Thanks for pointing us to an interesting site. Not sure your shocking revelation is correct. The info given is the analysis of plant material not the plant requirement - nutrients are absorbed and utilised at different efficiencies from the soil so beware of underfeeding!

Actually, the nutrients plants take up are stored in the plant in some fashion so the tissue analysis is regarded as the most accurate means currently available to determine optimal nutrient levels in the growing medium.

In other words, the best science on the subject tells us that what is inside the plant is the best known method to determine what the plant needs and in what amount. Once a plant takes up a nutrient, it doesn't lose it, it remains in the plant in some form.

Tissue analysis has been combined with soil tests which measure what nutrients are removed from the soil by a crop and for the most part the percentage of nutrients removed from the soil agrees with the percentage of nutrients found within the plant which reinforces the validity of tissue analysis as a means of determining optimal plant nutrition.

Guy, Could you use this information as an argument for the wisdom of utilizing healthy plants as a nutrient source for garden vegetables by way of the compost pile?

Steve

Guy, Could you use this information as an argument for the wisdom of utilizing healthy plants as a nutrient source for garden vegetables by way of the compost pile?

Yes, but probably not in the way one would think. Adding organic matter to the soil with no regard to it's nutrient content is very similar to the use of 10-10-10 synthetic fertilizer. Both are shotgun approaches which do not take the native fertility of the soil into consideration.

Both approaches can result in nutrient run off causing pollution of water.

However, on balance, using an organic 'shotgun' approach is safer for plants as the chemical reactions which easily take place in mineral soils (the dirt) are much less pronounced in highly organic soils. For this reason somewhat elevated nutrient levels in an organic soil won't show problems as quickly as they would in a pure mineral soil (dirt with no organic matter added). Also pH issues are more of a problem in a purely mineral soil than they are in a soil well amended with organic matter. This isn't an endorsement of organics over synthetics, it is simply chemistry and organic soils are more forgiving and less chemically reactive than pure mineral soils are.

Still, I think the information behind the link I provided in the OP is of great use in increasing understanding of what nutrients plants *really* use and in what amounts. For example I was stunned that lettuce uses as much potassium (sometimes 2x as much) as it does nitrogen. Corn uses equal amounts of N and K. I had previously thought these to use more N than anything else and that is not true.

Also of interest is that most plants use more calcium, magnesium and sulfur than they do phosphorous.

To me that is very interesting stuff.

It is "very interesting stuff," Guy.

I'll keep it bookmarked and refer back to the information as thoughts and questions on fertilizing occur to me. One important issue you are raising is the critical need for some nutrients which may even go unidentified on a fertilizer bag.

One point I was trying to make might have to do with raising lettuce, as an example. During the Autumn one can stop at the bin behind the local supermarket and pick up 20 heads of lettuce. This lettuce can be composted and the material incorporated into an area of the Spring garden. All of the nutrients from the 20 heads of lettuce are available - assuming none have been transported out of the compost in some manner.

Yes, there is likely to be an excess of some nutrients but an excess is preferable especially if the gardener intends to grow a crop of lettuce in that soil. Presumably, those nutrient will be sufficient for 20 lettuce plants in this season's garden.

It was just a thought . . . I've carried material in by the "bale" and felt better for having done so. Of course, I may be leaving the ground where that plant material was grown deficient but that is beyond my choice, one way or another. Utilizing compostables, and their nutrients, which would otherwise be lost to food production is something I CAN do, at times.

Doing so takes a little pressure off my shoulders with regards to getting the nutrient balance right for the mixed vegetable crops I'm growing. And, often those plants are growing in the same bed of soil.

Steve

Steve, I think I missed the point you were making in your first post. Your second post I think I understand better.

If I am understanding you correctly you are saying one way to provide all nutrients in an optimal ratio for a plant would be to take a bunch of those plants, compost them and then apply that compost to the soil where you intend to grow the same type of plant.

That makes sense to me. Very creative thinking! The only nutrient I would worry about not being present in ample amount with this process would be nitrogen since it leeches more readily than other nutrients. Still, the idea seems sound to me.

I'm not often accused of having a "sound" thought, Guy.

My idea might have been characterized as a defense of the "Donner Party." We couldn't see allowing those nutrients to be lost because we were hungry!!

I use a conventional approach in the flower garden but only organic practices with the vegetables. The primary thing that bothers me about synthetic fertilizers is not really knowing what is in them.

I don't live far from the eastern Washington farm town whose mayor wrote "Fateful Harvest" about toxins in fertilizers. I'm still not too sure who is regulating the toxins in fertilizers or even requiring public disclosure on some of the ingredients.

Not only am I not sure about what is in the fertilizer that I might not want there but I'm equally unsure about what I would want in the fertilizer that isn't there.

With my ornamental plants I try for a shotgun approach by using at least 2 kinds of fertilizer thru the growing season. If my local "plant food" company didn't put it in their synthetic mix, maybe Miracle Gro has it in those blue crystals.

The University of Florida horticulturalists in your linked article will help me understand what each vegetable crop really needs.

Steve

One big problem you can run into with compost is the source of the material for the compost.

American farmers have long fallen for the chem companies' push of NPK (nitrogen, phosphorus, potassium), and they've totally ignored all the other nutrients: calcium, magnesium, sulfur, silica, sodium, boron, copper, molybdenum, iron, manganese and zinc. Many parts of the country are seriously lacking in these 'less famous' nutrients. And if the soil is lacking them, the crops that are grown on them are lacking them. So, if you use the crops grown on deficient soil, the proper nutrients won't be in the materials that you are using for compost. Thus, the compost will be lacking in those materials. Just because they CAN be a source of certain minerals doesn't mean they ARE a source of those minerals. This also follows with meat production. If the soil doesn't have selenium, the grass doesn't have it, and if the grass doesn't have it, the cows aren't ingesting it, and when they are slaughtered, the meat still doesn't have it. You can't produce elemental nutrients out of air or wishful thinking.

Many nutritionists say that many of our physical health problems stem not only from ingesting and absorbing so many chemicals that didn't exist 100 years ago, but from eating food that is basically devoid of many nutrients.

Blindly adding loads of manure and compost to your soil without soil tests (preferably annually) truly is a 'shotgun approach' as Guy said above.

Sure, add some compost and manure to your soil, it probably does need it. But don't assume that everything your soil needs is in that manure and compost. Get an annual soil test and keep all of them; compare each new one to the ones from previous years. They should show you where the nutritional weak spots are in your soil.

ALL the nutrients are necessary to plant, animal and human health. We can't have just some and expect to be healthy. Find out what your soil needs, and then supply it in the amount required, no more, no less.

Sue

So, if I understand all this correctly, we have health issues due to ingesting things from our soil that was not there 100 year ago - so we should perform tests that were not available 100 years ago when we supposedly ate better, healthier food during our much shorter lifespans.

hm.