Biomass Yield of Warm-Season Grasses Affected by Nitrogen and Harvest Management

Native perennial warm-season grasses (NPWSG) have drawn interest as bioenergy feedstocks due to their high productivity with minimal amounts of inputs under a wide range of environments. Nitrogen fertility and harvest timing are critical management practices when optimizing biomass yield of NPWSG. Our objective was to quantify the impact of N fertilizer rate and timing in combination with harvest timing and frequency on NPWSG yield. Research was conducted in 2014 and 2015 on four field-plot locations in Missouri. The experiment was a split-plot design with three replications where N rate and harvest timing were the main and sub-plot treatments, respectively. Nitrogen rates were 0, 34, 67, and 101 kg N ha–1 with two application timings, all early spring and split N (early spring and following first harvest). Harvest timing included two single (September and November) and two double harvests (June followed by September or November) per year. Delaying harvest until November increased yield across sites. November harvest and N rates ≥67 kg ha–1 improved NPWSG biomass yields. Although N fertilization improved yield, partial factor productivity (PFP) of applied N did not increase with annual N rates \u3e34 kg ha–1. Fertilization at 67 kg ha–1 yr–1 provides an opportunity to maintain a balance between yield and N efficiency. These results demonstrated that N fertilization and harvest management of NPWSG were not always independent, and therefore these practices should be simultaneously considered. For example, early-season harvesting suppressed response to N when the second harvest was not delayed until after frost

Factors Affecting Willingness to Cultivate Switchgrass: Evidence from a Farmer Survey in Missouri

Switchgrass is considered as one of the important feedstocks that can contribute towards the attainment of bioenergy goals set under the Renewable Fuels Standard. Yet, the commercial viability of switchgrass based bioenergy is a much debated topic owing to supply side challenges emanating from limited raw materials. It is therefore critical to understand the crucial role of the farmer by studying the willingness to cultivate switchgrass dedicated for bioenergy. To our knowledge, this is the first survey undertaken to assess the farmer preferences and participation in bioenergy markets after the new administration has assumed office, and provides some important insights. Our analysis reveals that the risk attitudes of farmers have an important bearing on their willingness to cultivate switchgrass. Having prior awareness of switchgrass makes farmers less likely to adopt whereas a preference to cultivate a crop after seeing them on demonstration plots at university extension meetings positively influences willingness decisions. Landholdings under pasture/grazing use and under forest/woodland use increases farmer willingness to cultivate switchgrass. On the other hand, having land under the Conservation Reserve Program, lands that experienced flooding or water stress in recent years, or lands that confront erosion issues did not have a significant influence on farmer willingness. While the inherent uncertainty of the cellulosic bioenergy industry is well known, policies that provide a safety net to protect farmers from the downside are an important issue for farmers who are willing to cultivate switchgrass

Global achievements in sustainable land management

Identification and development of sustainable land management is urgently required because of widespread resource degradation from poor land use practices. In addition, the world will need to increase food production to meet the nutritional needs of a growing global population without major environmental degradation. Ongoing climate change and its impacts on the environment is an additional factor to consider in identifying and developing sustainable land use practices. The objectives of this paper are to: (1) provide a background to the need for sustainable land management, (2) identify some of its major components, and (3) discuss some examples of sustainable land management systems that are being practiced around the world. Some common components of this type of management are: (1) understanding the ecology of land management, (2) maintenance or enhancement of land productivity, (3) maintenance of soil quality, (4) increased diversity for higher stability and resilience, (5) provision of economic and ecosystem service benefits for communities, and (6) social acceptability. Several examples of sustainable land management systems are discussed to illustrate the wide range of systems that have been developed around the world including agroforestry, conservation agriculture, and precision agricultural systems. Improved technology, allowing for geater environmental measurement and for improved access and sharing of information, provides opportunities to identify and develop more sustainable land management practices and systems for the future

Greenhouse gas emissions from riparian systems as affected by hydrological extremes: a mini-review

AbstractIncreasing atmospheric greenhouse gas (GHG) concentrations causes global temperature rising as well as extreme hydrological events. Understanding the effects of climate change-induced severe hydrological events such as flooding and drought on soil properties and subsequent GHG emissions from soil has enabled scientists to optimize different land management and global warming potential mitigation of a system. Flooding and drought dynamics affect soil physicochemical properties and GHG emissions specifically from land use systems that are adjacent to streams like riparian buffers. Drivers of soil GHG emissions and the effect of extreme hydrological events on the GHG flux from riparian systems in three climate zones (Mediterranean, temperate, and tropical/subtropical) were investigated in this review utilizing Web of Science and Scopus databases. Wet soil conditions contribute more to global warming (7.2 Mg CO2eq-C ha−1 h−1) than dry soils (2.1 Mg CO2eq-C ha−1 h−1) in riparian systems. Temperate riparian systems showed the greatest soil N2O emissions (0.7 mg N2O-N m−2 h−1) after flooding events/during wet seasons. The greatest CH4 (12 mg CH4-C m−2 h−1) and CO2 (15.2 g CO2-C m−2 d−1) flux from wet soils were observed in tropical/subtropical riparian systems. Greater soil inorganic N content (NO3- and NH4+) in temperate riparian systems is responsible for the higher soil N2O flux during wet seasons. Intense precipitation events and greater soil carbon content in tropical/subtropical riparian systems contributed to more CO2 and CH4 emissions relative to the temperate and Mediterranean riparian systems

Microbial community diversity and composition across a gradient of soil acidity in spruce-fir forests of the southern Appalachian Mountains

Anthropogenic deposition of sulfur (S) and nitrogen (N) contributes substantially to soil acidity in some forest regions and hence studies have focused on modeling and quantifying depositions in landscapes. The resulting acidity can change the soil chemical balance, nutrient availability, microbial communities, and at a broader scale, ecosystem functioning. In this study, a 16S PCR-DGGE (polymerase chain reaction-denaturing gradient gel electrophoresis) approach was used to measure the bacterial diversity and identify the dominant bacterial species along a soil acidity gradient in high elevation spruce-fir forests of Great Smoky Mountains National Park (GSMNP). Sample sites were selected based upon modeled S deposition class (6-14, 15-23, 23-32, and 33-41kgha -1). Collected soils were analyzed for pH, C, N, Ca, Al, S, CEC, and base saturation. Average soil pH in the O, A, and B horizons were 3.6, 3.6 and 3.9, respectively. Modeled S deposition was found to be an unreliable predictor of soil S content as well as most other soil chemical properties. DGGE profiles of bacterial partial 16S rRNA genes revealed minor differences in bacterial diversity while communities were similar, dominated by members of phylum Actinobacteria, Acidobacteria, Planctomycetes, Proteobacteria, and Chloroflexi. Dominance of acidophilic bacterial species, often found in highly acidic environment such as acid-mine drainage and sphagnum bogs, suggests that the poorly buffered soils that are endemic to southern Appalachian spruce-fir forests are saturated with acidity. Our results suggest that stricter air quality standards have not resulted in shift to less acid-tolerant bacteria. © 2012 Elsevier B.V