The Rothamsted Long-Term Experiments: A Continuing Resource for Agriculture and Environmental Research for over 170 Years.

Agro-ecological research began at Rothamsted in 1843 when the first of the “Classical” field experiments was established by Lawes and Gilbert. Some of these experiments still continue and form part of the Rothamsted Long-Term Experiments National Capability. The best known are the Broadbalk Wheat Experiment (started 1843), Hoosfield Spring Barley Experiment (started 1852) and Park Grass Continuous Hay experiment (started 1856). Initial research focussed on the value of fertilisers and manures for crop production, but, over time, the experiments have been modified to include the use of lime, herbicides, fungicides, new crop varieties and higher N rates to ensure they remain relevant to current agricultural issues, whilst also maintaining their long-term integrity. About 300 000 samples of dried plant and soil material, collected from the experiments since the 1840’s, are stored in the Rothamsted Sample Archive. Data collected from the experiments are stored in the electronic Rothamsted Archive (e-RA www.era.rothamsted.ac.uk).

In addition to studies on crop yields and their trends over time, the experiments have been used for numerous other topics including:

• Soil carbon and nitrogen turnover
• Impacts of organic carbon content on soil physical properties
• Plant species diversity in semi-natural grassland
• Trends in micronutrient concentrations of wheat grain and implications for human nutrition
• Plant gene expression in relation to different manuring regimes
• Soil metagenomics
• Crop pathogen diversity and atmospheric sulphur deposition
• Fungicide resistance in plant pathogens
• Weed population dynamics in arable cropping

In the Broadbalk Experiment grain yields of winter-sown wheat have been surprisingly insensitive to soil organic carbon content provided sufficient nutrients are applied as inorganic fertilizers. But the opposite is the case for spring-sown barley in the Hoosfield Experiment. With modern spring barley varieties, well protected from fungal diseases, maximum yields are only obtained where soil organic carbon content has been increased through long-term application of manure.