Last summer, we finally pulled the trigger on buying a house after many years renting, and in anticipation of eventually cramming as many fruit trees as possible onto our ~6600 sq ft lot, I decided to order a couple soil tests (one for the front yard, the highest ground, and one for the back yard, the lowest ground).
I’ve never done a soil test before, just relied on a simple pH meter and hoped my compost and occasional fertilizer applications were ok. So, I’m not really sure how to read this, and what kind of actions to take to prepare holes for trees (most notably cold-hardy avocados, but also planning a variety of more zone-appropriate things).
More compost and organic matter (i would have thought you would be higher in Seattle) definitely some nitrogen and potassium as well as a bit of dolomite lime and maybe some gypsum or soil sulfur for sure. I would also do a application of rock dust like azomite, greensand, glacial rock, trace mineral blend etc…
Low pH 5.7 and low nitrogen. Would benefit from adding lime. Waste of time to plant avocado in Seattle. Not hot enough in summer too cold in winter. Duration of heat is way low. It is hot in avocado growing places 9-12 months of year. You have at most 3 months of not hot enough weather. 50s lows in summer not conducive to semi-tropicals. Do you have hardpan soil which is like concrete with small rocks or topsoil?
Definitely planning to keep things as organic as possible, but willing to spray for fungal issues if needed. Thanks for the suggestions!
Thanks for the reply!
I’m definitely aware that Seattle isn’t an ideal climate for avocados. However, many non-commercial varieties of Mexican-race avocados do well in the Mexican highlands and areas along the Oregon/northern CA coast that have similar summer heat to Seattle. I’m putting my mother trees in a greenhouse and planning to cross-breed all the hardiest varieties available in search of seedlings that can survive here. I’m not expecting high or even moderate success rates, and would accept total failure, so it’s more like a mini-experimental research station. The coldest temperature in the 4 years I’ve lived here was ~23° and I’ve never seen the ground freeze solid, so I’m cautiously optimistic that Seattle is warming quickly enough compared to many other locations that over the coming decades it will slowly become more conducive to some of this stuff. Here’s my thread for the avocado stuff:
As for the soil, there’s a layer of true topsoil but below that it’s medium-hard hardpan (more like slightly compressed clay/sand mixture that is easily broken with a shovel) ~2 feet below the surface in the back yard and ~3-4 feet below the surface in the front yard. There’s a layer of pure glacial clay about 5-6 ft below ground level in the back yard, but I haven’t dug that deep in the front yet to see what it’s like. The front yard is about 6 or 7 feet higher than the back yard, so not sure if that’s just thicker topsoil or if the clay also slopes up.
pH is too low for apples and pears and most fruit trees to do well. You have pretty decent organic matter content, anything above 4% is usually good, obviously can always make it better over time with organic mulch. Definitely going to need a little Nitrogen. Nitrogen leaches easily out of soil so no sense in amending it to your soil prior to planting, add it once you have growing plants.
Your nitrogen is low. However this is easaly fixed with fertiliser (organic dung, or even artificial fertiliser). Nitrogen is verry soil mobile. it esily moves trough the soil with water. This leads to runof. This is the reason why you usually see beter result giving a bit of nitrogen every year (or more times a year) than giving a lot 1 year, and nothing the next. The good news however is, since nitrogen is so mobile. just laying some nitrogen source on top of the soil is enough and it will “mix” naturally.
I would use a “organic” (organic as in carbon source animal dung not artificial fertiliser) Since this will also slowly release nitrogen witch means longer effect and less runoff.
Your P is high (phosphate phosphorus) this usually is not a problem. Would just be a waste of money to increase it though. So basicly do nothing about this.
Your potassium could be a bit higher. But is not worrysome low to me. Potasium is reasonaly soil mobile. You will see quickest results if you mix it with the soil. But it will also slowly move down into the soil with water/rain. Some plants like high potasium (like tubers/garlic) It might be worth it to give those plants some extra on the spot/bed where you plant those.
Since your PH is reasonaly low you could increase it slightly. If your increasing it with lime. take the dolomitic lime (contains both calcium and magnesium) This wil also increase the amount of magnesium in your soil. However, keep in mind that increasing your PH is cheap and easy. Decreasing it after you increased it to much. Is really hard and expensive or just not possible. Id always be cautious with lime. It takes a while to take effect. So either be conservative with dose and wait half a year or longer and go again. Or search for more information. (there are calculators online. Witch take your CEC= Cation Exchange Capacity= Basicly how much of a spongue your soil is for fertiliser but also calcium and PH buffering) And take the acid neutralising effect of your choosen lime. And can give you a more accurate advise on dose. Still better to spread the dose in 2 or 4 times over 1 to 2 years, than all at once.
Your sulfur is low. I am not sure how inportant this is. I however know that most animal dung fertiliser is higher in sulfur. So using that as your nitrogen source would also help your lower sulfur.
Your sodium is low. Great you want low sodium. Only exception might be salt loving plants (i think beets do slightly better with more sodium. but imo not worth risking ruining your soil with to much sodium)
Long story short. Some organic (organic as in carbon source not artifical) Dung fertiliser wil increase your organic matter + nitrogen + Potasium + sulfur. You can work this into the soil. But also leave it as “mulch” and let the soil life/worms work it down into the soil.
If your going to lime. Use dolomitic lime and be carful to not overdose. You can search for a calculator that takes your CEC of your soil and the acid nuetralising effect of the lime your gonna use into account for a better dose advise.
I took to long writing my post, and you beat me to it.
I however want to add, that if your nitrogen source is not artificial fertiliser but more organic matter, the leeching will be slower and you can apply it a bit more in advance. It is still best though to wait until it’s needed and loose less to leeching.
Any thoughts on municipal compost as a source of nitrogen & organic matter? Seattle has mandatory household composting and you can get the product of that basically for free. The one time I got some it had bits of plastic in it and smelled like it wasn’t done decomposing, so that turned me off to the idea, but it’s hard to beat the price.
Depends on the makeup of the compost. If grass clippings is part of it there may be insecticides and weed killer chemicals in it. If sludge is part of it you can get unknown chemicals. Some municipalities only use leaves and wood chips that I think are safer.
Here near Houston we have the hot weather for growing avocados. However they require perfect drainage. Two days of soggy roots killed my friend’s grafted “cold hardy” avo. Same friend has a 50+ foot tall seedling Mexican, seedling because the graft froze. He grew lots of fruit for the squirrels with fruit not as good quality as Haas. However our recent 10F has his tree shedding all it’s leaves. Doubt it will survive. So 99% of growers fail, mostly due to freezing weather of any kind even with “cold hardy” avocados. A friend had a 34+ foot tall Day avocado. Then we had an ill timed freeze and it froze to the ground. His rootstock stump was attempting to regrow but likely was killed by our recent 10F with 4 days of freezing weather. We don’t have 9 months of daily rain here like you do in Seattle. I know the weather you have, I was born in Seattle and lived there for 14 years with 4 years at UW. But good luck anyway. I wouldn’t waste money on grafted trees. Seedlings can take 10+ years to flower but likely won’t survive that long in Seattle. And you need a type A as well as a type B flowing tree. Good luck anyway but I think you may have a better chance to win the lottery!
Avocados grow near San Diego. They do have hot weather in the summer but seldom get a freeze. They grow in Miami as well but they never get a freeze and grow the Guatemalan avocados. Ditto for “cold hardy” citrus in Seattle. ColdHardyCitrus - mrtexascitrus
Beware of “cold hardy” avocados from Texas near San Antonio. If they survive without freezing the fruit tastes like grass. I’d rather have a Haas myself. Don’t know of a single person in Houston that has a bearing avocado tree with fruit as good as grocery store fruit.
Oh BTW, most avocados propagated at least in Florida that arrive here in Texas, have rootstock that is not cold hardy. So your “cold hardy” graft may live but the rootstock may die. Not really much of a market for avocado tree outside of Southern California so can’t comment on rootstock of trees propagated in Cali but likely rootstock not selected for cold hardiness as they don’t get freezes in SoCal.
The varieties I’m focusing on have done well in northern CA with regular winter freezes, but you’re very correct that the rain/wetness is probably the worst part of our climate for avocados. The slope of my yard and sandy topsoil will help some, but probably not enough. We shall see! At the very least, I’ll have a greenhouse full of avocados…
The cold hardy varieties from northern CA that I’ve tasted were superior to Hass in my opinion, higher oil content and richer flavor. A little smaller, with much thinner skin, but tasty. I haven’t yet tried many of the other varieties I’m growing, but hopefully some of the larger ones will produce in the greenhouse this year or next.
Yup, the FL and Texas nurseries mostly use Lula rootstock, CA mostly use Bacon or occasionally Duke-7, which are slightly cold tolerant compared to Lula, but not great. That’s a big part of why I’m keeping the grafted varieties in the greenhouse and planning to plant out only seedlings after they are ~ 2 years old. I am also trying both air-layering and rooting of cuttings, after reading old research papers that said Mexican race avocados root much more easily than Guatemalan or WI.
I always like talking to an expert face-to-face about gardening advice, and really like the help I have received from the local “County Extension Office.” I see that the Kings County Washington office is closed, however, due to the Wuhan China virus. They DO have a part-time staff, I see, that you can email to ask questions about your soil test results…and also get advice (free) for the practical methods of amending your soil, fertilizing, & etc., and help with doing the math and calculations for chemicals and such. Here’s the link: King County | Washington State University
Normally there is also a lot of other information that can be found by following the links on the County Extension website(s).
And I might also add, if there’s a will there’s a way! If fruit trees are want you want and the soil is not desirable, as long as the weather is acceptable, the soil can be amended to grow your trees, I should think.
Some neighbors grow some great looking grapes, but I don’t have any experience with them and haven’t looked into varieties at all. I could probably ask the neighbors what they are growing and if they know what rootstock it’s on. Thanks for the suggestion!
Yuck, that’s all you have for a CEC??? And I thought my soil was bad! After reading about sandy soils being around a 5, but that clay soils could be that low too if you had the wrong kind of clay, I realized that somewhere there’d be something on the CEC for our kind of clay. I called the county agent and asked what the CEC ran for Christian Silt loam and they finally found it. A 12, which is not bad. Someone asked Neal Kinsey would would be his ideal soil, and he said a light sandy loam about CEC 12. Alas, ours is a lot harder to work with, but if I add nutrients, they stay put. Lucky your organic matter is reasonably high.
From what i understood/ gues. Only the topsoil (low in clay) has been tested. I suspect the deeper semi hardpan with the clay sand mix is not seen on the soil test. Is this correct @swincher ?
Or did you dig deep for a mixed soil sample?
A higher CEC is usualy “better”. Although a low CEC isen’t the end of the world. Just means you have to spread out your fertilisation over time. Or depend more on slow releasing ferts.
A cover crop of the legume family might also be worth considering. Like clover. There is a topic about that, and im gonna try a few types of clover this year.
read about it here
4.2% OM is a reasonable and sustainable amount so I wonder why there is focus on this in responses. You aren’t trying to grow corn or a crop that benefits from rich soil if your concern is fruit trees. Some of the best quality fruit I harvest is from some of the weakest soil- sandbox material.
However, I live where it rains during the growing season and a high amount of organic matter may water down brix by providing too much available water during the last month or so of ripening.
The main issue you want to straighten out is pH before planting, if your soil has good drainage and is reasonably deep.
You might want to submit a soil test through your cooperative extension which probably will include specific instructions on the amendments you need for the crops you want to grow. A service that just gives numbers is inadequate for amateurs and even though I manage orchards for a living, I haven’t developed the knowledge to look at a lot of these numbers and automatically know what they mean.
That is because for most of those numbers there isn’t a lot of significance- nutritional deficiencies in fruit trees are pretty rare in soils around here- at least those that create obvious crop issues. All over the country, besides water, oxygen (and sun) the only nutrient that will create a noticeable response in a tree is nitrogen. The nitrogen in organic matter is released at the wrong time for mature fruit trees- when the soil is warm and moist in early to mid-summer- N improves crop load and fruit quality only in spring. Summer release encourages vegetative growth at the expense of fruit quality. However, this isn’t such a problem in parts of the country that don’t get significant rain in the summer because growth can be regulated at the spigot.