Beef cattle production systems are the largest contributors of greenhouse gas (GHG) and ammonia (NH) emissions in the livestock industry. Here, we present the first meta-analysis and integrated assessment of gaseous emissions and mitigation potentials for a typical beef cattle feedlot system, including methane (CH), nitrous oxide (NO), and NH losses from enteric fermentation and manure management based on data from 104 studies. A total of 14 integrated emission factors (EF) and the mitigation efficiencies (ME) of 17 available options were provided. The estimated GHG and NH emissions from the baseline feedlot system were 2786 ± 108 kg carbon dioxide equivalents (CO-eq) per animal unit (AU) per year and 49.1 ± 1.5 kg NH AU year, respectively. Enteric CH fermentation and manure on the feedlot contributed 67.5% and 80.8% of the total system GHG and NH emissions, respectively. The highest ME values were found for lipid additives for enteric CH fermentation and urease inhibitor additives (UI) for NH emissions from manure on the feedlot, being -14.9% ( p < 0.05) and -59.5% ( p < 0.001), respectively. The recommended mitigation combinations of a low-crude-protein (CP) diet and a UI additive for manure on the feedlot could reduce the GHG of the system by 4.9% and NH by 50.9%. The results of this study have important implications for developing sustainable beef cattle feedlot systems from the viewpoint of GHG and NH mitigation.

BackgroundSeedling establishment is a crucial and vulnerable stage in the crop life cycle which determines further plant growth. While many studies are available on salt tolerance at the vegetative stage, the mechanisms and genetic bases of salt tolerance during seedling establishment have been poorly investigated. Here, a novel and accurate phenotyping protocol was applied to characterize the response of seedlings to salt stress in two barley cultivars (Nure and Tremois) and their double-haploid population.ResultsThe combined phenotypic data and existing genetic map led to the identification of a new major QTL for root elongation under salt stress on chromosome 7HS, with the parent Nure carrying the favourable allele. Gene-based markers were developed from the rice syntenic genomic region to restrict the QTL interval to Bin2.1 of barley chromosome 7HS. Furthermore, doubled haploid lines with contrasting responses to salt stress revealed different root morphological responses to stress, with the susceptible genotypes exhibiting an overall reduction in root length and volume but an increase in root diameter and root hair density.ConclusionsSalt tolerance at the seedling stage was studied in barley through a comprehensive phenotyping protocol that allowed the detection of a new major QTL on chromosome 7HS.Electronic supplementary materialThe online version of this article (doi:10.1186/s12863-017-0545-z) contains supplementary material, which is available to authorized users.

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This study aimed to investigate the characteristics of gaseous emission (methane—CH4, carbon dioxide—CO2, nitrous oxide—N2O, nitric oxide—NO, hydrogen sulfide—H2S and sulfur dioxide—SO2) and the conservation of carbon (C), nitrogen (N), and sulfur (S) during cattle manure composting under different aeration strategies. Three aeration strategies were set as C60, C100, and I60, representing the different combinations of aeration method (continuous—C or intermittent—I) and aeration rate (60 or 100 L·min−1·m−3). Results showed that C, N, S mass was reduced by 48.8–53.1%, 29.8–35.9% and 19.6–21.9%, respectively, after the composing process. Among the three strategies, the intermittent aeration treatment I60 obtained the highest N2O emissions, resulting in the highest N loss and greenhouse gas (GHG) emissions when the GHG emissions from power consumption were not considered. Within two continuous aeration treatments, lower aeration rates in C60 caused lower CO2, N2O, NO, and SO2 emissions but higher CH4 emissions than those from C100. Meanwhile, C and N losses were also lowest in the C60 treatment. H2S emission was not detected because of the more alkaline pH of the compost material. Thus, C60 can be recommended for cattle manure composting because of its nutrient conservation and mitigation of major gas and GHG emissions.