Functional Compost

The aim of the research program Functional Compost is to develop and test compost, which have been enriched with chitin, for plant growth promoting properties and to recognise specific mechanisms. Two types of compost were included in the program: source separated biodegradable municipal solid waste compost (DM = 62 %) and garden and park waste compost (DM = 66 %). Chitin was added in trace amounts during the maturity phase, combined with two levels of trace amounts immediately before adding the compost to the growth medium. The research program includes several parallel experiments. In experiment I, compost (20 vol. %) was added to soil (no plants) and incubated at 15 C for 5 month, under regular determination of microbial respiration and gross and net N mineralization. There was a significant increase in respiration due to chitin enrichment, which could not be explained by the amount of C derived from the chitin, which therefore suggest a priming effect. The N analyses are still being processed in the laboratory, but data are expected to be available at the conference. In experiment II, compost was mixed with sand, put into pots in a climate chamber, and spring barley seeds infected with Fusarium culmorum were sown in the pots. After 3 weeks of growth, the health of the plants was determined, and the chitinase activity in the sand was measured. The health of the plants and the chitinase activity was significantly higher in the treatments receiving municipal waste compared to the treatments receiving garden waste compost. However, there was no clear effect of the chitin enrichment. Additionally, the microbial community structure of the two types of compost, with and without early chitin, was determined by Denaturing Gradient Gel Electrophoresis (DGGE). There was a clear separation between compost types, and with or without early chitin amendment. Experiment III is a regular growth experiment, and is running right now. Compost has been incorporated into soil, put into pots in the greenhouse, and spring barley is grown for 2 month before determination for wet and dry weight and N uptake. Data from experiment III is expected to be available at the conference

Østrogener fra human urin i miljøet

Human urin indeholder mange værdifulde næringsstoffer. I stedet for at oprense næringsstofferne fra spildevandet, kan urin med fordel tilbageføres til landbruget som organisk gødning. Samtidig ville man mindske østrogenbelastningen til de meget sårbare vandmiljøer. Men hvordan vil østrogenbelastningen i jord være ved brug af human urin i forhold til almindelige organiske gødninger

Sources of nitrogen for winter wheat in organic cropping systems

In organic cropping systems, legumes, cover crops, residue incorporation, and manure application are used to maintain soil fertility, but the contributions of these management practices to soil nitrogen (N) supply remain obscure. We examined potential sources of N for winter wheat (Triticum aestivum L.) in four experimental cropping systems established in 1997 on three soil types. Three of the four systems were under organic management. Topsoil N, depth of the A horizon, and cumulated inputs of N since 1997 were determined at plot level. Labile soil N pools (mineral N, potentially mineralizable N [PMN], microbial biomass N [MBN]) were monitored during two growth periods; at one site, biomass C/N ratios were also determined. Soil for labile N analysis was shielded from N inputs during spring application to isolate cumulated system effects. PMN and MBN were correlated across all sites and rotations (r2=0.72). The MBN corresponded to 46-85, 85-145 and 74-172 kg N ha-1 at the three sites and differed significantly between cropping systems, but MBN could not explain differences in wheat grain N yields. Instead, a multiple linear regression model explained 76 and 82% of the variation in grain N yields in organic cropping systems in 2007 and 2008, showing significant effects of, respectively, topsoil N, depth of A horizon, cumulated inputs of N, and N applied to winter wheat in manure. Thus, soil properties, and past and current management all contributed to winter wheat N supply

Impacts of zero tillage on soil enzyme activities, microbial characteristics and organic matter functional chemistry in temperate soils

Zero tillage management of agricultural soils has potential for enhancing soil carbon (C) storage and reducing greenhouse gas emissions. However, the mechanisms which control carbon (C) sequestration in soil in response to zero tillage are not well understood. The aim of this study was to investigate the links between zero tillage practices and the functioning of the soil microbial community with regards to C cycling, testing the hypothesis that zero tillage enhances biological functioning in soil with positive implications for C sequestration. Specifically, we determined microbial respiration rates, enzyme activities, carbon source utilization and the functional chemistry of the soil organic matter in temperate well drained soils that had been zero tilled for seven years against annually tilled soils. Zero tilled soils contained 9% more soil C, 30% higher microbial biomass C than tilled soil and an increased presence of aromatic functional groups indicating greater preservation of recalcitrant C. Greater CO2 emission and higher respirational quotients were observed from tilled soils compared to zero tilled soils while microbial biomass was 30% greater in zero tilled soils indicating a more efficient functioning of the microbial community under zero tillage practice. Furthermore, microbial enzyme activities of dehydrogenase, cellulase, xylanase, β-glucosidase, phenol oxidase and peroxidase were higher in zero tilled soils. Considering zero tillage enhanced both microbial functioning and C storage in soil, we suggest that it offers significant promise to improve soil health and support mitigation measures against climate change

Biochar effect on the mineralization of soil organic matter

The objective of this work was to verify whether the addition of biochar to the soil affects the degradation of litter and of soil organic matter (SOM). In order to investigate the effect of biochar on the mineralization of barley straw, soil was incubated with 14C-labelled barley straw with or without unlabelled biochar. To investigate the effect of straw on the mineralization of biochar, soil was incubated with 14C-labelled biochar with or without straw. In addition, to investigate the effect of biochar on old SOM, a soil labelled by applying labelled straw 40 years ago was incubated with different levels of biochar. All experiments had a control treatment, without any soil amendment. The effect of biochar on the straw mineralization was small and nonsignificant. Without biochar, 48±0.2% of the straw carbon was mineralized within the 451 days of the experiment. In comparison, 45±1.6% of C was mineralized after biochar addition of 1.5 g kg-1. In the SOM-labelled soil, the organic matter mineralized more slowly with the increasing doses of biochar. Biochar addition at 7.7 g kg-1 reduced SOM mineralization from 6.6 to 6.3%, during the experimental period. The addition of 15.5 g kg-1 of biochar reduced the mineralized SOM to 5.7%. There is no evidence of increased degradation of either litter or SOM due to biochar addition; consequently, there is no evidence of decreased stability of SOM