If fresh soil is taken instead of dry soil, do we have to take water content of soil specimen to KCl extractant volume in final calculation i.e. Total volume for calculation = KCl volume + water content of weighed fresh soil?
Yes, you will have to take into account the water contained in the soil sample for calculating the KCl extractable nitrate+ammonium in the soil. The amount of water contained in the soil sample will have to be added to the total amount of KCl solution used for extraction. This will allow to estimate total mineral N in the extractant solution. And finally calculation will have to made on the basis of dry weight of the soil sample, which you will be able to work out easily as you are going to determine the moisture content in the fresh soil sample.
The bigger issue is that, if you weighed the soil, there will be a difference between the fresh weight and what it would be if it were dried. This may make a large difference in the final result.
@ Bijay Singh and @ Salvatore S. Mangiafico : Thank you sir for your reply.
I totally agree with Dr. Singh's comment on moisture correction. One thing I would like to add is to considering the fresh soil weight. For example, 5g fresh soil is usually extracted with 25 ml of 2M KCl solution. (depending on soil type the concentration and volume may change).The volume of the KCl usually remains constant if you are adding with a dispenser where you can set the exact volume needed by calibrating the dispenser. In contrary, weighing exact 5g soil is difficult. Therefore, I will recommend you take the exact soil weight into consideration for each soil sample while you will be doing your final calculation for KCl extractable ammonium and nitrate. Hope this helps.
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