Agronomic and genetic assessment of organic wheat performance in England: a field-scale cultivar evaluation with a network of farms

Yield gaps between organic and conventional agriculture raise concerns about future agricultural systems which should reduce external inputs and face an unpredictable climate. In the United Kingdom, the performance gap is especially severe for wheat, that, as a result, has a small and shrinking organic acreage. In organic wheat production, most determinants of crop performance are managed at a rotation level, which leaves cultivar choice as the major decision on a seasonal basis. Yet, conventionally generated cultivar recommendations might be inappropriate to organic farms. Furthermore, uncertainty about field-scale crop performance hinders positive developments of the supply chain of organic grains and seeds. 

Here, we present a field-scale evaluation of winter wheat cultivars, integrated with an agronomic crop performance survey, across a network of organic farms, in which we attempted to integrate elements of cultivar evaluation and of an agronomic survey. The present work started in 2017, as part of the ‘LIVESEED: Boosting organic seed production in Europe’ H2020 EU Project, from a joined initiative between the Organic Research Centre and Organic Arable, a membership-based marketing group set up by organic farmers and active in grain marketing, seed supply and technical support.

The main objective was to raise quantitative evidence on organic wheat performance in real-farm, field-scale conditions, to set the foundations and inform future, more detailed and focused, surveys and experiments. We assessed crop performance under multiple angles, integrating grain yield and grain quality indicators with assessments of crop morphology, weed abundance and community composition during the crop cycle, and tested the three following hypotheses:

1. crop performance can be interpreted based on the climatic patterns of the tillering, stem extension and reproductive phases of the crop cycle;
2. grain yield, quality and weed abundance are affected by cultivar choice;  
3. grain yield and quality, as well as weed abundance and community composition, are affected by the emerging fertility and post-emergence weed management strategies adopted by the farmers

We adopted an incomplete block experimental design, in which every farmer was allocated a subset of cultivars and provided with an adequate quantity of seed to grow in one of their commercial winter wheat fields in adjacent strips wide enough to be easily drilled, managed and harvested with farm machinery according to their farm management practices. Statistical analysis was based on the use of linear mixed-effect models and explored variation across (i) environments, (ii) cultivars and (iii) different management strategies.

The dataset contains the following items:

• 'Sites.csv': Experimental sites descriptions;
• 'Tested_varieties.csv': Description of the tested varieties,
• 'Climatic_patterns.csv': Climatic patterns in each site and year,
• 'Key_raw_data.csv': key and methods description for field data collection;
• 'Raw_data.csv': Raw data;
• 'EMMEANS-by-variety.csv': Estimated marginal means of varieties averaged across year and farm;
• 'EMMEANS_by_environment.csv': Estimated marginal means by environment (farm:year) averaged by variety