Two Feeding Questions

[Oldbear]

Is there any methods or tools to measure the nutrient levels that are in soil?

Does anyone know how long a plant takes to utilize all the 'food' in a cuft of soil?

 

[KingJoe83]

Is there any methods or tools to measure the nutrient levels that are in soil?

Does anyone know how long a plant takes to utilize all the 'food' in a cuft of soil?

Ppm meter?

 

[Scientific]

Ppm meter?

A PPM meter is one great tool and a pH pen is another.

Google "soil test kit." I'm thinking in particular of the Rapitest Soil Test Kit that sells for about $15 at garden stores and has separate tests for nitrogen, phosphorous, potassium, and pH.

I have never used one before, but it looks like you add some soil to a little clear plastic container, add some drops or powder, and you get a color for a result. I have a new vegetable garden patch that I'm going to start working in the spring and I will definitely be using one of those kits then.

 

[Scientific]

Does anyone know how long a plant takes to utilize all the 'food' in a cuft of soil?

How rich is the soil to begin with? How hungry is the plant that's growing on it? Too many unknowns in most cases to say, but of course every crop is going to deplete the soil that much more.

 

[Oldbear]

Ppm meter?

Ill research this. Would the same tool measure in water dissolved solids by chance?

 

[KingJoe83]

Ill research this. Would the same tool measure in water dissolved solids by chance?

Yup when I run my tap water through coco to flush it it reads 1200 ppm. My tap is only 150 ish. So this tells me there is a lot of nutrients salts etc in coco . Also tap water calling your township to see if they have water specs is good to . Not necessary but a thought ,

 

[Oldbear]

A PPM meter is one great tool and a pH pen is another.

Google "soil test kit." I'm thinking in particular of the Rapitest Soil Test Kit that sells for about $15 at garden stores and has separate tests for nitrogen, phosphorous, potassium, and pH.

I have never used one before, but it looks like you add some soil to a little clear plastic container, add some drops or powder, and you get a color for a result. I have a new vegetable garden patch that I'm going to start working in the spring and I will definitely be using one of those kits then.

Ill research soil test kits to see whats up with those.

My old brain is like a sponge soaking up things. Well maybe a leaky sponge now.

Anyway now I'm wondering if there is a chart somewhere that shows a 'best' ppm range for nutrients in the soil for happy plants. Ill go hunting for that too.

Sounds like one could do regular tests to determine nutrient depletion rates, and also when to

 

[KingJoe83]

here is starting point I think for most photos .not autos

 

[Scientific]

Anyway now I'm wondering if there is a chart somewhere that shows a 'best' ppm range for nutrients in the soil for happy plants. Ill go hunting for that too.

I'm pretty sure the soil test kit instructions would have tips on that. That and a gardening website...

(I'm reminded of my college friend Jerry the agronomy major. He was growing corn in "defined media"--pure sand to which he would add exact amounts of particular nutrients to see how the plants responded. I would love to have access to that plant physiology lab and all those fertilizer components!)

 

[Oldbear]

Ive had some google time today.

There are lots of inexpensive soil test kits available. They look easy to use.

I don't see a lot of soil testing actions in grow journals. Why would people guess at when their plants need (or don't need) to be fed?

 

[Scientific]

Why would people guess at when their plants need (or don't need) to be fed?

That's an interesting question. I guess it's because you can just mix up some fertilizer and pour it on and be reasonably sure that the plant will get what it needs without having to do a lot of extra work. But it would be kind of interesting to track levels during the grow.

 

[TheFertilizer]

Well from what I've read, most people don't really trust those cheap store-bought soil fertility test kits. A lot of the time they don't test individual elements, or if they do, it's often actually a measure of electrical resistance or some other form of gross estimate rather than an actual measure. For an actual test, there are laboratory services, a lot of states even have a county extension program that offers soil testing for pretty cheap, like $10 or less. You just send a sample to a lab and they analyze, and you can get a number of different tests done with a lot more accuracy.

But yeah I think for the most part the general routine of feeding bottled nutrients is what people tend to do, or even when going organic, they'll just whip up a "super soil" that has everything the plant could want, so actually measuring the soil is more practical if you're trying to use outdoor soil as-is, or if you're trying to create your own soil mix recipe, if you think there's a specific problem, etc.

I've got a sample I sent off last week but it will probably be a week or more before I get results back. There's some soil tests results in the Organic Soil sections of the forums but yeah most people don't really bother

I think people get the wrong idea about run-off testing. You have to keep track of it to have your own data to compare to. So if for example, you see the ppm level of your run-off spike, you'll know that your soil is loaded with salts and needs flushing. However, if you haven't kept track of it with your own data, then you'll have no way of knowing if the ppm level of the run-off is abnormal but to guess.

 

[Scientific]

Well from what I've read, most people don't really trust those cheap store-bought soil fertility test kits. A lot of the time they don't test individual elements, or if they do, it's often actually a measure of electrical resistance or some other form of gross estimate rather than an actual measure.

The kit I mentioned has four tests--pH, N, P, and K--and they're all color-based. I used to test nitrate in my aquarium and I'm sure it must be the same test in the soil kit. The more nitrate there is, the purpler it gets, and you read the nitrate level of a color depth chart. Really simple, easy, and accurate. I don't now about the P or the K. I do know that lots of times chemical tests require careful execution and knowledgeable interpretation... Anyway, it will be fun to try a kit in the spring. I wonder if I could use it to test the N, P, and K in my hydroponic reservoir?

 

[TheFertilizer]

The kit I mentioned has four tests--pH, N, P, and K--and they're all color-based. I used to test nitrate in my aquarium and I'm sure it must be the same test in the soil kit. The more nitrate there is, the purpler it gets, and you read the nitrate level of a color depth chart. Really simple, easy, and accurate. I don't now about the P or the K. I do know that lots of times chemical tests require careful execution and knowledgeable interpretation... Anyway, it will be fun to try a kit in the spring. I wonder if I could use it to test the N, P, and K in my hydroponic reservoir?

Yeah I think they have their merit, but the downside is that they're probably going along a generalized scale of "optimum" or "too much" or a generalization like that? With a laboratory soil test you'll be able to get the exact percentage of such elements, including to micro-nutrients, as well as cation exchange capacity, pH, etc. Given that lab tests are almost just as cheap if done through a county extension service, it's hard to recommend those kits over a lab test. On the other hand, they're probably a lot more convenient to get fast and easy results immediately, that way you're not sitting here twiddling your thumbs waiting for results like me.

But I never had luck with the meter-style ones from RapidTest. I have some soil I mixed up that is very, very rich and it still reads as "too little" on the fertility meter. I think the chemical "reagent" tests like the one you're describing are probably a little more accurate since they're actually reacting with the chemicals to make that color change. How do they work as far as quantifying the results, is the intensity of the color an indication of nutrient amount?

 

[Scientific]

Oh, if you're talking about those horrible all-in-one meters that they sell at the garden store, those are best used for ballast.
I meant a pH meter and a PPM (electroconductivity) meter.

I wonder if the county that I live in, at the center of a megalopolis, has an ag extension service. There used to be farms around here 50 years ago, but... worth a look, I guess. Thanks for the suggestion!

<edit> I just went out and looked at the test kit label, and sure enough, the color bars say "Deficient, Adequate, Excess" or words to that effect. Still, they could be useful (and of course the average gardener wouldn't know what to do with a number).