17 research outputs found
Nitrogen Budgets and Soil Nitrogen Stocks of Organic and Conventional Cropping Systems: Trade-Off between Efficiency and Sustainability of Nitrogen Use
Organic and conventional cropping systems differ in the nature and amounts of nitrogen (N) inputs, which may affect efficiency and sustainability of N use. In the DOK (bio-Dynamic, bio-Organic, Konventionell) field experiment, organic and conventional cropping systems have been compared since 1978 at two fertilization levels. Nitrogen inputs via manure and/or mineral fertilizers, and N exports from plots with harvested products have throughout been recorded. For all treatments, N outputs with harvests have exceeded the inputs with fertilizers. Over the past years, symbiotic N2 fixation by soybean and clover grown in the trial has additionally been assessed, indicating average annual inputs of about 100 kg ha-1 yr-1 of N fixed from the atmosphere. Soil surface budgets opposing N inputs via fertilization, symbiotic fixation, seeds and deposition to N outputs via harvested products have been computed at the plot level for the duration from 1985 to 2012. The resulting balances range from negative values of about -20 kg N ha-1 yr-1 (where outputs exceed the sum of said N inputs) to surpluses of about +50 kg N ha-1 yr-1. The budget based N use efficiency (NUE; N output via harvested products divided by sum of N inputs) in the case of negative balances suggests irrationally high NUE (>100%), while positive balances are related to lower NUE for treatments with inputs exceeding outputs. Negative balances, however, indicate soil N mining, while surpluses point to a risk of N losses, and/or N accumulation in the soil. Estimation of soil N stock changes based on yearly total N concentration measurements in the topsoil layer is currently ongoing. Preliminary results suggest that soil N stocks in the topsoil decreased under all treatments more than expected from the N balance, and that positive N balances are needed to maintain topsoil N stocks. An increase in soil N concentration was observed in none of the treatments. In conclusion, the results indicate an efficiency-sustainability trade-off. Treatments with a higher NUE lose more soil stock N than those with a lower NUE. Treatments with lower NUE indicate higher N losses from the studied crop-topsoil system. Sustainable soil N management in addition to organic fertilizer inputs might at this site require reduced soil tillage. The significance of N contained in deeper soil layers, and deep rooting crops in recovering leached N should as well be investigated
Symbiotic N2 fixation by soybean in organic and conventional cropping systems
In organic cropping systems nitrogen (N) often limits agricultural production. N2 fixing
crops present an important option to improve N supply and to maintain soil fertility. We
investigated N2 fixation of soybean in conventional and organic cropping systems. The
study was carried out on a long term field experiment, characterized by unequal
fertilization rates and soil microbial activity for the different systems. We assessed the
proportion of N derived from atmosphere (Ndfa) and the total amount of N
symbiotically fixed (Nfix) using the 15N natural abundance method. Ndfa for soybean
was low, ranging from 24 to 54%. The lowest Ndfa was reported for the exclusively
mineral fertilized, and the highest for the bio-organic cropping system. However, there
were no differences between the farming systems in total amount of N symbiotically
fixed. Irrespective of the cropping system, N withdrawal by harvest was higher than N
input by N2 fixation, meaning that soil N stock was not preserved
Stickstoffausnutzungseffizienz von 15N-markierter SchafsgĂĽlle und 15N-markiertem MineraldĂĽnger in biologisch und konventionell bewirtschafteten Anbausystemen
Nitrogen (N) utilisation by crops has to be improved to minimize losses to the
environment. We investigated N use efficiency of animal manure and mineral fertiliser
and fate of fertiliser N not taken up by crops in a bio-organic (BIOORG) and a
conventional (CONMIN) cropping system of a long-term experiment over three
vegetation periods (wheat-soybean-maize). Microplots received a single application of
15N-labelled slurries or mineral fertiliser. At the end of each vegetation period we
tested whether higher microbial activity and biomass in BIOORG than CONMIN soils
and lower long-term N input level in BIOORG affected use efficiency and fate of
fertiliser N not taken up by crops. In total 41%, 15% and 50% of 15N applied as urine,
faeces and mineral fertiliser was recovered by the three crops. 15N recovered from
originally applied urine, faeces and mineral fertiliser in the topsoil at the end of the
third vegetation period was 19%, 25% and 20%, respectively. Of urine-, faeces- and
mineral fertiliser-15N 40%, 61% and 29% was not recovered by the three crops and in
topsoil suggesting significant transport of 15N-labelled components to deeper soil
layers. BIOORG and CONMIN differed neither in fertiliser N use efficiency by crops
nor in 15N recovery in soil indicating insignificant differences in turnover and utilization
of applied manure N in the bio-organic and conventional cropping system
The SIB Swiss Institute of Bioinformatics' resources: focus on curated databases
The SIB Swiss Institute of Bioinformatics (www.isb-sib.ch) provides world-class bioinformatics databases, software tools, services and training to the international life science community in academia and industry. These solutions allow life scientists to turn the exponentially growing amount of data into knowledge. Here, we provide an overview of SIB's resources and competence areas, with a strong focus on curated databases and SIB's most popular and widely used resources. In particular, SIB's Bioinformatics resource portal ExPASy features over 150 resources, including UniProtKB/Swiss-Prot, ENZYME, PROSITE, neXtProt, STRING, UniCarbKB, SugarBindDB, SwissRegulon, EPD, arrayMap, Bgee, SWISS-MODEL Repository, OMA, OrthoDB and other databases, which are briefly described in this article
La validité scolaire et sociale du Test d'Apprentissage de la Pensée Analogique (TAPA)
Le texte discute la validité scolaire et sociale du Test d'Apprentissage de la Pensée Analogique (TAPA