Abstract
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 UK, 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. The relation between crop performance and climatic patterns is explored, to capitalise past growing seasons in cultivar and management decisions on-farm. Grain yield and grain protein content were linked by a dual relation, positive across environments and negative across cultivars. Feed-grade cultivars showed a relatively high yield (4.5–5.5 t/ha) but low protein (8.5–9.3%), whereas breadmaking and historic cultivars showed higher protein (10.4–11.1%) and lower yields (3.5–4.0 t/ha). Historic phenotypes showed better weed suppressive ability than modern ones, without trade-offs with yield or quality. Multiple regressions showed that weed abundance at wheat anthesis was the main yield predictor. The effects of two different post-emergence weed management strategies were observed. Farms relying on interrow hoeing showed lower weed abundance, but a higher relative abundance of the dominant species than that of those relying on spring tine harrowing. Future wheat breeding and cultivar testing should account for crop-weed relations, weed management strategies and their effects on nutrient use efficiency. Further data collection can inform plant breeding on critical traits for low-input farming and shed light on cultivar-environment-management interactions.
Highlights
Organic crop production shows a yield and temporal stability gap (Knapp and van der Heijden 2018) compared to conventional agriculture
Based on our evidence of (i) weed abundance as a key determinant of grain yield, of (ii) differences in weed abundance and community composition between the two main weed management systems observed, and of (iii) cultivar differences in weed suppressive ability, in terms of dynamic stability of the trait, we suggest that post-emergence weed management strategy could be a key descriptor to differentiate crop management systems to explore genotype-bymanagement interactions
This work described the field-scale performance of organic winter wheat cultivars across a network of organic farms, combining aspects of an agronomic survey and of a decentralised cultivar evaluation
Summary
Organic crop production shows a yield and temporal stability gap (Knapp and van der Heijden 2018) compared to conventional agriculture. The yield advantage of conventional crop production relies on external inputs that fulfil crop nutrient requirements (mineral fertilisers) and alter the relationship between crops and the natural flora (herbicides), fauna (pesticides) and microbiota (e.g. fungicides). Such buffering of environmental variation is increasingly challenging in conventional farming as well, especially as environments become more unpredictable under climate change. Wheat is the most important British arable crop in terms of acreage, covering 1,797 million ha in 2018. Wheat organic acreage has been steeply declining during the past decade and only covered 0.5% of the
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