determinants and the given spatial structure of the underlying natural landscape. Analysing the relative importance of different determinants of an SRF expansion, this study gives insights into the approach of using SRF to sustainably meet the growing wood demand. Moreover, these insights are taken as a starting point for the design of effective government interventions to promote SRF. [ABSTRACT FROM AUTHOR]

If the US mandates for the use of cellulosic biofuels are ultimately enforced, cellulosic feedstock will be demanded. Native switchgrass is a cellulosic feedstock that has been of substantial interest for this purpose because it is widely grown across the USA, it can be grown on marginal cropland and thus compete minimally with food supplies, it has a low carbon footprint, and in many ways, it is a sustainable source of energy. The purpose of the research reported here is to quantify the potential willingness of producers across 358 counties in a 10-state area in North Central USA to produce this biomass. We conducted a contingent valuation survey of randomly selected farm operators in this area. From the more than 1100 responses, we found that the mean reservation price at which respondents were willing to supply switchgrass from their least productive field is a return of about $228 per acre, which translates to about $82 per dry ton. Respondents were somewhat less willing to lease out their land for this purpose, requiring an additional $3.50 per dry ton to be willing to lease. In sub-regions of counties grouped by opportunity cost, mean reservation prices are equivalent to $75 per ton, $82 per ton, and $99 per ton, very close in the first two subregions to the Department of Energy goal of $84 per dry ton delivered to the biorefinery. Thus, prospects appear favorable that substantial fractions of farmers would be willing to supply switchgrass in this area, particularly in the sub-areas with lower land costs. © 2017 Society of Chemical Industry and John Wiley & Sons, Ltd [ABSTRACT FROM AUTHOR]

Interest from the US commercial aviation industry and commitments established by the US Navy and Air Force to use renewable fuels has spurred interest in identifying and developing crops for renewable aviation fuel. Concern regarding greenhouse gas emissions associated with land-use change and shifting land grown for food to feedstock production for fuel has encouraged the concept of intensifying current prominent cropping systems through various double cropping strategies. Camelina ( Camelina sativa L.) and field pennycress ( Thlaspi arvense L.) are two winter oilseed crops that could potentially be integrated into the corn ( Zea mays L.)-soybean [( Glycine max (L.) Merr.] cropping system, which is the prominent cropping system in the US Corn Belt. In addition to providing a feedstock for renewable aviation fuel production, integrating these crops into corn-soybean cropping systems could also potentially provide a range of ecosystem services. Some of these include soil protection from wind and water erosion, soil organic C (SOC) sequestration, water quality improvement through nitrate reduction, and a food source for pollinators. However, integration of these crops into corn-soybean cropping systems also carries possible limitations, such as potential yield reductions of the subsequent soybean crop. This review identifies and discusses some of the key benefits and constraints of integrating camelina or field pennycress into corn-soybean cropping systems and identifies generalized areas for potential adoption in the US Corn Belt. [ABSTRACT FROM AUTHOR]

Knowledge of production-system performance is largely based on observations at the experimental plot scale. Although yield gaps between plot-scale and field-scale research are widely acknowledged, their extent and persistence have not been experimentally examined in a systematic manner. At a site in southwest Michigan, we conducted a 6-y experiment to test the accuracy with which plot-scale crop-yield results can inform field-scale conclusions. We compared conventional versus alternative, that is, reduced-input and biologically based-organic, management practices for a corn- soybean-wheat rotation in a randomized complete block-design experiment, using 27 commercial-size agricultural fields. Nearby plot-scale experiments (0.02-ha to 1.0-ha plots) provided a comparison of plot versus field performance. We found that plot-scale yields well matched field-scale yields for conventional management but not for alternative systems. For all three crops, at the plot scale, reduced-input and conventional managements produced similar yields; at the field scale, reduced-input yields were lower than conventional. For soybeans at the plot scale, biological and conventional managements produced similar yields; at the field scale, biological yielded less than conventional. For corn, biological management produced lower yields than conventional in both plot- and field-scale experiments. Wheat yields appeared to be less affected by the experimental scale than corn and soybean. Conventional management was more resilient to field-scale challenges than alternative practices, which were more dependent on timely management interventions; in particular, mechanical weed control. Results underscore the need for much wider adoption of field-scale experimentation when assessing new technologies and production-system performance, especially as related to closing yield gaps in organic farming and in low-resourced systems typical of much of the developing world. [ABSTRACT FROM AUTHOR]

Reducing tillage intensity and diversifying crop rotations may improve the sustainability of irrigated cropping systems in semi-arid regions. The objective of this study was to compare the greenhouse gas (GHG) emissions, soil organic matter, and net global warming potential (net GWP) of a sugar beet ( Beta vulgaris L.)-corn ( Zea mays L,) rotation under conventional (CT) and reduced-tillage (RT) and a corn-dry bean ( Phaseolus vulgaris L.) rotation under organic (OR) management during the third and fourth years of 4-year crop rotations. The gas and soil samples were collected during April 2011-March 2013, and were analyzed for carbon dioxide (CO), methane (CH), and nitrous oxide (NO) emissions, water-filled pore space (WFPS), soil nitrate (NO -N) and ammonium (NH -N) concentrations, soil organic carbon (SOC) and total nitrogen (TN), and net global warming potential (net GWP). Soils under RT had 26% lower CO emissions compared to 10.2 kg C ha day and 43% lower NO emissions compared to 17.5 g N ha day in CT during cropping season 2011, and no difference in CO and NO emissions during cropping season 2012. The OR emitted 31% less NO, but 74% more CO than CT during crop season 2011. The RT had 34% higher SOC content than CT (17.9 Mg ha) while OR was comparable with CT. Net GWP was negative for RT and OR and positive for CT. The RT and OR can increase SOC sequestration, mitigate GWP and thereby support in the development of sustainable cropping systems in semiarid agroecosystems. [ABSTRACT FROM AUTHOR]

Background: Interannual variability in precipitation, particularly drought, can affect lignocellulosic crop biomass yields and composition, and is expected to increase biofuel yield variability. However, the effect of precipitation on downstream fermentation processes has never been directly characterized. In order to investigate the impact of interannual climate variability on biofuel production, corn stover and switchgrass were collected during 3 years with significantly different precipitation profiles, representing a major drought year (2012) and 2 years with average precipitation for the entire season (2010 and 2013). All feedstocks were AFEX (ammonia fiber expansion)-pretreated, enzymatically hydrolyzed, and the hydrolysates separately fermented using xylose-utilizing strains of Saccharomyces cerevisiae and Zymomonas mobilis. A chemical genomics approach was also used to evaluate the growth of yeast mutants in the hydrolysates. Results: While most corn stover and switchgrass hydrolysates were readily fermented, growth of S. cerevisiae was completely inhibited in hydrolysate generated from drought-stressed switchgrass. Based on chemical genomics analysis, yeast strains deficient in genes related to protein trafficking within the cell were significantly more resistant to the drought-year switchgrass hydrolysate. Detailed biomass and hydrolysate characterization revealed that switchgrass accumulated greater concentrations of soluble sugars in response to the drought and these sugars were subsequently degraded to pyrazines and imidazoles during ammonia-based pretreatment. When added ex situ to normal switchgrass hydrolysate, imidazoles and pyrazines caused anaerobic growth inhibition of S. cerevisiae. Conclusions: In response to the osmotic pressures experienced during drought stress, plants accumulate soluble sugars that are susceptible to degradation during chemical pretreatments. For ammonia-based pretreatment, these sugars degrade to imidazoles and pyrazines. These compounds contribute to S. cerevisiae growth inhibition in drought-year switchgrass hydrolysate. This work discovered that variation in environmental conditions during the growth of bioenergy crops could have significant detrimental effects on fermentation organisms during biofuel production. These findings are relevant to regions where climate change is predicted to cause an increased incidence of drought and to marginal lands with poor water-holding capacity, where fluctuations in soil moisture may trigger frequent drought stress response in lignocellulosic feedstocks. [ABSTRACT FROM AUTHOR]

Landscape design has been embraced as a promising approach to holistically balance multiple goals related to environmental and resource management processes to meet future provisioning and regulating ecosystem services needs. In the agricultural context, growing bioenergy crops in specific landscape positions instead of dedicated fields has the potential to improve their sustainability, provide ecosystem services, and minimize competition with other land uses. However, growing bioenergy crops in sub-productive or environmentally vulnerable parts of a field implies more complex logistics as small amounts of biomass are generated in a distributed way across the landscape. We present a novel assessment of the differences in production and logistic costs between business as usual (BAU, dedicated fields), and distributed landscape production of shrub, or short-rotation willow for bioenergy within a US Midwestern landscape. Our findings show that regardless of the mode of cropping, BAU or landscape design, growing shrub willows is unlikely to provide positive revenues (−$67 to -$303 ha−1 yr−1 at a biomass price of $46.30 Mgwet−1) because of high land rental costs in this agricultural region. However, when translated into a practice cost per unit of N removed at the watershed scale (range: $1.8-37.0 kg N−1 yr−1), the net costs are comparable to other conservation practices. The projected opportunity cost of growing willows instead of corn on underproductive areas varied between -$14 and $49 Mgwet−1. This highlights the potential for willows to be a cost effective choice depending on the intra-field grain productivity, biomass price and desirable concurrent ecosystem services. © 2016 The Authors. Biofuels, Bioproducts and Biorefining published by Society of Chemical Industry and John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Perennial, cellulosic bioenergy crops represent a risky investment. The potential for adoption of these crops depends not only on mean net returns, but also on the associated probability distributions and on the risk preferences of farmers. Using 6-year observed crop yield data from highly productive and marginally productive sites in the southern Great Lakes region and assuming risk neutrality, we calculate expected breakeven biomass yields and prices compared to corn ( Zea mays L.) as a benchmark. Next we develop Monte Carlo budget simulations based on stochastic crop prices and yields. The crop yield simulations decompose yield risk into three components: crop establishment survival, time to maturity, and mature yield variability. Results reveal that corn with harvest of grain and 38% of stover (as cellulosic bioenergy feedstock) is both the most profitable and the least risky investment option. It dominates all perennial systems considered across a wide range of farmer risk preferences. Although not currently attractive for profit-oriented farmers who are risk neutral or risk averse, perennial bioenergy crops have a higher potential to successfully compete with corn under marginal crop production conditions. [ABSTRACT FROM AUTHOR]

As the effects of climate change continue to alter crop-growing conditions year-to-year on both prime and marginal agricultural landscapes, we must consider the effects not only on yield but also on quality. This is particularly true for oilseed crops. In this review, we explore the importance of oilseeds in general and the specific uses of major oilseed crops including soybean, sunflower, canola, peanut, and cottonseed. We review the physiology of seed oil production, from the perspective of the plant's adaptation to environmental changes. Of particular importance is the role of temperature and water availability on oil synthesis. We then discuss how this influences genetic variation, phenotype variability due to environment, and the interaction of genetics and environment to affect composition and yield of vegetable oils. The ability to predict these effects using genomics and bioinformatics is an important new frontier for breeders to maximize stability of a desired fatty acid composition for their crop over increasingly extreme agricultural environments.

High weed abundance in organic crops is thought to be a key factor contributing to the greater yield loss in organic as compared with conventional cropping systems. However, even with greater weed densities than conventional systems, some organic systems have yields comparable to conventional systems, suggesting that cropping systems might differ in yield loss due to weed competition. The diversity in soil nutrient resources due to diversity in crop rotations and variable inputs might enhance crop tolerance to weed competition. We assessed the long-term effects of contrasting levels of crop rotations (low, medium and high diversity) on weed density, weed biomass and wheat yield loss in organic and no-till conventional cropping systems using a microplot study within a long-term cropping systems trial at Scott, Saskatchewan, Canada. Weed density and biomass were found to be four times higher in the organic systems than in the conventional systems. Under standard weed management practices, organic had 44% lower yield than the conventional system. Lower yields in organic, even without weed competition, suggest that the lower yields are due to low soil productivity rather than weed competition. No differences in yield loss were observed among the organic and conventional systems or among the diverse crop rotations. We conclude that the organic management practices and/or increased crop rotation diversity did not enhance yield or reduce yield loss due to weed competition, due to the factors associated with lower soil fertility. [ABSTRACT FROM AUTHOR]

Cassava pulp (CP), a by-product from the cassava starch industry, is a potential resource for ethanol production. Ammonia gas absorption fiber expansion (AGAFE) was developed to accomplish efficient saccharification of CP. AGAFE was designed to be used under moderate pressure by directly adding compressed ammonia gas before rapidly releasing the pressure. Scanning electron microscopy analysis showed that the cell wall of AGAFE-pretreated CP was severely disrupted, while the fiber of the raw CP remained largely intact. Additionally, the concentration of glucose released from the hydrolysis of pretreated CP was higher than that obtained from raw CP using α-amylase and glucoamylase. The optimum pretreatment conditions for AGAFE were 0.2 MPa and 70 °C for 10 min, which resulted in saccharification of 83.16 % of the total starch in CP. In contrast, only 53.73 % saccharification was achieved when raw CP was directly hydrolyzed without pretreatment, suggesting that destruction of the starch and fiber in CP was necessary to obtain maximum saccharification. To confirm whether the AGAFE pretreatment influenced ethanol fermentation, a fermentation test using the hydrolysate from AGAFE-pretreated CP was carried out using Saccharomyces cerevisiae NCYC3233 and Kluyveromyces marxianus TISTR5925. When the hydrolysates containing 10.1 % ( w/ v) glucose were subjected to fermentation, 5.0 and 4.5 % ( w/ v) ethanol was produced, respectively, indicating that >85 % of the theoretical yields were achieved without inhibition from any mixture components. These results indicated that AGAFE is a useful pretreatment option for ethanol production from biomass containing starch and fiber such as CP. [ABSTRACT FROM AUTHOR]

A primary goal of many next-generation bioenergy systems is to increase ecosystem services such as soil carbon (C) storage and nutrient retention. Evaluating whether bioenergy management systems are achieving these goals is challenging in part because these processes occur over long periods of time at varying spatial scales. Investigation of microbially mediated soil processes at the microbe scale may provide early insights into the mechanisms driving these long-term ecosystem services. Furthermore, seasonal fluctuations in microbial activity are rarely considered when estimating whole ecosystem functioning, but are central to decomposition, soil structure, and realized C storage. Some studies have characterized extracellular enzyme activity within soil structures (aggregates); however, seasonal variation in decomposition at the microscale remains virtually unknown, particularly in managed ecosystems. As such, we hypothesize that temporal variation in aggregate turnover is a strong regulator of microbial activity, with important implications for decomposition and C and nitrogen (N) storage in bioenergy systems. We address variation in soil microbial extracellular enzyme activity spatially across soil aggregates and temporally across two growing seasons in three ecosystems managed for bioenergy feedstock production: Zea mays L. (corn) agroecosystem, fertilized and unfertilized reconstructed tallgrass prairie. We measured potential N-acetyl-glucosaminidase ( NAG), β-glucosidase ( BG), β-xylosidase ( BX), and cellobiohydrolase ( CB) enzyme activity. Aggregate turnover in prairie systems was driven by precipitation events and seasonal spikes in enzyme activity corresponded with aggregate turnover events. In corn monocultures, soil aggregates turned over early in the growing season, followed by increasing, albeit low, enzyme activity throughout the growing season. Independent of management system or sampling date, NAG activity was greatest in large macroaggregates (>2000 μm) and CB activity was greatest in microaggregates (<250 μm). High microbial activity coupled with greater aggregation in prairie bioenergy systems may reduce loss of soil organic matter through decomposition and increase soil C storage. [ABSTRACT FROM AUTHOR]

Improving crop productivity through higher plant density requires a detailed understanding of organ development in response to increased interplant competition. The objective of this paper is thus to investigate the characteristics of organ development under increased interplant competition. A field experiment was conducted to investigate organ development across 4 maize plant densities i.e. 2, 6, 12 and 20 plants m–2 (referred to PD2, PD6, PD12 and PD20 respectively). In response to increased interplant competition, lengths of both laminae and sheaths increased in lower phytomers, but decreased in upper phytomers. Sheath extension appeared to be less sensitive to increased interplant competition than lamina extension. Extension of laminae and internodes responded to increased plant density as soon as onset of mild interplant competition, but did not respond any further to severe competition. Both lamina width and internode diameter were reduced due to a smaller growth rate in response to increased plant density. Overall, this study identified that organ expansion rate can be taken as the key morphological factor to determine the degree of interplant competition. [ABSTRACT FROM AUTHOR]

Because soil microbes drive many of the processes underpinning ecosystem services provided by soils, understanding how cropping systems affect soil microbial communities is important for productive and sustainable management. We characterized and compared soil microbial communities under restored prairie and three potential cellulosic biomass crops (corn, switchgrass, and mixed prairie grasses) in two spatial experimental designs - side-by-side plots where plant communities were in their second year since establishment (i.e., intensive sites) and regionally distributed fields where plant communities had been in place for at least 10 years (i.e., extensive sites). We assessed microbial community structure and composition using lipid analysis, pyrosequencing of rRNA genes (targeting fungi, bacteria, archaea, and lower eukaryotes), and targeted metagenomics of nifH genes. For the more recently established intensive sites, soil type was more important than plant community in determining microbial community structure, while plant community was the more important driver of soil microbial communities for the older extensive sites where microbial communities under corn were clearly differentiated from those under switchgrass and restored prairie. Bacterial and fungal biomasses, especially biomass of arbuscular mycorrhizal fungi, were higher under perennial grasses and restored prairie, suggesting a more active carbon pool and greater microbial processing potential, which should be beneficial for plant acquisition and ecosystem retention of carbon, water, and nutrients. [ABSTRACT FROM AUTHOR]

Soil organic carbon is one of the most important soil components, which acts as a sink for atmospheric CO. In order to calculate the carbon budget of a region, the effect of soil and plant management practice on carbon sequestration in soils needs to be quantified. The objective of this study was to investigate carbon sequestration effect of the biological operating system (pit seeding) in three depths as affected by Eurotia ceratoides application. For this purpose, the experiments were carried out as split plots based on completely block randomized design. The experimental plots of E. ceratoides were cultivated by pit seeding method. Then, soil samples were collected from 0- to 10-, 10- to 20-, and 20- to 40-cm depth. Plant samples were selected that pass a 20-mesh sieve before performing the element analysis. The result indicated that application of pit-seeding method in carbon sequestration (CS) and soil organic carbon (SOC) are effective. In addition, CS and SOC in soil surface (0 to 10 cm) is 8 to 10 % higher than depth of soil especially when pit seeding method was applied. Stock carbon is also the highest in litter of plant (3 to 5 %). The finding of this research reveals the necessity of paying more attention to the role of biological operating system through conservation method in carbon sequestration and prevention of increasing global warming. [ABSTRACT FROM AUTHOR]

This study applies life cycle assessment (LCA) techniques to evaluate the processes controling the environmental impacts of anaerobic digestion (AD) pathways on a modeled dairy farm setting representative of Wisconsin. Seven electricity-producing AD pathways are compared against a base-case (BC) pathway to understand the effect of management practices, co-digestion strategies, and energy conversion processes on greenhouse gas (GHG) emissions, ammonia (NH3) emissions, depletion of fossil fuels (DFF), and nutrient balances. The pathway selected has a substantial influence on the estimates of environmental impacts. GHG emissions range from 178 to 267 kg CO2-eq GJ−1, NH3 emissions range from 11 to 18 kg GJ−1, DFF range from 176 to 327 MJ GJ−1, and N availability ranges from 7 to 15 kg GJ−1 of produced energy. The results of this paper show that the environmental benefits and concerns of anaerobic digestion systems can be further improved with the adoption of management practices on-farm. Injection of digestate during land application is an effective management practice to reduce NH3 emissions, which at the same time increases N availability and reduces GHG emissions and DFF given that the manufacturing of purchased fertilizers is fossil energy intensive. Co-digesting manure with corn stover and switchgrass increases energy production. Recovering heat has proven to be an easy to adopt strategy that improves all sustainability indicators without implementing major operational changes. Finally, 100 kg CO2-eq GJ−1, 4.2 kg NH3 GJ−1 and 566 MJ GJ−1 are determined for GHG emissions, NH3 emissions and DFF respectively for a compressed biogas pathway. © 2015 Society of Chemical Industry and John Wiley & Sons, Ltd [ABSTRACT FROM AUTHOR]

Second-generation bioethanol can be produced from various lignocellulosic biomasses such as wood, agricultural or forest residues. Lignocellulosic biomass is inexpensive, renewable and abundant source for bioethanol production. The conversion of lignocellulosic biomass to bioethanol could be a promising technology though the process has several challenges and limitations such as biomass transport and handling, and efficient pretreatment methods for total delignification of lignocellulosics. Proper pretreatment methods can increase concentrations of fermentable sugars after enzymatic saccharification, thereby improving the efficiency of the whole process. Conversion of glucose as well as xylose to bioethanol needs some new fermentation technologies to make the whole process inexpensive. The main goal of pretreatment is to increase the digestibility of maximum available sugars. Each pretreatment process has a specific effect on the cellulose, hemicellulose and lignin fraction; thus, different pretreatment methods and conditions should be chosen according to the process configuration selected for the subsequent hydrolysis and fermentation steps. The cost of ethanol production from lignocellulosic biomass in current technologies is relatively high. Additionally, low yield still remains as one of the main challenges. This paper reviews the various technologies for maximum conversion of cellulose and hemicelluloses fraction to ethanol, and it point outs several key properties that should be targeted for low cost and maximum yield. [ABSTRACT FROM AUTHOR]

Pennsylvania farmers have a long history of harvesting corn ( Zea mays L.) stover after grain harvest for animal bedding and feed or as a component of mushroom compost, or as silage for dairy cattle feed. With the shallow soils and rolling topography, soil erosion and carbon losses have been minimized through extensive use of cover crops, no-till, and organic matter additions from animal manure. Our objective was to determine the effect of harvesting corn stover as a feedstock for bioenergy production in continuous corn or corn-soybean [ Glycine max (L.) Merr.] rotations on corn grain and stover yields, soil carbon, nitrogen, phosphorus, potassium, and the potential for cover crops to mitigate negative impacts of stover harvest. Although there was not a significant effect of stover harvest on corn grain yields in continuous corn, stover harvest tended to increase yields in years with wet springs but decreased them in dry years. Under the corn soybean rotation, 100 % stover removal always resulted in lower grain yields. The harvest index (HI) varied from 0.45 to >0.6 over the 5-year period with the lowest HI values being in response to a late summer drought and highest values being associated with an early summer drought. In most cases, 60 % soil cover was maintained in fall and spring with 50 % harvest of corn stover. Without a rye ( Secale cereale L.) cover crop, surface residue for 100 % stover harvest ranged from 20 to 30 %, whereas it was greater than 40 % when rye was established promptly in the fall. Soil carbon was similar across stover removal levels, crop rotations, and cover crops, as were soil nitrogen, phosphorus, and potassium concentrations, since nutrient removal by the grain and stover were replaced with fertilizer additions. Based on the crop yield, surface cover, and soil nutrient responses, partial stover removal could be sustainable under typical climate and management practices in Pennsylvania. [ABSTRACT FROM AUTHOR]

Models can provide researchers with an opportunity to understand the multidimensional relationships among factors affecting crop growth. All such factors, including field condition, must be tested using models. The main objective of this study was to apply the Cropping System Model (CSM)-Crop-Environment Resource Synthesis (CERES)-Wheat model to uneven areas for simulating rainfed wheat. First, the model was calibrated at a field cultivated with wheat variety Sardari. The model was then applied to different points at a ‘hummocky’ evaluation site. At this site, 69 sample points from 5 different slope positions (summit, shoulder, backslope, footslope, and toeslope) were specified and physical and chemical soil properties as well as final grain and total aboveground wheat biomass at each of 69 points were measured. The overall results showed that the normalized root-mean-square error varied between 15% and 34% for the top weight; this was considered to be good enough for undulating areas. The model efficiency (EF) also ranged from 0.35 to 0.26 both in simulation of final grain and in top weight. It can be concluded that CSM-CERES-Wheat model can be effectively applied for yield prediction in hills. It should be noted that use of the CSM-CERES-Wheat model is not recommended for estimation of grain yield in individual slope positions unless more detailed water and fertilizer data are also available. [ABSTRACT FROM AUTHOR]

No-till practices are restoring and protecting soil health and are considered critical for achieving sustainability of global agriculture. Organic producers in the USA would like to no-till, but are concerned about managing weeds without tillage. In conventional agriculture, no-till improves weed management in diverse rotations when crops are arranged in 2-year intervals of cool season and warm season crops. A similar approach with organic rotations may enable producers to also accrue the weed management benefit of no-till in organic farming along with restoring soil health. Here, we review the benefits gained for weed management when a complex rotation is integrated with continuous no-till. The complex rotation included 3 years of a perennial legume and 6 years of annual crops arranged in 2-year intervals of warm season or cool season crops. The no-till, complex rotation can (1) reduce weed emergence 3- to 4-fold in some annual crops; (2) delay weed emergence 2 to 4 weeks; (3) reduce yield loss due to weed interference; (4) suppress invasion of dandelion into cropland; and (5) enhance soil restoration, improve nutrient cycling, and increase soil porosity. Furthermore, perennial red clover can be converted to no-till cropland with fall mowing; thus, organic producers can include a perennial legume in a no-till rotation. The complex rotation increases the impact of no-till on weed seed decay in soil and provides numerous opportunities for cover crops to replace tillage for controlling weeds. These benefits suppress weed growth and interference such that organic producers may be able to continuously no-till in their farming systems, thus accruing restoration of soil health and long-term sustainability gained with no-till. [ABSTRACT FROM AUTHOR]

Cover crop benefits include nitrogen accumulation and retention, weed suppression, organic matter maintenance, and reduced erosion. Organic farmers need region-specific information on winter cover crop performance to effectively integrate cover crops into their crop rotations. Our research objective was to compare cover crop seeding mixtures, planting dates, and termination dates on performance of rye (Secale cereale L.) and hairy vetch (Vicia villosa Roth) monocultures and mixtures in the maritime Pacific Northwest USA. The study included four seed mixtures (100% hairy vetch, 25% rye-75% hairy vetch, 50% rye-50% hairy vetch, and 100% rye by seed weight), two planting dates, and two termination dates, using a split-split plot design with four replications over six years. Measurements included winter ground cover; stand composition; cover crop biomass, N concentration, and N uptake; and June soil NO3--N. Rye planted in mid-September and terminated in late April averaged 5.1 Mg ha-1 biomass, whereas mixtures averaged 4.1 Mg ha-1 and hairy vetch 2.3 Mg ha-1. Delaying planting by 2.5 weeks reduced average winter ground cover by 65%, biomass by 50%, and cover crop N accumulation by 40%. Similar reductions in biomass and N accumulation occurred for late March termination, compared with late April termination. Mixtures had less annual biomass variability than rye. Mixtures accumulated 103 kg ha-1 N and had mean C:N ratio <17:1 when planted in mid-September and terminated in late April. June soil NO3--N (0 to 30 cm depth) averaged 62 kg ha-1 for rye, 97 kg ha-1 for the mixtures, and 119 kg ha-1 for hairy vetch. Weeds comprised less of the mixtures biomass (20% weeds by weight at termination) compared with the monocultures (29%). Cover crop mixtures provided a balance between biomass accumulation and N concentration, more consistent biomass over the six-year study, and were more effective at reducing winter weeds compared with monocultures. [ABSTRACT FROM AUTHOR]

The use of crop residues for bioenergy production needs to be carefully assessed because of the potential negative impact on the level of soil organic carbon (SOC) stocks. The impact varies with environmental conditions and crop management practices and needs to be considered when harvesting the residue for bioenergy productions. Here, we defined the sustainable harvest limits as the maximum rates that do not diminish SOC and quantified sustainable harvest limits for wheat residue across Australia's agricultural lands. We divided the study area into 9432 climate-soil (CS) units and simulated the dynamics of SOC in a continuous wheat cropping system over 122 years (1889 - 2010) using the Agricultural Production Systems sIMulator (APSIM). We simulated management practices including six fertilization rates (0, 25, 50, 75, 100, and 200 kg N ha−1) and five residue harvest rates (0, 25, 50, 75, and 100%). We mapped the sustainable limits for each fertilization rate and assessed the effects of fertilization and three key environmental variables - initial SOC, temperature, and precipitation - on sustainable residue harvest rates. We found that, with up to 75 kg N ha−1 fertilization, up to 75% and 50% of crop residue could be sustainably harvested in south-western and south-eastern Australia, respectively. Higher fertilization rates achieved little further increase in sustainable residue harvest rates. Sustainable residue harvest rates were principally determined by climate and soil conditions, especially the initial SOC content and temperature. We conclude that environmental conditions and management practices should be considered to guide the harvest of crop residue for bioenergy production and thereby reduce greenhouse gas emissions during the life cycle of bioenergy production. [ABSTRACT FROM AUTHOR]

Fuel ethanol production from lignocellulosic materials is at a level where commercial biofuel production is becoming a reality. The solubilization of the hemicellulose fraction in lignocellulosic-based feedstocks results in a large variety of sugar mixtures including xylose. However, allowing xylose fermentation in yeast that normally is used for fuel ethanol production requires genetic engineering. Moreover, the efficiency of lignocellulosic pretreatment, together with the release and generation of inhibitory compounds in this step, are some of the new challenges faced during second generation ethanol production. Successful advances in all these aspects will improve ethanol yield, productivity and titer, which will reduce the impact on capital and operating costs, leading to the consolidation of the fermentation of lignocellulosic biomass as an economically feasible option for the production of renewable fuels. Therefore the development of yeast strains capable of fermenting a wide variety of sugars in a highly inhibitory environment, while maintaining a high ethanol yield and production rate, is required. This review provides an overview of the current status in the use of xylose-engineered yeast strains and describes the remaining challenges to achieve an efficient deployment of lignocellulosic-based ethanol production. [ABSTRACT FROM AUTHOR]

Companion crops supply additional economic returns when used to establish perennial forage crops, and they should provide similar benefits when establishing native perennial grasslands for bioenergy. We evaluated the effect of cereal grains and native perennial companion crops on biomass yield of three different bioenergy crop types (switchgrass ( Panicum virgatum (L.) Vitman) monoculture, four-species native grass mixture, and CP-25 polyculture mixture) during the seeding year and two subsequent harvest years at four environments. Effects of companion crops on bioenergy crop yields were inconsistent across locations and time, but some general patterns were observed. Averaged across all bioenergy crops, three companion cropping treatments-oat ( Avena sativa L.), barley ( Hordeum vulgare L.), and Canada wildrye ( Elymus canadensis L.) harvested for forage-produced harvestable biomass during the seeding year while suppressing weeds and maintaining perennial biomass yield of the main crop during the first harvest year. Harvestable forage yields were greater for the oat companion crop compared to Canada wildrye during the seeding year at two environments, which could make the cereal grain companion crops more profitable for producers, depending on biomass markets. The polyculture crop yielded 33 and 39 % more perennial biomass than the switchgrass and grass mix in one environment and had 25 % less weed biomass compared to switchgrass in another. No individual companion crop/bioenergy crop combination consistently yielded more perennial biomass or less weed biomass compared to unweeded controls across all environments; however, companion crops can supply marketable grain and biomass during the seeding year when planted with native perennial grasslands without decreasing perennial biomass yields in subsequent harvest years. [ABSTRACT FROM AUTHOR]

A study was conducted in a large pistachio farm in Madera County, California, to assess the spatial variability in water status and irrigation needs by using high-resolution thermal imagery acquired by an unmanned aerial system. We determined the Crop Water Stress Index (CWSI) of two fields, 130 ha each, based on canopy temperature measurements of individual tree crowns, thus assessing the spatial variations in tree water status within each field. The CWSI of each potential management unit (sectors encompassing about 175 trees) was then calculated and related to the days since last irrigation (DSLI) in F1 and F2. The relationship between CWSI and DSLI was established to calculate the average CWSI corresponding to the whole area that was irrigated on the same day. This value was afterward compared with the actual CWSI value of each management unit as a proxy of the spatial variability in CWSI. This information was used to calculate the deviation of each irrigation unit from the fixed irrigation schedule for the whole fields. Our results show that it is feasible to use high-resolution thermal imagery for integrating the crop response in irrigation performance assessment and for providing recommendations at the farm scale. [ABSTRACT FROM AUTHOR]

Long-term agricultural development and cultivation conversions affect soil heavy metal balance and the regional environmental safety. In this study, heavy metal parameters were used to identify changes in soil properties in response to land use and cultivation conversions. The integrated soil quality index, which involves seven heavy metal indices, was proposed to assess the environmental risk of long-term human activities in Northeast China. We used the remote sensing and geographical data for the four-term land use distribution from 1979 to 2009 to identify the spatial patterns of regional land use conversions. Then, 41 samples from the top 20 cm of the soil at sites corresponding to these seven types of conversions were collected (permanent dry land, dry land converted from wetland, dry land converted from forest, permanent wetland, permanent forest, paddy land converted from dry land, and paddy land converted from wetland). Based on the local soil properties and tillage practices, the following seven heavy metal parameters were employed: Arsenic (As), Cadmium (Cd), Chromium (Cr), Copper (Cu), Nickel (Ni), Lead (Pb), and Zinc (Zn). The conversion of farmland from wetland resulted in an increase in the concentration of Pb and Cr in the soil. In contrast, the concentrations of Zn, Cu, Ni, and Cd decreased when wetland was converted into farmland because the tillage practices washed these heavy metals away. During the conversion of dry land and paddy land to wetland, the levels of Pb increased by approximately 28.6 % and 24.7 %, respectively. Under the same conditions, the concentration of As increased by 32.5 % and 14.1 %, respectively. The integrated index also demonstrated that the farmlands were not contaminated by the heavy metals during long-term agricultural development. [ABSTRACT FROM AUTHOR]

Cellulosic bioenergy production provides opportunities to utilize a range of cropping systems that can enhance the multifunctionality of agricultural landscapes. In a 9-ha field experiment located on fertile land in Boone County, IA, USA, we directly compared a corn-soybean rotation harvested for grain, continuous corn harvested for grain and stover, continuous corn harvested for grain and stover with a rye cover crop, newly reconstructed prairie harvested for biomass and fertilized with nitrogen, and unfertilized newly reconstructed prairie harvested for biomass. Comparisons were made using four performance indicators: harvestable yield, net energy balance ( NEB), root production, and nutrient balances. We found trade-offs among systems in terms of the measured performance indicators. Continuous corn systems were the highest yielding, averaging 13 Mg ha−1 of harvested biomass (grain plus stover), whereas fertilized and unfertilized prairies produced the least harvested biomass at 8.8 and 6.5 Mg ha−1, respectively. Mean NEBs were highest in continuous corn systems at 45.1 GJ ha−1, intermediate in the corn-soybean rotation at 28.6 GJ ha−1, and lowest in fertilized and unfertilized prairies at 11.4 and 10.5 GJ ha−1, respectively. Concomitant with the high yields of the continuous corn systems were the large nutrient requirements of these systems compared to the prairie systems. Continuous corn with rye required three times more nitrogen inputs than fertilized prairie. Root production, on the other hand, was on average seven times greater in the prairie systems than the annual crop systems. On highly fertile soils, corn-based cropping systems are likely to play an important role in maintaining the high productivity of agricultural landscapes, but alternative cropping systems, such as prairies used for bioenergy production, can produce substantial yield, require minimal externally derived inputs, and can be incorporated into the landscape at strategic locations to maximize the production of other ecosystem services. [ABSTRACT FROM AUTHOR]

Given the growing global population, mankind must find new ways to lower competition for land between food and fuel production. Our findings for cassava suggest that this important crop can substantially increase the combined production of both food and fuel. Cassava stems have previously been overlooked in starch and energy production. These food-crop residues contain about 30% starch (dry mass) mostly in the xylem rather than phloem tissue. Up to 15% starch of the stem dry mass can be extracted using simple water-based techniques, potentially leading to an 87% increase in global cassava starch production. The integration of biofuel production, using residues and wastewater from starch extraction, may bring added value. The cassava roots on which biofuels and other products are based can be replaced by cassava stems without land use expansion, making root starch available as food for additional 30 million people today. [ABSTRACT FROM AUTHOR]

Maize- and prairie-based systems were investigated as cellulosic feedstocks by conducting a 9 ha side-by-side comparison on fertile soils in the Midwestern United States. Maize was grown continuously with adequate fertilization over years both with and without a winter rye cover crop, and the 31-species reconstructed prairie was grown with and without spring nitrogen fertilization. Both maize stover and prairie biomass were harvested in the fall. We compared amounts of cellulosic biomass produced and harvested, carbohydrate contents as measured by both dietary and detergent methods, and estimated cellulosic ethanol yields per hectare. From 2009-2013, the cropping system with the largest non-grain biomass yield was fertilized prairie, averaging 10.4 Mg ha year aboveground biomass with average harvest removals of 7.8 Mg ha year. The unfertilized prairie produced 7.4 Mg ha year aboveground biomass, with average harvests of 5.3 Mg ha year. Lowest cellulosic (non-grain) biomass harvests were obtained from continuous maize systems, averaging 3.5 Mg ha year when grown with, and 3.7 Mg ha year when grown without a winter rye cover crop, respectively. Unfertilized prairie biomass and maize stover had equivalent dietary-determined potential biomass ethanol yields at 330 g ethanol kg dry biomass, but fertilized prairie was lower at 315. The detergent method did not accurately capture these differences. Over the five-year period of the experiment, unfertilized and fertilized prairie systems averaged 810 and 1,790 L potential cellulosic ethanol ha year more than the maize systems, respectively. Differences in harvested biomass accounted for >90 % of ethanol yield variation. [ABSTRACT FROM AUTHOR]