• Authors:
    • Myllys, M.
    • Sheehy, J.
    • Regina, K.
  • Source: Article
  • Volume: 20
  • Issue: 8
  • Year: 2015
  • Summary: Cultivated organic soils are a remarkable source of greenhouse gases (GHG) in many countries. Keeping the ground water table as high as possible could lower the mineralization rate of the peat and thus the emissions of carbon dioxide (CO2) and nitrous oxide (N2O) from these soils. We studied the effect of raised water table on the emissions of N2O, CO2 and methane (CH4) from undisturbed peat soil profiles of six different Finnish cultivated organic soils during a 5-week outdoor mesocosm experiment. The aim was to determine an optimum water table that would enable grass cultivation but lower the net gas balance of the soil. Raised water table decreased the GHG emissions from each peat type ranging from weakly decomposed Sphagnum peat to highly humified Carex peat. Based on the results, the optimum water table would be 30 cm below the soil surface. The average reduction of the total net emissions with a raise of water table from a typical drainage depth of 70 to 30 cm was 42 % in the outdoors mesocosm experiment and 23 % at a constant temperature (+6 A degrees C). The emissions of both CO2 and N2O declined and the net consumption of CH4 changed to net production as the water table rose. The results were confirmed by long-term measurements at one of the sampled sites. As a conclusion, we see that promoting drainage systems enabling raising of the ground water table and cultivation of crops capable of producing good yields also in wet conditions would be beneficial for the GHG mitigation in agriculture.
  • Authors:
    • Pikula, D.
    • Faber, A.
    • Syp, A.
  • Source: Plant Soil Environ.
  • Volume: 61
  • Issue: 10
  • Year: 2015
  • Summary: The study presents the impact of management practices on greenhouse gas emissions (GHG) and nitrogen (N) losses calculated with a denitrification-decomposition model. Two cropping systems were analysed. The first rotation (A) consisted of potato, winter wheat, spring barley and corn. The second (B) included potato, winter wheat, spring barley and clover with grasses mixture. In A1 and B1 scenarios, fluxes were estimated on the basis of mineral fertilizers input, whereas in A2 and B2 scenarios the assessment of emissions was made with regards to manure. The results indicated that the application of manure in A rotation led to the increase of nitrous oxide (N 2O) emission, N leaching, N surplus, crop yields, and the decrease of nitrogen use efficiency higher than in B rotation. Additional doses of manure in A2 scenario increased the potential of the accumulation of soil organic carbon (SOC) and global warming potential (GWP) by 157%. In B2 scenario, SOC augmented more than three-fold but GWP increased only by 10%. The N losses and GHG emissions could be minimised by controlling N application through the implementation of nutrient management plan in which N doses are defined based on the crop needs and soil quality.
  • Authors:
    • Gleason, R.
    • Finocchiaro, R.
    • Tangen, B.
  • Source: Science of the Total Environment
  • Volume: 533
  • Year: 2015
  • Summary: Wetland restoration has been suggested as policy goal with multiple environmental benefits including enhancement of atmospheric carbon sequestration. However, there are concerns that increased methane (CH4) emissions associated with restoration may outweigh potential benefits. A comprehensive, 4-year study of 119 wetland catchments was conducted in the Prairie Pothole Region of the north-central U.S. to assess the effects of land use on greenhouse gas (GHG) fluxes and soil properties. Results showed that the effects of land use on GHG fluxes and abiotic soil properties differed with respect to catchment zone (upland, wetland), wetland classification, geographic location, and year. Mean CH4 fluxes from the uplands were predictably low (<0.02 g CH4 m(-2) day(-1)), while wetland zone CH4 fluxes were much greater (<0.001-3.9 g CH4 m(-2) day(-1)). Mean cumulative seasonal CH4 fluxes ranged from roughly 0-650 g CH4 m(-2), with an overall mean of approximately 160 g CH4 m(-2). These maximum cumulative CH4 fluxes were nearly 3 times as high as previously reported in North America. The overall magnitude and variability of N2O fluxes from this study (<0.0001-0.0023 g N2O m(-2) day(-1)) were comparable to previously reported values. Results suggest that soil organic carbon is lost when relatively undisturbed catchments are converted for agriculture, and that when non-drained cropland catchments are restored, CH4 fluxes generally are not different than the pre-restoration baseline. Conversely, when drained cropland catchments are restored, CH4 fluxes are noticeably higher. Consequently, it is important to consider the type of wetland restoration (drained, non-drained) when assessing restoration benefits. Results also suggest that elevated N2O fluxes from cropland catchments likely would be reduced through restoration. The overall variability demonstrated by this study was consistent with findings of other wetland investigations and underscores the difficulty in quantifying the GHG balance of wetland systems. Published by Elsevier B.V.
  • Authors:
    • Vogel, A.
    • Strecker, T.
    • Steinauer, K.
    • Richter, A.
    • Ramirez, N.
    • Pierce, S.
    • Rong, J.
    • HongYan, G.
    • FuXun, A.
    • Tilman, D.
    • Scheu, S.
    • Reich, P.
    • Power, S.
    • Roscher, C.
    • Niklaus, P.
    • Manning, P.
    • Milcu, A.
    • Thakur, M.
    • Eisenhauer, N.
  • Source: Global Change Biology
  • Volume: 21
  • Issue: 11
  • Year: 2015
  • Summary: Soil microbial biomass is a key determinant of carbon dynamics in the soil. Several studies have shown that soil microbial biomass significantly increases with plant species diversity, but it remains unclear whether plant species diversity can also stabilize soil microbial biomass in a changing environment. This question is particularly relevant as many global environmental change (GEC) factors, such as drought and nutrient enrichment, have been shown to reduce soil microbial biomass. Experiments with orthogonal manipulations of plant diversity and GEC factors can provide insights whether plant diversity can attenuate such detrimental effects on soil microbial biomass. Here, we present the analysis of 12 different studies with 14 unique orthogonal plant diversity * GEC manipulations in grasslands, where plant diversity and at least one GEC factor (elevated CO 2, nutrient enrichment, drought, earthworm presence, or warming) were manipulated. Our results show that higher plant diversity significantly enhances soil microbial biomass with the strongest effects in long-term field experiments. In contrast, GEC factors had inconsistent effects with only drought having a significant negative effect. Importantly, we report consistent non-significant effects for all 14 interactions between plant diversity and GEC factors, which indicates a limited potential of plant diversity to attenuate the effects of GEC factors on soil microbial biomass. We highlight that plant diversity is a major determinant of soil microbial biomass in experimental grasslands that can influence soil carbon dynamics irrespective of GEC.
  • Authors:
    • Lehmann, J.
    • Vanek, S.
  • Source: Plant and Soil
  • Volume: 395
  • Issue: 1/2
  • Year: 2015
  • Summary: Background and aims: We sought to understand biochar's role in promoting plant phosphorus (P) access via arbuscular mycorrhizas (AM), focusing on whether P solubility and biochar-P proximity altered AM enhancement of P uptake in a mycorrhizal crop legume. Methods: A greenhouse study compared feedstock-derived P with 50 mg P pot -1 of sparingly soluble FePO 4 (Fe-P) or soluble NaH 2PO 4 (Na-P) at different proximities to biochar (co-pyrolyzed, mixed with biochar, mixed with soil) on Phaseolus vulgaris P uptake, specific root length (SRL), AM colonization, AM neutral lipids, and microbial biomass-P. Results: Biochar increased AM colonization by 6% ( p2*) with AM hyphae. Biochar-P proximity did not alter P uptake, but shifted uptake towards AM for Fe-P and roots for Na-P. Soluble P located on biochar increased total plant+microbial P ( p<0.05). Biochar reversed ( p<0.05) reductions in SRL induced by AM. Conclusions: Biochar enhanced AM's access to sparingly soluble P, and root/microbial access to soluble P. Biochar augments sparingly soluble P uptake at scales larger than biochar particles, perhaps by reducing P sorption or facilitating root/hyphal exploration.
  • Authors:
    • Wilkens,S.
    • Weimer,P. J.
    • Lauer,J. G.
  • Source: Agronomy Journal
  • Volume: 107
  • Issue: 6
  • Year: 2015
  • Summary: Full-season corn ( Zea mays L.) hybrids take advantage of more of the growing season than shorter-season hybrids often leading to greater grain and biomass yield. Many agronomic experiments aimed at corn stover production have been performed at forage harvest rather than later when stover is normally harvested for biofuel measurements. The objective of this research was to evaluate the influence of hybrid relative maturity (days RM) on stover ethanol production, ruminant digestibility, and biomass composition. Hybrids selected were high-yielding commercial grain hybrids grown throughout Wisconsin and ranged from 85 to 115 d RM in 10 d RM increments during 2009, and in 5 d RM increments during 2010. Hybrids were harvested at physiological maturity or after a killing frost. Overall, stover and theoretical ethanol yields increased as RM increased at a linear rate of 0.211 Mg ha -1 RM -1 and 67.1 L ha -1 RM -1. Stover nutritional and biomass composition improved as RM increased, but yield variability was greater than nutritional and biomass compositional variability. Increasing ethanol yields will likely occur by increasing stover yields rather than by altering stover composition. Therefore, until price premiums for stover composition are made available to farmers for ethanol production, the adoption of full-season or longer maturing hybrids should be implemented for increased stover and ethanol yields.
  • Authors:
    • Leps, J.
    • Blazek, P.
  • Source: Article
  • Volume: 211
  • Year: 2015
  • Summary: The recent population declines of annual hemiparasitic Rhinanthus species may be a result of changes in mowing dates associated with the intensification of grassland management, but the causal mechanisms are not well understood. We aimed to determine the dynamics of Rhinanthus regeneration after cutting and of fruit ripening under silage or hay making. Mowing was simulated on several dates from mid-May to mid-July in populations of a vernal ecotype of Rhinanthus minor and an aestival ecotype of Rh. alectorolophus. Survival and regeneration of clipped plants, as well as fruit ripening were monitored in the experiments. We showed that Rhinanthus species were capable of resprouting, albeit with high mortality, but only in early spring before the lower leaves were shed. The time of fruit ripening differed among phenological types by over a month and a considerable number of fruits ripened during hay making. If meadows are mown in the period when plants are not able to regenerate and not enough fruits have ripened, Rhinanthus populations could undergo a massive decline. Postponing the first cut until fruits start to ripen is necessary for the protection of these species. Current Czech agri-environmental measures (AEMs) subsidize postponing the first cut only in protected areas, which limits the distribution of Rhinanthus. Moreover, the earliest date for a postponed cut is mid-July, which is too late considering forage quality. We suggest implementing a late-June mowing, which would diversify the mosaic of various mowing dates within protected areas, and could be widely acceptable for farmers in non-protected landscapes.
  • Authors:
    • Joyce, B. L.
    • Baxter, H. L.
    • Cantrell, C. L.
    • Gawde, A.
    • Burkhardt, A.
    • Stewart, C. N.
    • Zheljazkov, V. D.
  • Source: Journal
  • Volume: 44
  • Issue: 6
  • Year: 2015
  • Summary: The Powder River Basin in Wyoming and Montana contains the United States' largest coal reserve. The area produces large amounts of natural gas through extraction from water-saturated coalbeds. Determining the impacts of coalbed natural gas-produced efflux water on crops is important when considering its potential use as supplemental irrigation water. We hypothesized that coalbed natural gas water, because of its high salinity and sodicity, would affect plant secondary metabolism (essential oils) and biomass accumulation. A 2-yr field study was conducted in Wyoming to investigate the effects of produced water on two traditional bioenergy feedstocks - corn ( Zea mays L.) and switchgrass ( Panicum virgatum L.) - and four novel biofuel feedstock species - spearmint ( Mentha spicata L.), Japanese cornmint ( Mentha canadensis L.), lemongrass ([ Cymbopogon flexuosus (Nees ex Steud.) J.F. Watson]), and common wormwood ( Artemisia vulgaris L.). The four nontraditional feedstock species were chosen because they contain high-value plant chemicals that can offset production costs. Essential oil content was significantly affected by coalbed natural gas water in lemongrass and spearmint. Oil content differences between two spearmint harvests in the same year indicated that there were significant changes between the growth stage of the plant and essential oil content; the first harvest averaged 0.42 g of oil per 100 g biomass while the second harvest (harvested before flowering) yielded only 0.19 g oil per 100 g dry biomass. Results indicated that produced water can be used for short-period (2 yr) irrigation of crops. However, prolonged use of untreated produced water for irrigation would likely have deleterious long-term effects on the soil and plants unless the water was treated or diluted (mixed) with good-quality water.
  • Authors:
    • Robertson, G.
    • Tang, J.
    • Cui, M.
    • Gelfand, I.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 212
  • Issue: December 2015
  • Year: 2015
  • Summary: Climate change is causing the intensification of both rainfall and droughts in temperate climatic zones, which will affect soil drying and rewetting cycles and associated processes such as soil greenhouse gas (GHG) fluxes. We investigated the effect of soil rewetting following a prolonged natural drought on soil emissions of nitrous oxide (N 2O) and carbon dioxide (CO 2) in an agricultural field recently converted from 22 years in the USDA Conservation Reserve Program (CRP). We compared responses to those in a similarly managed field with no CRP history and to a CRP reference field. We additionally compared soil GHG emissions measured by static flux chambers with off-site laboratory analysis versus in situ analysis using a portable quantum cascade laser and infrared gas analyzer. Under growing season drought conditions, average soil N 2O fluxes ranged between 0.2 and 0.8 g N m -2 min -1 and were higher in former CRP soils and unaffected by nitrogen (N) fertilization. After 18 days of drought, a 50 mm rewetting event increased N 2O fluxes by 34 and 24 fold respectively in the former CRP and non-CRP soils. Average soil CO 2 emissions during drought ranged from 1.1 to 3.1 mg C m -2 min -1 for the three systems. CO 2 emissions increased ~2 fold after the rewetting and were higher from soils with higher C contents. Observations are consistent with the hypothesis that during drought soil N 2O emissions are controlled by available C and following rewetting additionally influenced by N availability, whereas soil CO 2 emissions are independent of short-term N availability. Finally, soil GHG emissions estimated by off-site and in situ methods were statistically identical.
  • Authors:
    • Lamb, J. A.
    • Fassbinder, J.
    • Baker, J. M.
  • Source: BioEnergy Research
  • Volume: 7
  • Issue: 2
  • Year: 2014
  • Summary: Corn stover removal, whether for silage, bedding, or bioenergy production, could have a variety of environmental consequences through its effect on soil processes, particularly N2O production and soil respiration. Because these effects may be episodic in nature, weekly snapshots with static chambers may not provide a complete picture. We adapted commercially available automated soil respiration chambers by incorporating a portable N2O analyzer, allowing us to measure both CO2 and N2O fluxes on an hourly basis through two growing seasons in a corn field in southern Minnesota, from spring 2010 to spring 2012. This site was part of a USDA multilocation research project for five growing seasons, 2008-2012, with three levels of stover removal: zero, full, and intermediate. Initially in spring 2010, two chambers were placed in each of the treatments, but following planting in 2011, the configuration was changed, with four chambers installed on zero removal plots and four on full removal plots. The cumulative data revealed no significant difference in N2O emission as a function of stover removal. CO2 loss from the full removal plots was slightly lower than that from the zero removal plots, but the difference between treatments was much smaller than the amount of C removed in the residue, implying loss of soil carbon from the full removal plots. This is consistent with soil sampling data, which showed that in five of six sampled blocks, the SOC change in the full removal treatments was negative relative to the zero removal plots. We conclude that (a) full stover removal may have little impact on N2O production, and (b) while it will reduce soil CO2 production, the reduction will not be commensurate with the decrease in fresh carbon inputs and, thus, will result in SOC loss.