Date of Award
Master of Science
Grant L Thompson
Tillage radish (Raphanus sativus L.) has been utilized as a cover crop for alleviating soil compaction and scavenging nutrients in agricultural crop productions systems. Recognizing the improvements of compacted soils from a tillage radish cover crop in agricultural cropping systems and the need for compaction remediation in post-construction urban soils where landscape plants will be established, we sought to test the potential of tillage radish for post-construction applications. Unlike the more predictable seasonal periods of sewing, terminating, and incorporating a tillage radish cover crop in an annual agricultural crop rotation, the timing and environmental conditions of building and landscape construction is more variable, which may have an effect on cover crop radish seed germination. In the first study, a simulated landscape system in a controlled environment was used to evaluate the performance of tillage radish (Raphanus sativus L. ‘Nitro’) at five soil compaction levels and the impacts of that cover crop on the growth of the following establishment of a model herbaceous perennial – coral bells (Heuchera micrantha var. diversifolia (Rydb.) Rosend., Buttters & Lakela ‘Purple palace’). Radishes produced comparable amounts of mean aboveground and belowground dry biomass through a range of compacted soils but showed reduced mean biomass at the highest soil compaction level. Coral bells following the no radish control treatment produced more aboveground dry mean biomass than coral bells following the cold termination radish treatment, which is speculated to be a result of allelopathic effects and/or nutrient unavailability. The findings of this study provides evidence that tillage radishes have the capacity to grow successfully at a range of soil bulk densities, but more work is needed better understand the management considerations for adapting agricultural cover crops, such as tillage radish, for use in ornamental landscapes and in post-construction soils. The aim of the second study was to determine the germination of different tillage radish cultivars at a range of temperatures and water conditions that may be experienced throughout the growing season if tillage radish was used in a construction setting. Our study utilized a modified international seed testing protocol and controlled environment growth chambers to quantify the percent germination of five tillage radish cultivars across eight air temperatures and four water amounts. We found that air temperature significantly affected the germination percentage across all cultivars, and the optimal range for germination was 23-33 ℃. Water amount significantly affected the germination of Nitro, Smart, and Badger radish cultivars, suggesting that irrigation management during the germination of these cultivars may be crucial to their success. In our study conditions, the Nitro radish cultivar has the highest overall mean germination percentage and proved to be successful across a range of air temperatures and water treatment combinations. The findings of this study have potential value in providing estimated germination rates of these cultivars across a range of environmental conditions, including sub-optimal air temperatures and water levels.
Marcus David Jansen
Jansen, Marcus David, "An evaluation of tillage radish (Raphanus sativus L.) to alleviate post-construction soil compaction and germination potential under varying environmental conditions" (2021). Graduate Theses and Dissertations. 18517.