Soil improvement

4 years ago

last modified: 4 years ago

I received soil test results yesterday and the interpretive information and recommendations were not what I hoped for so I am going to see if anyone here has any advice. I am growing roses and perennials elsewhere, but thisnis a new bed area.

My soil is mostly light and sandy with a few arreas that were probably filled with clay at some point. The rose growing areas though are primarily acidic sand (pH of 5.5).

I was surprised to learn that my unamended soil is excessively high in Phosphorus, Potassium, and Magnesium and high in calcium. The soil was only 5.8% organic matter.

Lime was the first and most obvious recommendation along with the recommendation to fertilize with ammonium nitrate or urea rather than a complete fertilizer.

What I was/am most interested though are recommendations on the best types of organic matter to add since I need more organic matter to aid in moisture retention. What ammedments are good for adding Nitrogen and overall organic matter?

Featured Answer

charles kidder

4 years ago

last modified: 4 years ago

High P and K is good news IMO. Good for root development. If you want to add something with a lot of N and not much else, consider any lawn fertilizer that isn't starter fertilizer. probably the cheapest way to add N. But, honestly plants typically get enough N from rain water. Which has usable N dissolved in it. Somehow trees in the wild survive without miracle grow.

As far as organic matter goes, you can use whatever compost is available at local stores. And put on a good layer of shredded hardwood mulch every year. it will decompose over time and add organic matter.

I don't think adding lime is absolutely necessary. Although it won't hurt and will probably help a little. 5.5 is OK for roses. I think optimally roses like a pH closer to 6. You generally need to add copious amounts of lime to make much of a pH difference. And adding lime will add more calcium to the soil.

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Comments (7)

gardengal48 (PNW Z8/9)
4 years ago
I disagree on several points. You do need to raise pH. Below 6.0, potassium, phosphorus and nitrogen ions are bound to the soil and not available for uptake. So even a nutrient rich soil may not support healthy plant growth if the pH is out of whack. You want to shoot for 6.0 to 6.5 and lime is the best way to achieve that quickly.

Any organic matter you can easily and cheaply obtain will work. Yard waste compost is almost ideal but any other compost would be equally effective, including composted manures. They will all provide some N but I'd add alfalfa meal as well. Not only is it a great source of organic N but it contains a natural plant growth hormone that is especially beneficial to rose growing. I wouldn't rely on rain water as a source :-) Much too variable and unlikely to be provided in the quantity that all plants require. N deficiencies are the most common forms of nutrient distress in plants.
Markay MD-Zone 7B thanked gardengal48 (PNW Z8/9)
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Markay MD-Zone 7B
Original Author
4 years ago
I got the second set of results from the sample if amended soil that I grew my roses in last summer and the pH was 6.6.
User
4 years ago
Definitely agree that adding nitrogen is a good idea and that alfalfa is a great way to go. Also, grass clippings and green garden waste(for example, leaves pruned off from a hedge).
toxcrusadr
4 years ago
Funny that the Mg is so high, but I'm from limestone country and we have tons of calcium.

Just make sure you're using regular lime and not dolomitic lime, which is Mg instead of Ca. I thought I read here over the years that Ca should generally be higher than Mg. Not sure if it's that big of a problem though, if gg wasn't bothered.
Markay MD-Zone 7B thanked toxcrusadr
Markay MD-Zone 7B
Original Author
4 years ago
last modified: 4 years ago
These were the results of the sample I submitted from an ammended rose bed. Calcium and pH were both higher.
subk3
4 years ago
For what it's worth I have similar soil results: "Very high P and K, needs N." But my pH is good.

For my roses I incorporate a couple a shovels of horse manure (somewhat but not always competely composted) around the base of each rose when I pruner in early spring and sometimes again later in the growing sesson. Mid/late spring I'll supplement that with either alfalfa pellets (its an animal feed that you can find someplace like Tractor Supply) or Fish Fertilizer an organic 5-1-1. When I'm really feeling industrious I'll make an alfalfa tea and augment it with the Fish Fertilizer. I'm not at all unhappy with my rose growing success on that plan.
Markay MD-Zone 7B thanked subk3