Conservation at the crop edge. A long-term study of conservation headlands without fertiliser

Baxter, E.T. (2021) Conservation at the crop edge. A long-term study of conservation headlands without fertiliser. Doctoral thesis, Harper Adams University.

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The 2020 Agriculture Bill, which will shape government support for agriculture in the UK for the foreseeable future, has a focus on wider issues beyond direct support for agricultural production. The public has to a large extent identified habitat destruction, increased use of agrochemicals, and landscape-wide structural simplification as unwanted (Tscharntke et al., 2012). The need to address these concerns is reflected in the Bill with an emphasis, although no longer stated on the face of the Bill, of public goods for public money. Exactly how much farmland under positive environmental management is necessary to achieve the desired effect is a vexed question. Smith et al. (2020) considered the amount of uncropped land that should be allocated on farms for “biodiversity”, with figures from a range of studies; from Aebischer and Ewald (2004) advocating 6% for Grey partridge (Perdix perdix – afterwards referred to in this thesis as “partridge”), up to 10% for farmland birds in general (Henderson et al., 2012). Smith et al. (2020) themselves suggested that the value of Ecological Focus areas (EFAs) and similar agri-environment measures could be greatly enhanced by managing desirable arable weeds within crops to achieve a 10% covering. This thesis looks at managing desirable arable weeds in the cropped area at the edge of cereal fields. The overarching research question was “Do wild headlands offer a viable option for arable farmers aiming to integrate biodiversity with production?” The thesis begins with an oversight of current discussion surrounding farmland intensification and considers the solutions introduced under Agri-Environment Schemes (AES) and the rationale behind them. Conservation headlands, one such solution, and their derivative, wild headlands, are discussed in some detail. A detailed description of wild headlands, their origins and their practice, as well as a general introduction to the study site are given in Chapter 2. The thesis then looks at answering three “sub questions” of the overarching research question. The first, “What impact do wild headlands have on above ground biodiversity in the crop edge?” is considered in Chapter 3, which looks at a population over the long term of partridges, an indicator species of ecosystem health on farmland. The population trend was examined and the relationship explored between arable weeds in wild headlands, the host plants for phytophagous invertebrates needed by partridge chicks, and availability of those invertebrates. It was found that brood production remained steady on a farm with wild headlands but declined on adjacent farms without. Chick Survival Rate (CSR) on farms without wild headlands was below the minimum 30% needed to maintain a partridge population, while on the farm with wild headlands, the CSR was over 30%. This was reflected in the availability within wild headlands of the host plants for invertebrates and the invertebrates themselves. The second question “What was the economic cost of implementing wild headlands?” is considered in Chapter 4, which compares crop yield and gross margin in headlands of 82 fields with and without wild headlands in four cereal crops over two years. Yields of cereal crops in wild headlands were about 60% of field yield, but with variation between crops. The savings in fertiliser and sprays on wild headlands made up for the shortfall in some crops in some years, and costs of wild headlands were strongly influenced by output prices and fertiliser costs for individual crops. The third question, “How do wild headlands influence arable seedbanks?” is answered in Chapter 5 by examining seedbanks in 25 fields, some of which have had wild headlands intermittently for 20 years. It was found that after allowing for soil characteristics, wild headlands drove species assemblages with greater species richness, evenness and abundance in fields which had had wild headlands. Also found was that wild headlands could restore seedbank populations of weeds to levels seen in the 1970s, but that herbicides in intervening years had maintained seedbanks within reasonable limits. Finally, in Chapter 6 the conclusions of each chapter were brought together and the costs and environmental benefits of wild headlands and any implications for farming in general, opportunities for further research and future agricultural policy that arose from the study discussed

Item Type: Thesis (Doctoral)
Divisions: Crop and Environment Sciences (to 31.07.20)
Depositing User: Ms Kath Osborn
Date Deposited: 03 Sep 2021 10:12
Last Modified: 03 Sep 2021 10:12

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