Browsing by Author "Ruser, R."

Soil compaction and soil moisture are important factors influencing denitrification and N2O emission front fertilized soils. We analyzed the combined effects of these factors on the emission of N2O, N-2 and CO2 from undisturbed soil cores fertilized with (NO3-)-N-15 (150 kg N ha(-1)) in a laboratory experiment. The soil cores were collected from differently compacted areas in a potato field, i.e. the ridges (rho(D) = 1.03 g cm(-1)), the interrow area (rho(D) = 1.24 g cm(-3)), and the tractor compacted interrow area (rho(D) = 1.64 g cm(-3)), and adjusted to constant soil moisture levels between 40 and 98% water-filled pore space (WFPS). High N2O emissions were a result of denitrification and occurred at a WFPS >= 70% in all compaction treatments. N2 production occurred only at the highest soil moisture level (>= 90% WFPS) but it was considerably smaller than the N2O-N emission in most cases. There was no soil moisture effect on CO2 emission from the differently compacted soils with the exception of the highest soil moisture level (98% WTPS) of the tractor-compacted soil in which soil respiration was significantly reduced. The maximum N2O emission rates from all treatments occurred after rewetting of dry soil. This rewetting effect increased with the amount of water added. The results show the importance of increased carbon availability and associated respiratory O-2 consumption induced by soil drying and rewetting for the emissions of N2O, (c) 2005 Elsevier Ltd. All rights reserved.

Agricultural practices contribute to emissions of the greenhouse gases CO2, CH4 and N2O. The aim of this study was to determine and discuss the aggregate greenhouse gas emission (CO2, CH4 and N2O) from two different farming systems in southern Germany. Farm A consisted of 30.4 ha fields (mean fertilization rate 188 kg N per ha), 1.8 ha meadows, 12.4 ha set-aside land and 28.6 adult beef steers (year-round indoor stock keeping). Farm B followed the principles of organic farming (neither synthetic fertilizers nor pesticides were used) and it consisted of 31.3 ha fields, 7 ha meadows, 18.2 ha pasture, 5.5 ha set-aside land and a herd of 35.6 adult cattle (grazing period 6 months). The integrated assessment of greenhouse gas emissions included those from fields, pasture, cattle, cattle waste management, fertilizer production and consumption of fossil fuels. Soil N2O emissions were estimated from 25 year-round measurements on differently managed fields. Expressed per hectare farm area, the aggregate emission of greenhouse gases was 4.2 and 3.0 Mg CO2 equivalents for farms A and B, respectively. Nitrous oxide emissions (mainly from soils) contributed the major part (about 60%) of total greenhouse gas emissions in both farming systems. Methane emissions (mainly from cattle and cattle waste management) were approximately 25% and CO2 emissions were lowest (circa 15%). Mean emissions related to crop production (emissions from fields, fertilizer production, and the consumption of fossil fuels for field management and drying of crops) was 4.4 and 3.2 Mg CO2 equivalents per hectare field area for farms A and B, respectively. On average, 2.53% of total N input by synthetic N fertilizers, organic fertilizers and crop residues were emitted as N2O-N. Total annual emissions per cattle unit (live weight of 500 kg) from enteric fermentation and storage of cattle waste were about 25% higher for farm A (1.6 Mg CO2 equivalents) than farm B (1.3 Mg CO2 equivalents). Taken together, these results indicated that conversion from conventional to organic farming led to reduced emissions per hectare, but yield-related emissions were not reduced. (C) 2002 Elsevier Science B.V. All rights reserved.

The large temporal variation in nitrous oxide (N2O). methane (CH4) and carbon dioxide (CO2) flux rates is a major source of error when estimating cumulative fluxes of these radiative active trace gases. We developed an automated system for near-continuous, long-term measurements of N2O, CH4 and CO2 fluxes from cropland soils and used it to study the temporal variation of N2O and CH4 fluxes from potato (Solanum tuberosum L.) fields during the crop periods of 1997 and 1998, and also to determine the effects of management practices and weather. Additionally, we evaluated the error of other common methods, namely, weekly or monthly measurements, used for estimating cumulative fluxes. ne fluxes were quantified separately for the ridges, uncompacted interrows and tractor-compacted interrows. Total N2O-N emission from the potato field during the growing period (end of May to September) was 1.6 kg ha(-1) in 1997 and 2.0 kg ha(-1) in 1998; emissions were highest for the tractor-compacted soil. Periods of increased N2O losses were induced by heavy precipitation (in particular in compacted soil) and by the killing of potato tops (on the ridges) by herbicide application. The total CH4-C uptake in the potato field during the growing period was 295 g ha(-1) in 1997 and 317 g ha(-1) in 1998. The major fraction of the total CH, uptake (approximate to 86%) occurred on the ridges. Weekly measurements of N2O fluxes complemented by additional event-related flux determinations provided accurate estimates of total emissions. The monthly flux determination was not adequate for determining the temporal variation of the N2O emission rates. Weekly measurements were sufficient to provide reliable estimates of the cumulative CH4 uptake. (C) 2002 Elsevier Science B.V. All rights reserved.