Bulb Soil Mixes and Fertility

[illahe]

Hi All,

I've been enjoying the discussion on the forum on Fertilization of bulbs in cool soils on the thread and forum. I thought I might put this little ditty up up on Soil Fertility as it might augment the discussion.

For years for my commercial bulb production mix I have used a mix of:
1 part Pumice
1 part composted cow manure (a local product sold in bulk called Moo Doo, from local dairy use)

I usually get these in separate parts and mix them together blending a bit more pumice for very dry loving species and a bit more composted cow manure for anything that wants to hold a bit more moisture. Nothing scientific about the additions, just based on some years of growing different species and seeing the response.

With some increasingly hot and dry summer weather, as well as a longer dry spell between rainfall here in the Northwest, a few years ago I started to add in a sandy loam topsoil to hold a bit more moisture (mostly for the dry season) so the mix is now generally:

1 part Pumice
1 part Composted Cow Manure (CCM)
1 part sandy loam topsoil

I have liked the results of this mix and I apply the same logic above with blending a bit more pumice for some things and a bit more CCM and sandy loam topsoil for a bit better moisture retention when necessary.

A few years ago I was working a day job at our County level Soil and Water Conservation District and was advising farmers on the importance of soil testing to better manage fertilizer applications to avoid excess nitrogen runoff into local streams. It occurred to me that I hadn't had my revised mix tested and had been following my general fertilizer regime of using a bloom based Cal/Mag water soluble fertilizer. So I actually bucked the old adage "Do as I say not as I do" and had my bulb mix tested.

Here are the results:

[url="https://www.pacificbulbsociety.org/pbsforum/index.php?action=dlattach;attach=3096;type=preview;file"]bulb mix soil test.pdf[/url]

I have been having good results with this mix and the test results were a bit eye opening when I actually had it looked at by a lab. I had always assumed I had a pretty high nitrogen source with the composted cow manure and that wasn't actually the case. The pH is maybe a bit high, but honestly the Calcium level was great and most of the macro and minors are in good numbers for most bulbs. I've always thought the sodium level was going to be a problem, but I had already been using this mix for several growing seasons by the time I decided to have it tested and have never seen any issues with salt toxicity.

I talked a bit about the fertilizer regime I now use on the email thread, but I think this is a good follow up to that discussion that it can be really beneficial to have your soil tested so you know what base levels you are starting with. The last few years the ag community has seen fertilizer prices double and even triple, so it can be quite beneficial to have your soil mix tested and tweak the fertilizer usage from there to save some money. I had my garden bed soils tested at the same time as the bulb mix and I think I paid less than $100 for both samples. You can often shop around and find cheaper options if you have multiple soil labs in your area. Collecting and sending a sample in is easy and they will give you instructions on exactly what to do.

Hopefully this may be helpful to someone,

All the best,

Mark Akimoff

[Rick R.]

Thanks, Mark.  The Link to your lab test brings a question/comment:  correct me if I am wrong, but with nutrients like iron, copper and manganese where your test shows low presence, wouldn't the high pH effect an even lower availability?  Wondering if you may have unknowingly experienced any deficiencies, or perhaps the high pH doesn't bring the deficiency low enough to show symptoms.

[petershaw]

Hi Mark,

We have used that lab for years and the price is quite fair.

IN my opinion, looking at the results show the impact of the addition cow manure.

there are several things I would be concerned with, the pH, EC and Na levels are very high while the N is quite low. Cow manure is usually very high in salts as seen by these elevated levels and the mineralization rate of N is slow over time.

My biggest complaint with animal based compost is the high levels of P compared to the other primary nutrients.

Anyway, just my opinion, as I have told my students over 30 years, if it works for you, fantastic!

[illahe]

HI Peter and Rick,

Thanks for the response this is exactly the discussion I was hoping to have since it makes me think deeper about the way I'm doing things and incorporating others knowledge into the equation always leads to better results.

In response to Rick's question about pH, absolutely I do believe the pH effects the availability of the listed micro nutrients, the chart most gardeners are familiar with illustrates that:


 I do fertilize with a liquid feed regularly during the growing season, so I'm supplying the necessary micronutrients regardless of the pH. Lately I've been using a Peters Dark weather 15-0-15 Ca/Mg with micros. This has been the best fertilizer I have found for winter growing bulbs. Later in the season when things warm I switch to a bloom based fertilizer, honestly I mostly use whatever is on sale at the time, but do often use peters 15-5-15 Ca/Mg as well, usually starting in April and going up until the bulbs are starting to senesce.

Peter, I do agree the Salt level is high and I probably should be more concerned about it, but I haven't seen any issues with it and my guess is that it's related to the use of mychorrizae in the soil which I add as a granular to bulb batches and have also been experimenting with a Water soluble VAM product. Check out this interesting article:
VAM and Salt Tolerance in Plants

Honestly the reason I use the cow manure is out of pure necessity. I don't trust our local yard debris compost, I have had so many issues with it containing herbicide residues that I don't risk using it in soil mixes anymore. I've tried several different suppliers over the years here and only one can regularly pass the cucumber assay test but it's far to coarse to use for bulbs and would require so much screening (something I just don't have time for). The Sandy Loam topsoil is an always changing product, but the composted cow manure has a pretty good consistency to it so that I can count on some level of standard drainage/soil moisture holding capacity.

When I first started into bulb growing under the tutelage of Jane McGary as a mentor, I watched her screen Alder leaf mould from her woodland in Estacada as an addition to her soil mix. I'm sure she has written about that over the years and you could find it in the archives here. I used to go and screen oak leaf mould, as that is what I had access to,  by using a garbage can with a 1/4 hardware cloth frame over it and shred it until it was a pretty fine product. That gave me some of the best bulbs I ever grew. Unfortunately as my time is so limited and the nursery expanded It's simply not economical to go and shred oak leaf mould.

The soil mix I'm currently using works for a wide range of species, is fairly cheap and available. As a grower I'm totally open to suggestions and would love to hear more about what works for others as well!

Thanks,

Mark