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Agricultural production systems are affected by complex interactions between social and ecological factors, which are often hard to integrate in a common analytical framework. We evaluated differences in crop production among farms by integrating components of several related research disciplines in a single socio-ecological analysis. Specifically, we evaluated spring barley (Hordeum vulgare, L.) performance on 34 farms (organic and conventional) in two agro-ecological zones to unravel the importance of ecological, crop and management factors in the performance of a standard crop. We used Projections to Latent Structures (PLS), a simple but robust analytical tool widely utilized in research disciplines dealing with complex systems (e.g. social sciences and chemometrics), but infrequently in agricultural sciences. We show that barley performance on organic farms was affected by previous management, landscape structure, and soil quality, in contrast to conventional farms where external inputs were the main factors affecting biomass and grain yield. This indicates that more complex management strategies are required in organic than in conventional farming systems. We conclude that the PLS method combining socio-ecological and biophysical factors provides improved understanding of the various interacting factors determining crop performance and can help identify where improvements in the agricultural system are most likely to be effective.

Many parts of the world are investigating the efficacy of recycling nutrient resources to agriculture from different industry and domestic sectors as part of a more circular economy. The complex nature of recycled products as soil amendments coupled to the large diversity of soil types and their inherent properties make it difficult to optimize the benefits and minimize the risks from potentially toxic elements often present in recycled materials. Here we investigated how wheat grain cadmium (Cd) concentration was affected by soil amendments, namely human urine and biogas digestate compared to traditional farm manures and mineral fertilizers. We show that Cl(-) inadvertently added to soils with e.g. urine or biogas digestate strongly increased crop Cd concentrations, largely by mobilizing inherent soil Cd. This resulted in wheat grain Cd levels that could result in exceeding recommended WHO limits for dietary intake. This was evident even in soils with low inherent Cd content and when Cd inputs were low. The future of a circular economy that helps to underpin global food security needs to ensure that the effects of applying complex materials to different types of agricultural land are fully understood and do not jeopardize food safety., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Element balances are widely used and are incorporated within national action programs to combat nutrient emissions from agriculture to the environment. They rely on data that are readily available at farm-gate and field level, and the information generated is easy to communicate to farmers and policy makers. This may have contributed to high expectations on element balances as a tool for optimising agricultural nutrient use efficiency and thereby reducing nutrient losses. Element balances are potentially useful as a screening tool across Europe provided the methods to calculate them are standardised, their limitations and usefulness defined and appropriate target values are established by which they can be compared. It is difficult to establish straightforward relationships between nutrient management, surplus, losses and environmental impact. Simple farm-gate and field balances need to be complemented by a better understanding of the processes regulating nutrient dynamics, and their spatial and temporal variability. Hence, agronomic and environmental reference or target values need to be established for different production systems, geographical areas and elements. Proper instruments and tools as well as training and educational programmes have to be developed for a successful implementation. [Copyright &y& Elsevier]

Negative potassium (K) balances have been reported from grass-dominated organic systems in several European countries, and in these systems delivery of K from soil primary minerals by weathering is probably crucial to sustained productivity. Mass balances and K budgets have been made at eight grass-dominated experimental agricultural systems, one each in Scotland and Sweden and six in Norway. Where no fertiliser K was applied, the deficits obtained were in the range 35–241 kg K ha−1 per year. An estimate of the weathering rate was determined by the biogeochemical PROFILE model that varied widely between locations (3–82 kg K ha−1 per year). This paper is a first attempt to apply the steady-state PROFILE model on agricultural soils by using data from experimental sites. The Monte Carlo simulation of the weathering rate calculation showed that differences in specific surface area and soil water content strongly influenced the predicted weathering rate, which was associated with a degree of uncertainty. All sites showed a negative annual K-balance, which means that the specific contribution that mineral weathering makes to the long-term replenishment of soil exchangeable-K is important but may not be sufficient to counteract large K removal associated with high crop yields. Despite the uncertainties in the weathering rate calculation, these preliminary results are still useful in several aspects because the simulations make it possible to compare different agroecosystems with different management regimes, climate, soil properties, etc. The simulations also indicate which environmental factors are likely to be the most influential on weathering rates. Soil physical properties, such as moisture content, bulk density and surface area, appeared to be amongst the most important input parameters controlling actual weathering rates within groups of soils having similar mineralogical and chemical compositions. There is now a need for improved laboratory experimental data that better describe the kinetics of mineral weathering in order to enhance the accuracy and precision of PROFILE. [Copyright &y& Elsevier]