Effects of increased autumn temperatures and sub-acute levels of ammonia on post-winter development of four cultivars of winter oilseed rape (<em>Brassica napus</em> L.)
AbstractEarly planting dates, warm autumns and increased N mineralisation rates may advance the growth of winter crops and also a high supply of nitrogen poses risks of excess biomass accumulation before the winter leading to reduced frost hardiness and excessive leaf loss. Although the number of frost days is currently declining in temperate Europe, events of frost may still create damage in the future in winter crops that have accumulated too much biomass in the preceding autumn.
Here we report on a study in which the responses of four cultivars of winter oilseed rape (OSR) to elevated autumn temperatures and subacute levels of ammonia (NH3) were compared. It has been suggested that high concentrations of the gas, e.g. in livestock intensive regions may both act as an airborne fertiliser and reduce the frost hardiness of plants. Advancing treatments were imposed for 88 days in the autumn and consisted of pot grown plants kept in greenhouses without (ELVT) and with elevated concentrations of ammonia (ELVT+A; 195 μg m-3 NH3). Reference plants (AMB) were raised outdoors, where temperatures were 1.4°C lower than in the greenhouses.
After the treatments plants were all overwintered outside to study whether the pre-winter growth advancement was still discernible in the following spring. Shed leaves were collected weekly to follow how much shoot biomass was lost during and after the winter. Cultivars responded differently to warming and exposure to ammonia. Up to the winter shoot biomass was strongly increased by the advancing treatments. However, fi nal shoot mass in the following summer did not differ between cultivars and was unaffected by the higher temperatures in the preceding autumn. Nevertheless, significantly more biomass was observed in ammonia fumigated plants. Higher autumn temperatures increased leaf shedding and advanced fl owering and senescence in the next spring so that plants showed a signifi cantly reduced seed mass, harvest index and oil yield at the fi nal harvest. Obviously, the growth advancement in the preceding autumn by elevated temperatures negatively affected the availability of resources in the following spring. In contrast, plants that were grown at both elevated ammonia and temperature in the autumn showed a delayed fl owering, higher shoot and seed mass, increased harvest index and oil yield. We conclude that growth advancement by elevated autumn temperatures without the re-supply of nutrients increases leaf shedding during winter. Nevertheless, the loss of resources in winter for re-growth in spring will certainly be of minor importance for yield formation as compared to the frost damage resulting from late spring frosts.
From Volume 92 (2019) on, the content of the journal is licensed under the Creative Commons Attribution 4.0 License. Any user is free to share and adapt (remix, transform, build upon) the content as long as the original publication is attributed (authors, title, year, journal, issue, pages) and any changes are labelled.
The copyright of the published work remains with the authors. If you want to use published content beyond what the CC-BY license permits, please contact the corresponding author, whose contact information can be found on the last page of the respective article. In case you want to reproduce content from older issues (before CC BY applied), please contact the corresponding author to ask for permission.