i want us to suppose the following:

My soil analysis reports N (NO3) levels of 10ppm.
My target of fertilization is 40ppm.
I have an available organic fertilizer with 8% N (25kg each bag of fertilizer)- So the actual nitrogen content of the bag is (8/100)*25=2kg

Question:
1) Is there a way that i can convert the quantity of Nitrogen in the fertilizer bag in ppm, and then calculate the amount of fertilizer needed to raise the soils N content from 10ppm to 40 ppm?

Thank you all
Panagiotis

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

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?

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.

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

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.

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

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

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

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.

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

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.