Nitrogen Fertilizer and Deer
I was recently told that some plant growers use nitrogen (N) to increase plant growth and marketability. Then, because N increases nutrient content and appeal to deer, the newly planted specimens – even if deer-resistant species – are more likely to be browsed, especially during the first year. Is this information correct? If so, what are the scientific articles that back up this hypothesis? Although I did find an article about N and phosphorus fertilizer (https://www.fs.fed.us/pnw/pubs/pnw_rn368.pdf), it only mentions Douglas fir and was published almost 40 years ago.
Nurseries often fertilize their stock in order to maintain plant health; plants in a container have limited access to nutrients and some nutrients such as Nitrogen can leach out of the soil over time with irrigation and need replacement over time. Plant growth rates can be constrained by a range of other factors, so fertilizer has its limitations.
Deer browse can vary based on time of year and available food sources, as well as the preferences and habits of individual deer. Often they will investigate and sample new plants as a potential new source of food, and given the smaller size of nursery plants compared to more established landscape plants, these suffer proportionately more damage from investigative nibbles.
There have been studies done of fertilizer dosing on the prevalence of insect plant pests, and similarly, the nutritional value of fertilized plants may cause preferential browsing by deer as well. Deer are known to prefer tender, young growth (which fertilization can promote), and young growth may not yet have developed the typical defenses to browsing that mature growth has, such as stiffened spines or distasteful chemicals in their tissues. The best strategy for introducing new plants into a landscape with known deer browse is to either use a physical barrier (netting, typically) until the plants become established and are better able to withstand minor browsing or to use a deterrent such as repellent sprays to discourage tasting and browsing. Certainly, those plants reported to be most unpalatable to deer are the best to try first in the landscape, especially if they are to be eventually unprotected. Some information about dealing with deer browsing and preventing damage can be found on this page: https://extension.umd.edu/hgic/topics/deer.
Miri, thank you for your response. What I really need are scientific articles that say nitrogen fertilizer is linked to higher levels of deer browse. Can you please send me links, or the names, authors and other information on any articles that might exist? Thanks again..
Unfortunately, we do not have research-based information on this topic. You could try searching Google Scholar for research papers, although you may only be able to read the abstract of articles rather than see all of the data.