Purdy, David
(2024)
INVESTIGATING THE BIOPHYSICAL EFFECTS OF THE EXTENDED ROOT PHENOTYPE OF COVER CROPS AND DIFFERENT TILLAGE SYSTEMS ON SOIL HEALTH AND CROP YIELDS.
PhD thesis, University of Nottingham.
Abstract
There is a wide and growing interest in using cover crops and reducing the impacts of tillage within modern sustainable farming practices, which are increasingly supported by UK Government environmental land management schemes (ELMS). Soil and its health are vitally important to modern farming systems and the findings reported in this study show that cover crops can improve soil structure, infiltration rates, lower bulk densities and increase many biological indicators such as worm numbers, microbial biomass and decomposition rates among a large number of other response variables. In addition, after five years, cover crops were shown to sequester and store more soil carbon which is of importance given the heightened interest in their role in climate mitigation. Tillage however, damaged soil structure and made no improvement to infiltration rates or had any impact on biological indicators. The only benefits of tillage were to manage surface compaction when soils dried out in the spring, something that cover crops failed to do, and reduced the impact of excessive residue, both of which can also achieved with shallow low disturbance technology, an approach supported in sustainable farming incentives. Soil chemistry remained predominantly static throughout the study, with tillage perhaps providing some small marginal gains, indicating the main impacts of cover crop and tillage are largely associated with the biological and physical components of soil health. The expectation that cover crops would have a positive impact on yield was less clear, with an increase in yield only manifest in one year of the five, suggesting their more their role is to improve how soil functions. Over the eight harvests within the two replicated trials, tillage provided no positive yield responses. Cover crops played a vital role in the suppression of the weed blackgrass, but the actual mechanism involved was less understood, but it makes them a potentially useful tool to control this difficult to manage weed. Finally, the success or failure of cover crops were largely determined by their management, with the key principles of establishing them promptly after the maincrop and terminating them early proving critical to their success.
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