Biochar, compost and biochar-compost blend as options to recover nutrients and sequester carbon.

This work assessed the potential environmental impact of recycling organic materials in agriculture via pyrolysis (biochar) and composting (compost), as well its combination (biochar-compost blend) versus business-as-usual represented by mineral fertiliser. Life cycle assessment methodology was applied using data sourced from experiments (FP7 project Fertiplus) in three countries (Spain, Italy and Belgium), and considering three environmental impact categories, (i) global warming; (ii) acidification and (iii) eutrophication. The novelty of this analysis is the inclusion of the biochar-compost blend with a focus on multiple European countries, and the inclusion of the acidification and eutrophication impact categories. Biochar, compost and biochar-compost blend all resulted in lower environmental impacts than mineral fertiliser from a systems perspective. Regional differences were found between biochar, compost and biochar-compost blend. The biochar-compost blend offered benefits related to available nutrients and sequestered C. It also produced yields of similar magnitude to mineral fertiliser, which makes its acceptance by farmers more likely whilst reducing environmental impacts. However, careful consideration of feedstock is required.

Improving national-scale carbon stock inventories using knowledge on land use history.

National-scale inventories of soil organic carbon (SOC) and forest floor carbon (FFC) stocks have a high uncertainty. Inventories are often based on the interpolation of sampled information, often using a number of covariables to help such interpolation. The rationale for the choice of these covariables is not always documented, despite the fact that many local-scale studies have identified the factors explaining spatial variability of SOC and FFC stocks. These studies indicate, among others the importance of long-term land use history. Despite this, information on the effects of land use history has never been used to explain variability of carbon stocks in national-scale inventories. We designed an alternative method to improve national-scale inventories of SOC and FCC for the Dutch sand area that takes stock of the findings of detailed case studies. Determinants for SOC and FFC stocks derived from landscape-scale case studies were used to map national-scale spatial variability and to calculate national totals. The resulting national-scale spatial distribution was compared with the SOC stock map from the current Dutch greenhouse gas inventory. Using land use history to explain SOC variability decreased the error of the SOC stock estimate in 60 % of the area. The error in FFC stocks decreased in half of the forest area after including soil fertility, tree species, and forest age as explanatory factors. Estimates with reduced uncertainty will make land use and land management a more attractive and acceptable mitigation option to reduce emissions of greenhouse gases for the LULUCF sector.

Effect of soil sample preservation, compared to the effect of other environmental variables, on bacterial and eukaryotic diversity.

Archived soil samples are a valuable source for retrospective ecological studies, and their recent analysis using molecular ecological approaches has drawn significant attention within the scientific community. However, the possibility of addressing ecological questions regarding detectable microbiota in dried and extensively stored soils has not yet been fully evaluated. To achieve this, soil samples collected from two long-term grassland experiments in the United Kingdom and The Netherlands were subjected to air-drying at 40-42 degrees C and stored at room temperature. Total bacterial, Bacillus benzoevorans-related and eukaryotic communities associated with these samples were analyzed by DGGE-fingerprinting of PCR-amplified ribosomal RNA gene fragments. Changes in microbial community structure due to drying and storage were evaluated by multivariate analysis in relation to changes caused by other environmental conditions, such as soil pH, type of fertilizer and vegetation. Soil drying and storage affected the detectable community structure, but did not materially impair our capacity to identify the effect of soil parameters studied in long-term grassland experiments. Although, in some cases, the amplitude of the influence of a given parameter changed due to sample preservation, analyses revealed that pH, fertilization and soil type significantly influenced microbial community structure in the analyzed samples.

Gaseous nitrogen and carbon losses from pig manure derived from different diets.

Manipulation of the diets of pigs may alter the composition of the manure and thereby the environmental and agricultural qualities of the manure. Laboratory studies were performed to quantify the effect of manipulation of pig diets on the chemical composition of the derived manure (slurry), the potential emission of methane (CH4) and ammonia (NH3) during anaerobic storage of the manure, and the potential nitrous oxide (N2O) and carbon dioxide (CO2) emission after application of the manure to soil. The diets differed in contents of crude protein and salt (CaSO4), and the type and contents of nonstarch polysaccharides (NSP). Emissions of NH3 and CH4 during storage were smaller at a low than at a high dietary protein content. The emission of NH3 was significantly related to the contents of ammonium (NH4), total N, and pH. The emission of CH4 was significantly related to contents of dry matter, total C, and volatile fatty acids in the manure. The effect of manure composition on N2O emission markedly differed between the two tested soils, which points at interactions with soil properties such as the organic matter content. These types of interactions require soil-specific recommendations for mitigation of N2O emission from soil-applied pig manure by manipulation of the diet. From the tested diets, decreasing the protein content has the largest potential to simultaneously decrease NH3 and CH4 emissions during manure storage and N2O emission from soil. An integral assessment of the environmental and agricultural impact of handling and application of pig manure as a result of diet manipulation provides opportunities for farmers to maximize the value of manures as fertilizer and soil conditioner and to minimize N and C emissions to the environment.