An understanding of agroecosystems is key to determining effective farming systems. Here we report results from a 21-year study of agronomic and ecological performance of biodynamic, bioorganic, and conventional farming systems in Central Europe. We found crop yields to be 20% lower in the organic systems, although input of fertilizer and energy was reduced by 34 to 53% and pesticide input by 97%. Enhanced soil fertility and higher biodiversity found in organic plots may render these systems less dependent on external inputs.

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It has been suggested that conversion to organic farming contributes to soil carbon sequestration, but until now a comprehensive quantitative assessment has been lacking. Therefore, datasets from 74 studies from pairwise comparisons of organic vs. nonorganic farming systems were subjected to metaanalysis to identify differences in soil organic carbon (SOC). We found significant differences and higher values for organically farmed soils of 0.18 ± 0.06% points (mean ± 95% confidence interval) for SOC concentrations, 3.50 ± 1.08 Mg C ha −1 for stocks, and 0.45 ± 0.21 Mg C ha −1 y −1 for sequestration rates compared with nonorganic management. Metaregression did not deliver clear results on drivers, but differences in external C inputs and crop rotations seemed important. Restricting the analysis to zero net input organic systems and retaining only the datasets with highest data quality (measured soil bulk densities and external C and N inputs), the mean difference in SOC stocks between the farming systems was still significant (1.98 ± 1.50 Mg C ha −1 ), whereas the difference in sequestration rates became insignificant (0.07 ± 0.08 Mg C ha −1 y −1 ). Analyzing zero net input systems for all data without this quality requirement revealed significant, positive differences in SOC concentrations and stocks (0.13 ± 0.09% points and 2.16 ± 1.65 Mg C ha −1 , respectively) and insignificant differences for sequestration rates (0.27 ± 0.37 Mg C ha −1 y −1 ). The data mainly cover top soil and temperate zones, whereas only few data from tropical regions and subsoil horizons exist. Summarizing, this study shows that organic farming has the potential to accumulate soil carbon.climate change | soil quality | agricultural systems

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Consumers have become more aware of healthy and safe food produced with low environmental impact. Organic agriculture is of particular interest in this respect, as manifested by 5.768 million hectares managed pursuant to Council Regulation (EEC) 2092/91 in Europe. However, there can be a considerable risk that the avoidance of chemical inputs in organic farming will result in poor food quality. Here the results of a study on the quality of wheat (Triticum aestivum L.) grown in a 21 year agrosystem comparison between organic and conventional farming in central Europe are reported. Wheat was grown in a ley (grass/clover) rotation. The 71% lower addition of plant-available nitrogen and the reduced input of other means of production to the organic field plots led to 14% lower wheat yields. However, nutritional value (protein content, amino acid composition and mineral and trace element contents) and baking quality were not affected by the farming systems. Despite exclusion of fungicides from the organic production systems, the quantities of mycotoxins detected in wheat grains were low in all systems and did not differ. In food preference tests, as an integrative method, rats significantly preferred organically over conventionally produced wheat. The findings indicate that high wheat quality in organic farming is achievable by lower inputs, thereby safeguarding natural resources.

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In this study the influence of different farming systems on microbial community structure was analyzed using soil samples from the DOK long-term field experiment in Switzerland, which comprises organic (BIODYN and BIOORG) and conventional (CONFYM and CONMIN) farming systems as well as an unfertilized control (NOFERT). We examined microbial communities in winter wheat plots at two different points in the crop rotation (after potatoes and after maize). Employing extended polar lipid analysis up to 244 different phospholipid fatty acids (PLFA) and phospholipid ether lipids (PLEL) were detected. Higher concentrations of PLFA and PLEL in BIODYN and BIOORG indicated a significant influence of organic agriculture on microbial biomass. Farmyard manure (FYM) application consistently revealed the strongest, and the preceding crop the weakest, influence on domain-specific biomass, diversity indices and microbial community structures. Esterlinked PLFA from slowly growing bacteria (k-strategists) showed the strongest responses to long-term organic fertilization. Although the highest fungal biomass was found in the two organic systems of the DOK field trial, their contribution to the differentiation of community structures according to the management regime was relatively low. Prokaryotic communities responded most strongly to either conventional or organic farming management.