Agricultural Engineering Research, Volume 11 (2005)

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    N2O Release During Cultivation of Energy Crops
    (2005) Hellebrand, Hans Jürgen; Schulz, Volkhard; Kern, Jürgen; Kavdir, Yasemin
    The emission of nitrous oxide (N 2 O) from the soil has a significant impact on the greenhouse gas balance of en- ergy crops. Factors like soil type, temperature, precipitation, tillage practice (annual or perennial crop), and level of fertilisation can affect the source strength of N2 O emissions and fertiliser-induced N2 O emissions. The N2 O-fluxes from different sites of an experimental field were measured using the flux chamber method in combi- nation with gas chromatography. The sites had three nitrogen fertilisation levels (0 kg N ha-1 y-1, 75 kg N ha-1 y-1, and 150 kg N ha-1 y-1). The soil nitrate concentration was determined by ion chromatography. The mean of an- nually accumulated emission of N2 O-N from all measuring spots was 1.4 kg N2 O-N ha-1 y-1. The accumulated emissions varied between 0.5 kg N2 O-N ha-1 y-1 to 3.8 kg N2 O-N ha-1 y-1 depending on fertilisation level, crop variety, and year. The mean annually fertiliser-induced N2 O-N emission from all fertilised sites was 0.7 % for the period from 1999 to 2004. This mean nitrogen conversion factor (ratio of N2 O-N emission to fertiliser-N in- put) ranged from 0.2 to 1.6 %. The mean conversion factor for perennial crops was lower (0.4 % for both fer- tilisation levels of 75 and 150 kg N ha-1 y-1) than that for annual crops (0.7 % for 75 kg N ha-1 y-1 and 0.9 % for 150 kg N ha-1 y-1). Several enhanced N2 O emission spots with maxima of up to 1400 μg N2O m-2 h-1 were ob- served at sites with the higher level of nitrogen fertilisation, lasting for several weeks, in the course of the meas- urements. These local peak emissions were mainly responsible for the raise of the nitrogen conversion factor of sites fertilised with 150 kg N ha-1 y-1 compared to sites with fertilisation level of 75 kg N ha-1 y-1. Although N2O emissions doubtless depend on nitrogen fertilisation and tillage, it could be shown that also climate has a strong effect on N2 O emissions. In contrast to a low correlation between N2 O emissions and soil nitrate concentration, N2 O emissions are relatively close correlated to annual precipitation.
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    Infrared Imaging for Plant Protection
    (2005) Hellebrand, Hans Jürgen; Dammer, Karl-Heinz; Beuche, Horst; Herppich, Werner B.; Flath, Kerstin
    Fungi infections, which may cause variations of plants’ surface tem- perature, can be recognised by infrared cameras in the thermal range (MIR: λ = 8-12 μm) under laboratory conditions. In the field, pro- nounced natural temperature variations of several Kelvin within the crop canopy prevent the recognition of infected plants by commercial thermal vision systems as stand-alone solutions. Near infrared cam- eras ( λ = 0.9-1.7 μm) fitted with band-pass filters show different inten- sity distributions of the reflected radiation. The evaluation of the spec- tral intensity relations improves the differentiation. By NIR several im- portant contents (H 2 O, sugars, acids, etc.) of the surface tissue cells are measured, whereas thermography determines the plant transpiration.
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    Opportunities and Challenges of a Real-Time Control of Seeding Depth
    (2005) Knappenberger, Thorsten; Köller, Karlheinz
    A variation of seeding depth did not play any role in agricultural appli- cation. Modern spacing drills offer the possibility for a mechanical change of the seeding depth but it is scarcely used as the user does not know on what the setting should rely on. Changing soils and topo- graphic variations are responsible for different water contents in the top soil layer. A simulation model for corn is supposed to include spa- tial viability. Through variation of seeding depth it allows to establish uniform conditions for germination.
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    Development of a Data Base System for the Evaluation of Biogas Tests : Data Management and Quantification of Methodological Effects
    (2005) Schlattmann, Markus; Speckmaier, Manfred; Gronauer, Andreas
    Results of fermentation-tests can show significant spreads due to different experimental methods. This leads to uncertainties in calculation, planning and understanding of anaerobic process-kinetics. In order to gather de- tailed data of fermentation-tests, a databank-based software relating high-resolution data was developed. The software was used to assess differences in the results of fermentation-tests arising from the application of differ- ent methods. The gas-yields calculated from data logged hourly were not significantly different from those cal- culated on a daily basis. The deviations between calculated theoretic gas-yields and the results of semi- continuous tests were less than 10 %. Batch and semi-continuous tests with the same base substrate led to simi- lar results which may be due to synergistic effects. The pH-values measured immediately after sampling were 0.25 units lower than determined in the laboratory analysis.
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    Influence of Organic Matter on the Efficiency of Membranes
    (2005) Reimann, Winfried; Kern, Jürgen
    Large amounts of wastewater derive from the food industry. Water recycling by means of membrane tech- nology may offer promising cost savings, although it might involve some problems. Wastewater deriving from the treatment of fruits and vegetables, the processing of milk, and the slaughtering of cattle and sheep can be highly polluted by dissolved organic compounds. The higher the organic load expressed as chemical oxygen demand (COD), the lower the treatment efficiency is. High COD of the wastewater results in reduced filtrate flux and permeate flux of the membranes for microfiltration, ultrafiltration and reverse osmosis, and also re- duces the selectivity of the membranes for reverse osmosis. In order to upgrade dairy farm wastewater with a COD of 984 mg/l, microfiltration combined with reverse osmosis is sufficient to guarantee the limiting values for discharge into surface waters and to obtain a water quality which allows reuse as process water. The treat- ment of slaughterhouse wastewater (COD = 1,737 mg/l), however, requires a second stage of re-verse osmosis. The results of this study represent benchmarks, which may be utilised for long-term studies on a technical scale in order to design full-scale equipment.