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Nitrogen Budgets and Soil Nitrogen Stocks of Organic and Conventional Cropping Systems: Trade-Off between Efficiency and Sustainability of Nitrogen Use

Oberson, Astrid; Jarosch, Klaus A.; Bosshard, Christine; Dubois, David; Frossard, Emmanuel; Hammelehle, Andreas; Mäder, Paul and Mayer, Jochen (2018) Nitrogen Budgets and Soil Nitrogen Stocks of Organic and Conventional Cropping Systems: Trade-Off between Efficiency and Sustainability of Nitrogen Use. In: Abstract Book - ESA2018. XVe European Society for Agronomy Congress (ESA), 27.-31.8.2019, Geneva, Switzerland, p. 44.

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Online at: http://www.esa-congress-2018.ch/programme/programme-and-abstract-book/

Summary

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.


EPrint Type:Conference paper, poster, etc.
Type of presentation:Paper
Keywords:cropping system, nitrogen use efficiency, nutrient budget, soil nitrogen stock, nitrogen loss, organic cropping
Subjects:"Organics" in general
Soil > Soil quality
Crop husbandry > Soil tillage
Research affiliation: Switzerland > FiBL - Research Institute of Organic Agriculture Switzerland > Soil Sciences
Switzerland > Agroscope
Switzerland > ETHZ - Agrarwissenschaften
Germany > Federal States > Hessen > Landesbetrieb Landwirtschaft Hessen
Switzerland > Other organizations
Deposited By: Mäder, Paul
ID Code:34559
Deposited On:18 Feb 2019 15:03
Last Modified:18 Feb 2019 19:50
Document Language:English
Status:Published
Refereed:Not peer-reviewed

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