Torsten Müller

Remediation of copper in vineyards--a mini review.

Viticulturists use copper fungicide to combat Downy Mildew. Copper, a non-degradable heavy metal, can accumulate in soil or leach into water sources. Its accumulation in topsoil has impacted micro and macro organisms, spurring scientists to research in situ copper removal methods. Recent publications suggest that microorganism assisted phytoextraction, using plants and bacteria to actively extract copper, is most promising. As vineyards represent moderately polluted sites this technique has great potential. Active plant extraction and chelate assisted remediation extract too little copper or risk leaching, respectively. However, despite interesting pot experiment results using microorganism assisted phytoextraction, it remains a challenge to find plants that primarily accumulate copper in their shoots, a necessity in vineyards where whole plant removal would be time consuming and financially cumbersome. Vineyard remediation requires a holistic approach including sustainable soil management, proper plant selection, increasing biodiversity and microorganisms.

Modelling water dynamics with DNDC and DAISY in a soil of the North China Plain: A comparative study

The performance of the DNDC and Daisy model to simulate the water dynamics in a floodplain soil of the North China Plain was tested and compared. While the DNDC model uses a simple cascade approach, the Daisy model applies the physically based Richards equation for simulating water movement in soil. For model testing a three years record of the soil water content from the Dong Bei Wang experimental station near Beijing was used. There, the effect of nitrogen fertilization, irrigation and straw removal on soil water and nitrogen dynamics was investigated in a three factorial field experiment applying a split-split-plot design with 4 replications. The dataset of one treatment was used for model testing and calibration. Two other independent datasets from further treatments were employed for validating the models. For both models, the simulation results were not satisfying using default parameters. After parameter optimisation and the use of site-specific van Genuchten parameters, however, the Daisy model performed well. But, for the DNDC model, parameter optimisation failed to improve the simulation result. Owing to the fact that many biological processes such as plant growth, nitrification or denitrification depend strongly on the soil water content, our findings bring us to the conclusion that the site-specific suitability of the DNDC model for simulating the soil water dynamics should be tested before further simulation of other processes.

Substrate inputs, nutrient flows and nitrogen loss of two centralized biogas plants in southern Germany.

In Germany, centralized biogas digestion plants (BGP) have been recently constructed. BGPs purchase the substrates from surrounding farmers and, in return, farmers receive the effluents. Substrate inputs, nutrient inputs and outputs were studied for two BGPs with effluent liquid–solid separation. Additionally, the path of the nitrogen (N) during manure handling was assessed. Silage maize (65–75% of the dry matter (DM) inputs) and grass (ca. 20% of the DM inputs) were the main inputs in both BGPs. During manure handling, it is estimated that 20–25% of the N in the effluents was lost via gaseous N emissions. From an environmental point of view the two main challenges are to reduce these gaseous N losses, and to provide N via the effluents mainly for spring manure application, and less so for autumn application. In solid effluents, gaseous N losses during storage are the main potential N loss pathway, whereas for liquid effluents gaseous N losses during and after field spreading are of great relevance. Current management indicated that approximately 50% of the N in the effluents was available for spring application and approximately 30% in autumn due to cleanout of stores before winter. Calculations show that the use of substrates with high DM content during autumn and winter would reduce the demand for storage capacity, thus reducing the demand for store’s cleanout in autumn. This leads to effluents with higher nutrient concentration that are very suitable for application to spring sown crops. Furthermore, some substrates like cereal grains and grass lead to effluents higher in N, whereas silage maize and other substrates lead to effluents low in N. An adapted substrate management would allow more N for spring application. The cycles of P and K are closed, enabling a complete replenishment of the P and K outputs.

Field measurements of the CO2 evolution rate under different crops during an irrigation cycle in a mountain oasis of Oman

For millennia oasis agriculture has been the backbone of rural livelihood in the desertic Sultanate of Oman. However, little is known about the functioning of these oasis systems, in particular with respect to the C turnover. The objective was to determine the effects of crop, i.e. alfalfa, wheat and bare fallow on the CO 2 evolution rate during an irrigation cycle in relation to changes in soil water content and soil temperature. The gravimetric soil water content decreased from initially 24% to approximately 16% within 7 days after irrigation. The mean CO2 evolution rates increased significantly in the order fallow (27.4 mg C m −2 h −1 ) < wheat (45.5 mg C m −2 h −1 ) < alfalfa (97.5 mg C m −2 h −1 ). It can be calculated from these data that the CO2 evolution rate of the alfalfa root system was nearly four times higher than the corresponding rate in the wheat root system. The decline in CO2 evolution rate, especially during the first 4 days after irrigation, was significantly related to the decline in the gravimetric water content, with r = 0.70. CO2 evolution rate and soil temperature at 5 cm depth were negatively correlated (r =− 0.56, n = 261) due to increasing soil temperature with decreasing gravimetric water content.

Decomposition of plant residues of different quality in soil—DAISY model calibration and simulation based on experimental data

Abstract A parameter setup for the DAISY model calibrated on data measured in the field was evaluated on data obtained from a lab-incubation experiment with residues of leguminous green manure plants, blue grass, rape straw and barley straw. The aim of this study was to test and further develop the principles and parameters for the turnover and the initial characterisation of these plant materials in the DAISY model. The field-calibrated parameter set led to considerable problems when applied to the lab-incubation experiment. For mineral N, soil microbial biomass N and added organic matter, none of the model simulations was fully satisfactory. The only exception was the treatment without addition of plant material. As a consequence, the parameters controlling the turnover of added organic matter and soil microbial biomass have been modified. Further conceptual changes have been suggested. It was not possible to simulate the initial decay and N release from added organic matter (AOM) by simply subdividing it into a water-insoluble part (AOM1) and a water-soluble part (AOM2). However, the C/N ratio and the cellulose content of the added plant residues may be useful indicators for the partitioning of plant materials into a slowly decomposable (AOM1) and a rapidly decomposable (AOM2) part. The general concept of two AOM-pools with predefined constant turnover rates and C/N ratios is questioned for plant residues with very different properties. After addition of easily decomposable green plant materials, death and maintenance respiration rates of modelled soil microbial biomass pools had to be reduced considerably in order to fit simulated mineral N to measured values. This is in contrast to the assumption of two SMB-pools with different but constant properties. After these modifications it was possible to achieve reliable simulations of mineral N, cumulative soil respiration and added organic matter. However, a major problem remained after recalibration. It was not possible to simulate SMB-N satisfactorily in the treatments with red clover, white clover or white melilot. It is concluded that the DAISY model does not fully reflect the flow of N through SMB after addition of easily decomposable leguminous plant materials and the following turnover into soil microbial residual N (SMR-N). The introduction of a separate SMR-pool is proposed.

Effects of setup of centralized biogas plants on crop acreage and balances of nutrients and soil humus

An increasing number of biogas plants (BGPs) based on digestion of dedicated energy crops have been implemented in Germany. The objectives of this study were to assess the changes in (1) the acreage of different crops (silage maize, cereals, etc.) related to the setup of the BGP, (2) nutrient flows and budgets (N, P, K) due to the implementation of the BGPs, and (3) to assess the effluent N in the overall crop N supply. Data from 14 farmers before the setup of the BGPs were compared with data after implementation. Due to the setup of the BGPs, the acreage of silage maize greatly increased and there were significant negative effects on the weighted soil humus budgets, no effects on the weighted mean N and P budgets, and a negative trend regarding the K budgets. Results concerning the N release from organic manuring to maize crops showed that one third of the farmers considerably over-fertilize maize, indicating an underestimation of short- and long-term N supply of manure N. The implementation of centralized BGPs established very intensive nutrient cycles and, in the long-term higher risks of nutrient losses and environmental pollution are expected. One very effective measure to compensate for negative effects on the soil humus budgets and nitrate leaching is an enlargement of cover cropping, which will also offer economic revenue by providing aboveground biomass for digestion. If the amounts of effluents returned to a single farm or field are not adapted to the nutrient composition of the substrates delivered to the BGP, large nutrient imbalances can result. An effective measure to get a better allocation of the available nutrients is a solid-liquid separation of the effluents, enabling a more targeted allocation of the nutrients.

Evaluation of the wick method for in situ 13C and 15N labelling of annual plants using sugar-urea mixtures

To investigate the amount and fate of root-derived C and N, often tracer techniques are used, where plants are labelled with isotopes. In the present study, we evaluated the suitability of the cotton wick method for in situ labelling of peas (Pisum sativum L.) and oats (Avena sativa L.) with 13C and 15N simultaneously. With two greenhouse experiments we investigated how the wick method and aqueous urea and sugar solutions at a variety of concentrations affected plant development. In addition, we investigated the distribution of 13C and 15N in plants from column experiments under outdoor conditions. Solution was taken up by the plant from a small vial connected to the stem by a cotton wick which was passed through a hole in the stem of the plants. Generally, solution uptake varied between individual plants and decreased with increasing sugar concentrations. Below-ground, above-ground and total plant dry matter, were not significantly affected by the wick method and the applied solutions. Mixtures of aqueous glucose solutions at 2 to 4% and aqueous urea solutions at 1% are useful carriers of 13C and 15N. However, in the investigated plants isotopes were not homogeneously distributed among plant parts. Above-ground plant biomass was preferentially enriched with 13C and 15N, whereas below-ground plant biomass was generally lower enriched. Moreover, isotope distribution ratio of individual plants varied considerably, independent of plant part or timing of labelling. This must be taken into account when estimating root-derived C and N. Future studies comparing labelling methods need to present the isotope distribution ratios among plant parts to allow a true comparison of the methods and the evaluation of their suitability for estimating rhizodeposition.

Strengthening learning processes in natural resource management in developing countries through interdisciplinary and problem‐oriented learning

In 1998 three Danish universities developed an interdisciplinary, problem‐oriented curriculum in order to strengthen capacity‐building capabilities in the area of environmental education, training and research at universities and research organisations in Malaysia and Thailand earmarked for environment and development assistance by the Danish government. The programme, which was partly implemented in developing countries as periods of fieldwork, represented important educational innovations. The purpose of this study was to evaluate these activities. The distinct principles forming the educational foundation of the programme were identified. These related to the curriculum organization, the learning tasks and the learning environment. The first step in a cogent evaluation process was to examine how the educational principles were oprerationalized into practical teaching/learning steps. In the next step, they formed the criteria for the evaluation. On the basis of quantitative and qualitative data it was shown that the programme fulfilled the stipulated accademic requirements.

Impact of reduced tillage on greenhouse gas emissions and soil carbon stocks in an organic grass-clover ley - winter wheat cropping sequence

Highlights • First study comparing climate impacts of tillage systems in organic arable farming.• No tillage system impact on N2O and CH4 emissions in grass-clover and wheat.• Higher N2O pulses after tillage operations with increasing soil organic carbon.• Higher soil organic carbon stocks with reduced tillage in slurry fertilised fields.

Cover crops influence soil microorganisms and phytoextraction of copper from a moderately contaminated vineyard

We investigated the ability of summer (Avena sativa [oat], Trifolium incarnatum [crimson clover], Chenopodium [goosefoot]) and winter (Vicia villosa [hairy vetch], Secale Cereale L. [Rye], Brassica napus L. partim [rape]) cover crops, including a mixed species treatment, to extract copper from an organic vineyard soil in situ and the microbial communities that may support it. Clover had the highest copper content (14.3mgCukg(-1) DM). However, it was the amount of total biomass production that determined which species was most effective at overall copper removal per hectare. The winter crop rye produced significantly higher amounts of biomass (3532kgDMha(-1)) and, therefore, removed significantly higher amounts of copper (14,920mgCuha(-1)), despite less accumulation of copper in plant shoots. The maximum annual removal rate, a summation of best performing summer and winter crops, would be 0.033kgCuha(-1)y(-1). Due to this low annual extraction efficiency, which is less than the 6kgCuha(-1)y(-1) permitted for application, phytoextraction cannot be recommended as a general method of copper extraction from vineyards. Copper concentration did not influence aboveground or belowground properties, as indicated by sampling at two distances from the grapevine row with different soil copper concentrations. Soil microorganisms may have become tolerant to the copper levels at this site. Microbial biomass and soil enzyme activities (arylsulfatase and phosphatase) were instead driven by seasonal fluxes of resource pools. Gram+ bacteria were associated with high soil moisture, while fungi seemed to be driven by extractable carbon, which was linked to high plant biomass. There was no microbial group associated with the increased phytoextraction of copper. Moreover, treatment did not influence the abundance, activity or community structure of soil microorganisms.