Since nitrogen is so mobile,soils often test deficient. For an organic source, try alfalfa meal. It has P&K as well but in relatively low levels so less of a concern and it is less of an animal attractant than blood meal (which can burn roots) as well. You will have to wait until later in the season to apply. Organic ferts require active soil organisms to convert them into a plant-usable form and the soil needs to warm up before the little guys start becoming active.

What GG said. You can do blood meal, but don't sweat the N deficiency too much, esp if you took samples near the end of the growing season.

Dan

why do you think your trees need food???

how old are these trees..

how big

what signs on the trees themselves... indicate any kind of problem???

ken

Not organic, but ammonium nitrate(NH4NO3) supplies only N, and no P or K. Should be readily available at your local farm supply, feed & seed type store.

I use it for my nut trees, which are heavy N feeders once they come into production, but for almost nothing else. Guess if I were into the 'lawn' thing, I'd probably use it for fall fertilization. But, by & large, I don't see much need to fertilize ornamental trees in the landscape, and rarely find any need to do much in the way of 'feeding' for established fruit trees.

Try Milorganite or a product like it....this is what you apply when you don't need P and K.

Here is a link that might be useful: Milorganite

When was this soil test done? Nitrogen availability can be affected by cold (or very dry or flooded)soil. Even under ideal conditions I'd hesitate to act on a test showing nitrogen is lacking unless there were some other signs of stress.

tj

Here is a link that might be useful: Search for

In rainy areas N is often the only one that needs to be supplemented. In extra rainy outer coastal areas P may also be low. But P is often over-applied in home gardens, can build up to produce a toxicity to plants. And since it does not leach much, over-fertilized soil pretty much has to be dug up and replaced to get rid of the buildup.

Keyrimeny, what happened to my link name? That should read Search for cold

tj

I often use soybean meal which is 7-1-1, mostly nitrogen but the idea behind organic fertilizer is to improve the soil via biological activities which in turn will help improve tree's health. You are basically feeding soil microbes which would in turn grow and expand, improving soil. Entirely different concept from synthetic fertilizer. If your soil is in bad shape biologically, you may not see immediate improvement in plant's growth. I think it's important to do fall and spring organic fertilizer to keep soil biology working at optimal level to keep plants healthy at your place surrounded by streets and houses where soil was severely razed and compacted by builders. Very little nutrient cycling (big emphasis on that) as opposed to acres of lot like Ken's which he doesn't seem to understand the concept of soil food web because every single time, he says there's no need for it at all without really looking at the whole picture. Oh yeah, not to mention, applying cheap generic animal feed is a whole lot cheaper and easier than compost.

Here is a link that might be useful: soil food web

Let us step back after Lou's good advice and restate that N may or may not be deficient depending upon when and where the sample was taken. In addition, trees in turf are rarely N deficient. So there needs to be lots more context before anyone takes action, as we are...deficient...in info here. IMHO trees in urban/suburban areas rarely need N.

Dan

A lot of nitrogen promotes a lot of weak new growth. The bugs love it, especially aphids on some trees. It can result in damage where it might not otherwise occur.
I never use fertilizer on my garden. In some pots, yes, but never on the garden. I concentrate on soil health instead.

Is this for your trees or lawn? For some reason I thought lawn at first but since this is in a trees forum I assume your trees, but I never heard of someone applying nitrogen to their trees.

I'm sure you have plenty of NFTs (nitrogoen fixing trees) and shouldn't be worried about it.

I respectfully disagree with the naysayers on the forum that say NEVER fertilize trees. Scientific studies show that adding Nitrogen is beneficial to lawn trees that don't receive natural N from leaf/twig litter as forest trees do.

The International Society of Arboriculture sells a great book on the subject: Tree and Shrub Fertilization: Proceedings from an International Conference on Tree and Shrub Fertilization. It contains several studies concerning methods, long term growth and health, etc. A lot of people believe adding N increases pest problems. There is a specific paper on the subject that reveals the exact opposite.

The studies all show the same thing - routine N surface applications in either the spring or late fall are very beneficial to trees. Slow release N is the safest to use but is more expensive. The other nutrients (primarily P and K) can be determined from a soil test. Soil tests for N are a snapshot in time and cannot be relied on routinely to determine N needs.

If the trees are in a lawn setting and haven't been planted in the last year, add N for a healthy tree.

I think there are too many factors involved to make broad generalizations in either direction. Fertilizing trees may very well be appropriate under some circumstances and under other conditions, quite unnecessary. A great deal depends on the tree in question, its age and its growing conditions - not all species require nitrogen at the same levels; some are more able to obtain adequate nitrogen from atmospheric sources; older, well-established trees have reduced nitrogen requirements and soil conditions and mulching practices may preclude the need to supplement with ANY applied nutrients.

If your soil has average pH (6-7) and an organic matter content of 4% or higher, that soil is able to contribute the equivalent of 1-2 pounds of nitrogen per 1000sf per year. That is sufficient to support the healthy growth of all woody plants. And if your trees are planted in the lawn or adjacent to it and your lawn is fertilized regularly, no other fertilizer for the tree is needed.

Excessive amounts of nitrogen can have detrimental impacts on tree health. It can negatively impact flowering and fruiting. Excess nitrogen increases water stress and reduces drought tolerance. It impacts the root system by delaying or reducing the carbon allocation and decreases root reactivity to damage or stress, including cold tolerance. And it can cause extension or elongation of nodes, resulting in a leggy, lanky growth habit.

And I'd not put too much stock in a single paper that disputes a correlation between excess nitrogen and pest problems. The succulent new growth that results from excessive or fast-acting nitrogen applications IS attractive to certain insects and the correlation is well studied and thoroughly documented.

As with any other type of fertilizer application, it is important to know your plant and your soil before applying. Look for signs that the plant is struggling or displaying nutrient deficiencies. Have your soil tested by a professional lab that measures both nitrogen and organic matter levels (home test kits don't cut it). And apply only as directed by the test. And avoid fertilizing routinely like most fertilizer manufacturers would like you to believe you need to do - trees are not lawns and if warranted, fertilizing every 3-5 years is typically all that is necessary to maintain their health and well-being.

I've found many references that nitrogen should only be applied if directed by a well qualified arborist.

Otherwise there is no need to apply nitrogen willingly or if a soil test shows low nitrogen (wheather by a lab or not) as there are too many variables that effect that level.

johnstaci, policy and practices are not changed based on one paper.

The general urban forest standards are still set by Miller and wrt this topic Harris, who wrote many of the questions on the ISA-Western chapter test and by Struve, whose work is cited by many municipalities in justifying their outlays. Here is what Struve says: Although the logic behind early spring N fertilizer application is faulty for trees under clean cultivation, it may be an environmentally responsible practice for fertilizing trees growing in sod where grass clippings are not removed.

Recent concern about the effects of high N applications on plant health and environmental quality have caused a reevaluation of fertilizer practices (Miller 1998, 2000). High N applications reduce the concentration of defensive compounds, increasing the trees susceptibility to certain pests (Herms and Mattson 1992). However, high fertility increases growth rate and often results in nutrient loading. Nutrient loading is defined as an increase in the eedlingÂs nutrient concentration without a significant increase in dry weight (Malik and Timmer 1995). Nutrient-loading conifer seedlings increased planting stock quality; they established more rapidly on stressful sites than non-nutrient loaded seedlings (Malik and Timmer 1995, 1998; Paquin et al., 2000; Imo and Timmer 2001). Lower concentrations of defensive compounds caused by high fertility levels during production can be compensated for by pesticide applications, which act as surrogates for naturally produced defensive compounds. However, the use of pesticides in landscape sites is not as easily done as in the production environment. The benefits of nutrient-load nursery stock planted in stressful urban sites needs to be tested.

The reason for fertilization is to supply nutrients determined to be deficient to achieve a clearly defined objective (ANSI 1998). The objectives include correcting a visible nutrient deficiency; eliminating a deficiency not readily visible that was detected through soil or tissue analysis; increasing plant growth, flowering, or fruiting; or to increase plant vitality (Smiley et al. 2002). Further, the fertilizer should be applied in the manner most beneficial to the plant (ANSI 1998). Before a mineral nutrition program is prescribed, the objective of the mineral nutrition program must be stated. If the goal is to maximize growth in the nursery, then soil fertility should be maintained in the high range (Darrah 2000; Smiley et al. 2002). However, if maintenance of an acceptable aesthetic level is the goal, as in a landscape situation, then lower soil fertility levels are appropriate. In addition to meeting the aesthetic goal, low to moderate soil fertility would likely maintain natural plant defense mechanisms. The difficulty in meeting a fertilizer objective is that soil test calibrations [how much fertilizer needs to applied to effect
the desired response (adjusted for soil type, species, and geographic region)] for the different management objectives (maintain vigor of old trees, maximize growth of recently established plants, or achieve rapid growth during production) are lacking for most woody ornamental species (Darrah 2000). Current N application standards are 1.0 to 1.5 kg/100 m2 (2 to 3 lb/ 1,000 ft2) to maintain mature tree vitality and 1.0 to 2.0 kg/100 m2 (2 to 4 lb/1,000 ft2) to increase growth of established small trees and higher levels (Smiley et al. 2002). [footnotes omitted, emphases added]

Humans already fix as much N in a year as nature fixes. Urban eutrophication into receiving waters makes many urban streams the most polluted waterways in the country. Willy-nilly stating that one should apply N for a healthy tree is not only against proper arboricultural practices, it is irresponsible to the biosphere at large.

Dan