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Zurich, Switzerland

Leifeld J.,ART Agroscope Reckenholz Tanikon
Agriculture, Ecosystems and Environment

Organic farming is supposed to be environmentally friendly due to abandonment of external inputs such as mineral fertilizers or pesticides. Albeit conversion to organic farming frequently comes along with a decline in crop yields, proponents of organic farming emphasize the sustainability of that system particularly because of improving organic matter-related soil quality. Based on recent research on mechanisms driving soil organic matter turnover, however, it rather appears that low-input agro ecosystems may convert to smaller efficiency in terms of substrate use by heterotrophs which may affect soil organic matter storage in the long run. A compilation of field data confirms an inferior use efficiency in some organic soils and thus questions the claim of an overall sustainable use of the soil resource in organic farming systems. © 2012 Elsevier B.V. Source

Prasuhn V.,ART Agroscope Reckenholz Tanikon

Long-term field monitoring of soil erosion by water was conducted on arable land in the Swiss midlands. All visible erosion features in 203 fields were continuously mapped and quantified over 10years. The eroded soil volume associated with linear erosion features was calculated by measuring the length and cross-sectional area in rills at representative positions and the extent of interrill erosion was estimated. Averaged across the 10 study years, just under one-third (32.2%) of the fields exhibited erosion. With 0.75t ha-1 yr-1 (mean) and 0.56t ha-1 yr-1 (median), the average annual soil loss of the region was relatively small. The year-to-year variation in soil loss of the region was great and ranged from 0.16 to 1.83t ha--1 yr-1. The maximum annual soil erosion in a single field was 96t yr-1 or 58t ha-1 yr-1, thus demonstrating that only a few erosion events on a few fields may decisively contribute to the total extent of soil erosion in a region. Linear and interrill erosion accounted for 75% and 25% of total soil loss, respectively. Wheel tracks, furrows, headlands, and slope depressions were important on-site accelerators of erosion. Run-on from adjacent upslope areas was an important trigger of erosion. Of the soil moved by erosion, 52% was deposited within the field of origin. A high proportion (72%) of the linear erosion features caused off-site damage. Part of the total eroded soil (20%) was transported into water, thereby contributing to their contamination. The long-term field assessment of soil erosion helps to fill existing knowledge gaps concerning temporal and spatial variability of soil erosion on arable land, the extent and severity of soil erosion and its sources and causes, as well as subsequent off-site damage. © 2010 Elsevier B.V. Source

Van Der Heijden M.G.A.,ART Agroscope Reckenholz Tanikon | Van Der Heijden M.G.A.,VU University Amsterdam

Nutrient loss from ecosystems is among the top environmental threats to ecosystems worldwide, leading to reduced plant productivity in nutrient-poor ecosystems and eutrophication of surface water near nutrient-rich ecosystems. Hence, it is of pivotal importance to understand which factors influence nutrient loss. Here it is demonstrated that arbuscular mycorrhizal (AM) fungi, widespread soil fungi that form mutualistic relationships with the majority of land plants, reduce nutrient loss from grassland microcosms during raininduced leaching events. Grassland microcosms with AM fungi lost 60% less phosphorus and 7.5% less ammonium compared to control microcosms without AM fungi. Similar results were obtained for microcosms planted with each of three different grass species. In contrast, nitrate leaching was not affected by AM. fungi but depended on the amount of nutrients supplied to the microcosms. Moreover, fertilization of the microcosms reduced the abundance of AM fungi and their ability to reduce phosphorus leaching losses. Extrapolation of these results suggests that the disruption of the mycorrhizal symbiosis is one of the reasons for enhanced phosphorus loss from fertilized ecosystems. The microcosms contained a sandy soil, a soil type vulnerable to leaching losses. The reduction of phosphorus leaching by AM fungi may, therefore, represent an upper limit. Advantages and limitations of the experimental setup for assessing the impact of AM fungi on nutrient cycling are discussed. The results indicate that AM fungi contribute to ecosystem sustainability by promoting a closed phosphorus cycle and reducing phosphorus leaching losses. © 2010 by the Ecological Society of America. Source

Desaules A.,ART Agroscope Reckenholz Tanikon
Environmental Monitoring and Assessment

Concern that human impacts on the environment may be harmful to natural resources such as soils as well as to living conditions is the major motivation for long-term environmental monitoring. However, the evidence that measurement bias is not constant through time affects time series as an artifact; this also holds true for chemical soil monitoring. Measurement instabilities occur along the whole measurement chain, from soil sampling to the expression of results. The first step in controlling measurement instability is to identify its relevant sources, and the second is to control it by stabilizing, minimizing, or quantifying measurement instability. For all five steps in the measurement process, from soil sampling to the expression of the analytical results, sources of measurement instability are identified and measures of control discussed, leading to the main conclusion concerning the requirement to continuously control the relevant environmental and measurement boundary conditions that may affect measurement instability. The innovative aspect of this paper consists in explicitly addressing measurement instability in chemical soil monitoring and tracking it along the whole measurement chain. The paper is also a plea for a change of paradigm in long-term environmental monitoring, namely to consider temporal measurements as unstable unless their degree of stability is traceably demonstrated, adequately quantified, and included in interpretation. © 2011 Springer Science+Business Media B.V. Source

Spiess E.,ART Agroscope Reckenholz Tanikon
Nutrient Cycling in Agroecosystems

Intensification of Swiss agriculture after 1950 led to an increase in productivity and a range of environmental and health problems provoked by growing inputs of nitrogen (N), phosphorus (P) and potassium (K) into the agricultural cycle. In 2008, farm-gate balances showed surpluses of 108 kg N ha-1, 5.5 kg P ha-1 and 28 kg K ha-1 for Swiss agriculture. Nutrient surpluses rose between 1975 and 1980 and then decreased significantly until 2008, with percentage reductions being higher for P (80%) and K (54%) than for N (27%). The introduction of direct payments for ecological programmes such as integrated production in 1993 led to a more pronounced decrease in nutrient surpluses for several years, until most farmers had joined these programmes. Lower surpluses could primarily be attributed to reductions in mineral fertilizer use and N deposition. Biological N fixation and atmospheric deposition contributed most to the uncertainty in calculating nutrient balances. N cycle was characterized by substantial inputs into and outputs out of the agricultural sector, whereas P and K cycles were more closed. In future, nutrient balances at a regional level are required to identify areas with high surpluses. In Switzerland, a further reduction in surpluses could be achieved by better feeding strategies and an improved fertilizer management, mainly of animal manure. © 2011 Springer Science+Business Media B.V. Source

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