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CROPSYS
Objectives
The overall goal is to quantify productivity and environmental impacts of different organic and conventional cropping systems across a range of soil and climatic conditions, and to identify management measures which contribute significantly to a sustainable development of the individual cropping systems. The basic hypothesis is that organic cropping systems can be maintained with high productivity at low environmental impact through better crop rotation design and management, as modified by soil type and climate. This will be achieved through a better description of the role of soil N dynamics, soil properties and crop and weed dynamics in the different systems, and using modelling and scenario analyses to integrate and evaluate production-related and environmental indicators of sustainability.
Background
Modern agricultural systems greatly influence the environment, and there is a particular emphasis in Denmark on nitrate leaching and greenhouse gas emissions from agriculture. Sustainable agricultural systems also need to fulfil the requirements for quantity and quality of the agricultural produce. Crop production in organic farming systems relies to a large extent on soil fertility for nutrient supply. The soil fertility must be maintained via choice of crop rotation and (green) manuring practices. A proper management of this to improve crop yields and reduce emissions to the environment requires an in-depth understanding of soil processes and nutrient dynamics, and their effects on crops and weeds.
A long-term organic crop rotation (CRO) experiment was initiated in 1997 at three different locations in Denmark; in 2005 it is modified to include also a conventional system. The three locations represent typical soils (sand, loamy sand and sandy loam) and climates for Danish agriculture. The design of the currently 8-year old rotations allows for effects of manure application and catch crops to be distinguished, and for effects of soil type and climate to be quantified. Thus, a differentiated analysis of management strategies can be conducted. The project will exploit this unique long-term experiment for an integrated study of the productivity and nitrogen (N) flows in organic cropping systems.
The project will quantify productivity and environmental impacts of different organic and conventional cropping systems across a range of soil and climatic conditions, and identify management measures, which contribute significantly to a sustainable development of the individual cropping systems. This will be achieved through an integrated experimental and modelling programme, where measurements of key indicators of productivity and environmental impact and of the underlying processes and dynamic soil properties are carried out in the CRO experiment. A simulation model (FASSET) and a life cycle analysis (LCA) model will be used to analyse different management scenarios. The output of the work is guidelines for improving the sustainable development of organic crop production systems in Denmark.
Role of individual workpackages
WP1 will coordinate the project and ensure the communication between partners and with stakeholders. A common measurement and management protocol for the CRO experiment will be maintained. All data from the CRO experiment will be stored in a database for access by all partners.
WP2 will manage the CRO experiment. The experiment includes three 4-year crop rotations representing an organic green manure/cash crop rotation, an organic cash crop rotation and a conventional cash crop rotation. A factorial design is used, which includes two manure treatments and two catch crops treatments. With two replicate plots for each system combination, a total of 64 field plots are managed at each site. Crop yield and biomass of crops and weeds will be measured. The crop N uptake will be measured and the N 2 -fixation will be measured in legume crops and catch crops.
WP3 will measure nitrate leaching of all cropping systems of the CRO experiment. This enables an interpretation of short- and long-term effects of management and location on the nitrate leaching. The leaching of dissolved organic nitrogen (DON) will be measured in a campaign coordinated with measurements of topsoil DON in WP5. The potential uptake of N by roots in soil layers below the installed suction cups will be analysed from measurements of root development using minirhizotrons and modelling (WP6).
WP4 will measure nitrous oxide emissions from four selected treatments in the CRO experiment during a 12 month period at two of the locations. Samples of the topsoil will be taken at the sandy loam site to investigate cropping systems effects on denitrification and the ratio of N 2 O:N 2 production. Soil samples will be collected in autumn 2008 at two depths for measurements of total carbon (C) and N to analyse trends in soil C and N storage.
WP5 will quantify the effects of contrasting cropping systems on a range of soil attributes (including pore size distribution, air permeability, soil workability, soil mineral N, DON, microbial biomass N). Measurements will be taken during two years in the CRO experiment. Some of the measurements will be taken in all systems. However, the majority of the effort will focus on the four contrasting systems and the two sites also used in WP4. In addition, soil samples will be analysed for net N mineralisation and for microbial biomass pools.
WP6 will use statistical methods, simulation modelling (FASSET) and life cycle analyses (LCA) to generalise the results of the CRO experiment (WP2 to WP5) to other climatic and soil conditions and to other management strategies. This will include an assessment of the environmental impact of the whole product chain for both organic and conventional farming systems. These results will be used for quantifying management measures that may contribute significantly to a sustainable development of organic farming systems.