Nitrogen-neutrality: a step towards sustainability

We propose a novel indicator measuring one dimension of the sustainability of an entity in modern societies: Nitrogen-neutrality. N-neutrality strives to offset Nr releases an entity exerts on the environment from the release of reactive nitrogen (Nr) to the environment by reducing it and by offsetting the Nr releases elsewhere. N-neutrality also aims to increase awareness about the consequences of unintentional releases of nitrogen to the environment. N-neutrality is composed of two quantified elements: Nr released by an entity (e.g. on the basis of the N footprint) and Nr reduction from management and offset projects (N offset). It includes management strategies to reduce nitrogen losses before they occur (e.g., through energy conservation). Each of those elements faces specific challenges with regard to data availability and conceptual development. Impacts of Nr releases to the environment are manifold, and the impact profile of one unit of Nr release depends strongly on the compound released and the local susceptibility to Nr. As such, Nneutrality is more difficult to conceptualize and calculate than C-neutrality. We developed a workable conceptual framework for N-neutrality which was adapted for the 6th International Nitrogen Conference (N2013, Kampala, November 2013). Total N footprint of the surveyed meals at N2013 was 66 kg N. A total of US$ 3050 was collected from the participants and used to offset the conference’s N footprint by supporting the UN Millennium Village cluster Ruhiira in South- Western Uganda. The concept needs further development in particular to better incorporate the spatio-temporal variability of impacts and to standardize the methods to quantify the required N offset to neutralize the Nr releases impact. Criteria for compensation projects need to be sharply defined to allow the development of a market for N offset certificates Online supplementary data available from stacks.iop.org/ERL/9/115001/mmediainfo:eu-repo/semantics/publishedVersio

Root contributions to long-term storage of soil organic carbon: theories, mechanisms and gaps

The depth to which plants locate their roots has important but yet poorly understood implications with regard to the profile distribution and dynamics of soil organic carbon (SOC). We compared the profile distribution of fine root biomass (FRB) with depth distribution of SOC, based on data recalculated from published literature. Mechanisms through which roots might contribute to long-term storage of SOC were reviewed. There was general agreement across previous studies that over 60% of SOC were in the top 0.3 m of soil, where FRB was concentrated. However, studies in which depth distribution of SOC was simultaneously compared to profile distribution of RB were not readily available, suggesting that this area of research has received limited attention. There is a paucity of empirical evidence to lend support to theorised mechanisms through which roots stabilise SOC. The relationship between profile distribution of roots and depth distribution of SOC must be evaluated on-site for defined landuses. A standardised format for presenting results must be developed and agreed upon to ease interpretation of the results. National Soil Science Societies may have a significant role in this process and this 19th World Congress of Soil Science will be an opportune assembly for dialogue

Plant Root Contributions to Carbon Sequestration on the Northern Tablelands of New South Wales, Australia

Root contributions to the soil carbon (C) budget vary depending on botanical composition, land-use and management, soil characteristics and prevailing environmental and climatic conditions. How these factors interact to influence the distribution of C and nitrogen (N) stocks with soil depth is not well understood. A two-phased study was conducted to evaluate root contributions to depth distribution of C and N stocks in an Alfisol on the Northern Tablelands of New South Wales (NSW), Australia. Phase 1 evaluated the impact of land-use on: (i) distribution of fine root biomass and associated root functional traits to a maximum depth of 1.0 m, (ii) accumulation of root and soil C and N stocks within the 1.0 m soil profile in relation to the root traits investigated and (iii) decomposability of root litters from improved pastures, native pastures and woodlands. In phase II, a one-year field experiment was conducted to address objectives (i) to (iii) above under three native grasses of NSW: 'Austrodanthonia richardsonii' (C3 sun-adapted), 'Chloris ventricosa' (C4 sun-adapted) and 'Microlaena stipoides' (C3 shade-adapted) across growing seasons at 0% and 75% shading

How Safe is Chicken Litter for Land Application as an Organic Fertilizer?: A Review

Chicken litter application on land as an organic fertilizer is the cheapest and most environmentally safe method of disposing of the volume generated from the rapidly expanding poultry industry worldwide. However, little is known about the safety of chicken litter for land application and general release into the environment. Bridging this knowledge gap is crucial for maximizing the benefits of chicken litter as an organic fertilizer and mitigating negative impacts on human and environmental health. The key safety concerns of chicken litter are its contamination with pathogens, including bacteria, fungi, helminthes, parasitic protozoa, and viruses; antibiotics and antibiotic-resistant genes; growth hormones such as egg and meat boosters; heavy metals; and pesticides. Despite the paucity of literature about chicken litter safety for land application, the existing information was scattered and disjointed in various sources, thus making them not easily accessible and difficult to interpret. We consolidated scattered pieces of information about known contaminants found in chicken litter that are of potential risk to human, animal, and environmental health and how they are spread. This review tested the hypothesis that in its current form, chicken litter does not meet the minimum standards for application as organic fertilizer. The review entails a meta-analysis of technical reports, conference proceedings, peer-reviewed journal articles, and internet texts. Our findings indicate that direct land application of chicken litter could be harming animal, human, and environmental health. For example, counts of pathogenic strains of Eschericia coli (105–1010 CFU g−1) and Coliform bacteria (106–108 CFU g−1) exceeded the maximum permissible limits (MPLs) for land application. In Australia, 100% of broiler litter tested was contaminated with Actinobacillus and re-used broiler litter was more contaminated with Salmonella than non-re-used broiler litter. Similarly, in the US, all (100%) broiler litter was contaminated with Eschericia coli containing genes resistant to over seven antibiotics, particularly amoxicillin, ceftiofur, tetracycline, and sulfonamide. Chicken litter is also contaminated with a vast array of antibiotics and heavy metals. There are no standards set specifically for chicken litter for most of its known contaminants. Even where standards exist for related products such as compost, there is wide variation across countries and bodies mandated to set standards for safe disposal of organic wastes. More rigorous studies are needed to ascertain the level of contamination in chicken litter from both broilers and layers, especially in developing countries where there is hardly any data; set standards for all the contaminants; and standardize these standards across all agencies, for safe disposal of chicken litter on land