Dear Mera

You can read these files.

Regards

Ahmad

 I think the references given by Mr.Solgi ,especially the first one provides a good description of the Neubauer  method.In short time the maximum  amount of P or K is taken by the test crop because of more population,root colonization of soil and greater exploitation of soil volume in Neubauer cup.So it can provide an estimate of plant-available nutrients in soil.As shown in the reference one attached,the micronutrient uptake in short period may be small.Controlling growth conditions ,moisture,temperature and humidity may be important.The following two references may be consulted for details of other short time studies on P and K absorption from soils.

Potassium status of soils:Significance of the"Italian ryegrass test" 1984 by Binet,P. ;Guessabi,L.el and Salette J.J.Fertilizer Research,5:393-402.

http://link.springer.com/article/10.1007/BF01049119

A method for measuring short-term nutrient absorption by plants:1.Phosphorus by Stanford,G. and Dement,J.D. Soil Science Society Proceedings 1957 pages 612-617.

Here a comment from the "Neubauer" Country: its useful only if you check different soils just always under the same experimental protocol. The data itself have no ownstanding meaning! Ist a nice "mini-pot" experimental control we still use from time to time!

I agree with the good comment of Dr.Schnug.Even in recent times, I find the use of the Neubauer test or the Italian rye grass test to know the plant-available soil nutrients or potential supply of nutrient like K from mineral source.If resources are available or not a limitation, we have a lot of new soil and plant tests to assess the nutrient status of soil,see respone to applied nutrients(which we not get through Neubauer test) and monitor soil fertility over time  to adjust nutrient application rates and to avoid soil contamination through excess nutrient ions or heavy metals.

Thank you all for your contributions. Mr. Subba, so in order to see effects of the nutrient availability of different soils, is it necessary to let them grow until exhaustion, or between 14-21d is enough to watch some effects? Herr Schnug, when you refer to the same experimental protocol, you mean that all the pots and soils are submitted to the "same variation factors" and same conditions of a fully randomized design? 

 Mr.Josue,for nutrient like phosphorus growth period of 21 days with more population of plants is adequate.For nutrients like potassium,the immediately available K  from water soluble plus exchangeable source and long term K supply from nonexchangeable K source (especially in soils having high amounts of micaceous minerals) are important.So for K, Neubaer test and a repeated exhaustive cropping with a cereal like rye grass or legume like alfalfa are needed.

Mr. Subba, thank you for the valuable information. This is actually one of the main points I wanted to have clear, in respect to the length of the experiment. Another part is when harvesting, removing the whole plant material can be a difficult task, specifically in the removal of soil:sand from the roots. Is there any "appropiate" form to take away the soil from the roots?.