Rough rule-of-thumb is 2 million lbs of topsoil per acre (top 6 inches). So 10ppm is 20 lbs per acre. You want 80 lbs. Difference of 60 lbs of N.

Excuse me but i cannot understand your answer.

Rule of thumb 2million lbs of topsoil... So is that the weight of the top soil?

So 10ppm is 20lbs/acre..... 10 ppm of what is 20 lbs of what? per acre

If you could clarify i would be grateful

Thank you

We are going to also need your length and width measurements in order to calculate the soil's volume to be amended.

You got your calculation right.

If I had more time I'd show you how to do the calculation on a per 1000 sq. ft. basis so that it would easy for you to adjust the final number based on the size of your area but, gotta go. I'll try and get back to the matter.

Just curious, why do you want to adjust sour soil-N on a PPM basis?

You want to add 60 lbs. of nitrogen per acre. Using the fertilizer you have, you would add 750 lbs. per acre (60/.08). An acre is 43,560 sq. ft. So, for smaller plot you would add roughly 17 lbs. per 1000 sq. ft. or 1.7 lbs. per 100 sq. ft. From there you can calculate the kgs.

Not to toss a fly in the ointment, but nitrogen is subject to leaching, volatilization, etc. The number reported on your soil test is probably not what you have TODAY and is definitely not what you'll have if you're planting in the Spring. Just something to keep in mind.

Excuse me but i cannot understand your answer.

Rule of thumb 2million lbs of topsoil... So is that the weight of the top soil?

So 10ppm is 20lbs/acre..... 10 ppm of what is 20 lbs of what? per acre

If you could clarify i would be grateful

Thank you

If the "parts" are pounds, then 10ppm equals 10 pounds. It is a handy way to easily convert ppm's to weight, you just multiply the ppm by 2 and that is pounds per acre.

OK. Forget about the weight of the soil, the top 6" etc. It's good information for background, but not necessary for your purposes.

To simplify the calculations, we're going to convert to lbs. per acre. Once, we're done you can adapt it to kgs., hectare, sq. meters, etc. - whatever you need.

The accepted conversion factor for ppm to lbs/acre is 2x. So, if you have 10 ppm you have the equivalent of 20 lbs/acre. Your target is 40 ppm or 80 lbs/acre. So, to get to your target you need to add 60 lbs/acre. If you were putting on "pure" nitrogen, you'd add 60 lbs. and be done with it. Since you're using fertilizer that's 8% nitrogen, you have to divide 60 lbs/8% (.08). That's where we get 750 lbs. You would add 750 lbs/acre of 8% nitrogen fertilizer to reach your goal. If you're plot is larger than an acre you'd multiply by 750. For example, 2 acres would require 1500 lbs. I mentioned application rates for smaller plots above. From there, you'll just need to convert to metric.

Nice Job 41-north.

Just to help the poster a little. The ppm to lbs/acre is derived from knowing that an acre of soil, about 6 2/3" deep weighs appx. 2 million lbs.. If you evenly distribute two lb of anything into 2 million pounds of soil you increase it's concentration by 2 parts in that 2 million lbs. which is the same as one part in one million pounds hence, one part per million. Therefore, one can easily use the darned handy 2x multiplier as long as what you are adding is being added in pounds to an acre area of soil for calculation purposes.

41 North didn't detail where the 60lbs. came from, it is from your desired ending ppm, 40 - your starting point 10 ppm = 30ppm. The 30 is then multiplied by 2 = 60 lb..

If you want to get the amount of your fertilizer needed on a square foot basis do the following. First, determine the number of sq. ft. that are going to be fertilized, let's say 870 sq ft.. Next, divide the square footage by 43,560 and get the factor to be used in the next step : 870/43560 = 0.0200. Then, multiply that factor by the 750 lb. that 41-north showed how to get above and you are done. 750 x 0.0200 = 14.98 lb.. So, if you add about 15 lb. of your %8 fert. to 870 sq. ft. of your soil, it's ppm-N should rise from 10 to 40 ppm-N and you will have applied the fertilizer at 750 lb/A, to your 870 sq. ft. plot.

Hope this helps

I would like to thank all of you for this wonderful info.
I am glad that i learned this conversion and the easy application.

To answer michael357 i just wanted to find out how the soil analysts prescribe the amount of fertilizer after a soil analysis.
Is this method credible? Does anyone have any scientific reference for that because i intend to use it seriously.

Anyway

your help was higly appreciated
Panagiotis

What I have always wondered about is how soil varies from the average 2 million lbs. So-called "light" soil is actually less weighty by volume, and "heavy" soil is heavier. A really thick clay might be 3 or 4 million lbs, right? And a light sandy soil might be 1.5 or 1 million, so in a light soil adding x lbs of a nutrient is likely giving a higher ppm of that element, and it is really ppm's that count for plants, I would presume.

Of course, mitigating that is the fact that nutrients leach out of light soils far more quickly than heavier ones.

Nitrogen is the most volatile of the nutrients and is easily lost to the atmosphere and the ground water if the soil has too much as well as interfereing with a plants ability to uptake or properly use other essential nutirents. Most everything I have seen indicates that levels of Nitrogen in soil in the 10 to 20 ppm range are adequate. Putting more into your soil not only wastes your money but can pollute the ground water even more.

Here is a link that might be useful: Nitrogen in soils

Soil test based recommendtions from at least the land grant universities are derived from research. For instance, how much N and in what form (urea, UAN, ammonium nitrate, dairy manure, etc.) does it take to raise the most productive crop of bell peppers commercially. A oils and/or horticultural scientist may partner together from a univ., even with a commercial grower and conduct the research in the grower's field.

Different rates of the fertilizer will be applied and the crop grown in a manner that other variables are controlled as best as possible (irrigation, stand density, etc.). The crop plots are harvested and evaluated and statistics are run on the results. This process must be repeated many times, preferably in many different fields to begin to useful in predicting crop response to applied fertilizer.

I failed to mention that the portion of the field that is used for the experimental plots will be heavily soil sampled prior to the crop being planted and fertilizer added in order to know what is present at the beginning of the experiment.

There really is a great deal more to the entire process but I really don't care to go into it in detail, this is a very rough outline and leaves out a great deal.

Kimmsr: as a friend of mine likes to point out, "It is the water, folks, it is the water..........
If we teach them how to manage irrigation,
then they will be able to manage fertilizer." George J. Hochmuth Professor of Soil & Water Science : Soil Fertility & Plant Nutrition : University of Florida. Any plant nutrient can be lost from the root zone (and further) if it is in the soil solution, if it is not, no leaching will occur. Of course, if the soil gets washed out of a field, it's nutrients go with it, not good. And lest I forget, yes, N and S can be lost to volatilization under anaerobic conditions.

"Kimmsr: as a friend of mine likes to point out, "It is the water, folks, it is the water.......... "
Very true, and if we could "manage" irrigation that might be a possible solution to the problem, but as long as it rains, sometimes torrentially, that means we do not have control of irrigation so excess nutrients in soil will cause pollution of our water.

Yes, I agree, how can one truly "manage" irrigation except in a very arid climate?

I saw this on Amazon for $10 for a 15 lb. bag. It's called "GreenEdge Slow Release Fertilizer with 100% Organic Nitrogen". They claim to be low-salt, made of biosolids - does this mean from waste treatment plant (feces?) This stuff is widely used in golf course.

Below is a link from Colorado State University regarding the classification of biosolids.

Here is a link that might be useful: Choosing a Soil Amendment

There is an enormous amount of irrigation employed in this country ranging from very large commercial ag. fields to lawns, gardens and golf courses, so many places for that potential loss of nutrients to be at the very least reduced.

I was once part of an irrigation demonstration project in western CO, the onion and sweet corn fields were being furrow irrigated using gated pipe and the surge method. One particular difficulty the growers had was getting the water from the pipes to the end of the rows fast enough that it didn't spend too much time soaking downward at the head end of the fields, pushing the water too fast eroded both the furrows and the sides of the beds. When the water made it to the end of the furrows, the water had to be left running long enough to soak laterally across the beds, this was a problem because the head ends had been wetted long before and were beginning to erode and leach downward.

So along came a combination of 2 things to greatly reduce the leaching and erosion problems that allowed much more uniform water application both laterally and downward in the fields. The gated pipe sections in each field was split into 2 sides at the heads, this allowed one side of each field to be irrigated first about 1/5 of the way down and then the water was stopped and moved to irrigate the other side 1/5 of the way down while the wet soil on the other side was allowed to "close up". this pattern was repeated in 1/5s down the field until each side was wet the full length and then the water turned on the entire field to finish wetting across the beds.

This method of wetting and switching back and forth between fields was found to use considerably less water and significantly reduce erosion (soil loss from the field).

And then came an impressive addition to the scheme, polyacrylamide added to the irrigation water, that stuff was amazing. The PA was metered into the head water ditch to allow complete mixing before the water entered the gated pipes at the field heads. Without the PA, furrow water was, of course, like chocolate milk with the soil particles mixed in it. With the addition of the PA, the water was perfectly clear and there was a very small number of 1/16" or less soil aggregates slowly rolling down the furrows. Irrigation cycles now took far less time and used far less water and moved laterally across the beds much faster with absolutely no bed and furrow erosion with the surge+PA combination.

It was interesting stuff to be a part of.

My life has been spent in the parts of the country where irrigation is pretty much mandatory but I do appreciate and understand that mother nature behaves differently elsewhere. To be certain, different tactics must be employed in different places to manage nutrients and soils.