Dear Dr Sagar, very nice interpretation undertaken, it may be due to dried sample may lost nutrients particularly becouse of heating.

Greetings colleagues, as we know, one nutrient or element like a metal could be in diferents fractions, as an oxide, in a complex (in the organic fraction when the system, soil, have ligands), in the structure of a mineral phase, as a carbonate or water-soluble. We could do a secuencial extraction to find the diferents concentration in each fraccion, or find the total amount of element. I think its true that when you dry the soil moisture it could lost it´s water-soluble fraction. Let me ask to my colleagues from de soil laboratory, however I think that your hypothesis it´s right.

Dear Dr. Sagar SUBHASH More

Heating of the soil sample is required only when you are concerned about the available nutrients bound within the humus and colloids. Mostly transient compounds such as nitrites, ammonium ions, phosphates which are dependent on the pH of the soil are changed rapidly during heating. Air dried soil does have all the stable nutrients retained but in soil chemistry we mostly look for the available nutrients in all their forms and that has a huge bearing on the dissolved nutrients withn the pore water which gets totally eliminiated through oven drying (not at all recommended) or even air drying in higher ambient temperature. The temperature should never exceed 35oC and at 60% relative humidity at minimum. Rapid measurement of soil volume and then transferring it to a chemical extractant such KCl or NaF presvents the conversion of many elements like N and P. One should only be concerned with soil moisture when he/she is trying to get the nutrient content per dry weight units but the nutrients in soil available to organisms are both present as bound to substrates as well as dissolved fractions within the interstitial water and are never actually physically dry apart from specific sites. The need of soil samples to be analyzed, the process followed in sampling them, the handling of the samples once they arrive at laboratories, the method of extraction followed all have their respective pertinence on the outcome. What your need is governs the results, that all.

Regards,

Dr. Abhishek Mukherjee

Thanks Abhishek sir

I must highly appreciate your points because you have given many things regarding the analysis.

Thanks

Regards

Sagar

Plant-available nutrients need to be analysed on air-dried samples passed through 2 mm sieve(moisture has to be estimated). Drying a wet sample may increase or decrease the available K content, depending on the initial K content and mineralogy of the soil. Summer and winter temperatures influence the available P concentration in the sample.Maintaing the Lab temperature at around 25o C is desired. Protocols differ for different nutrient elements or their ionic forms and under certain conditions like sampling from flooded rice field. Samples for microbial /microbiological analysis and nutrient transformation studies have to be analysed on fresh samples or samples stored for very short time at low temperature like -4o C. For total elemental analysis one has to oven-dry the sample to drive off the moisture completely.

I agree with Dr Angani

It is prefatable to go shade drying of soil while determination of available nitrients .

Yes, I strongly agree with Dr Manpreet, but is there any moisture effect on nutrient content affect adversely on estimation. Even, shade drying remains mositure in soil.

Thanks alot to all

Actually in standard procedure we have to use air dried soil sample but u have asked question quite differently.

My purpose was to check whether the soil infield and in lab shows the same properties.

Because when I tried one sample for P estimation in that I got the variation in the air dried sample value and without dried sample.

That I want clarify whether the moisture in soil plays role in the nutrient availability.

That question raised in my mind due to one incidence regarding the mango fertigation during summer.

In month of March to April moisture in the coastal Konkan soil is very less so even though the available nutrients are present in the soil but it could be taken up by the plants because of the moisture deficit condition.

But at the same type when I observed regarding the estimation of P from submerged rice the available P in wet condition it shows the more reading than when I air dried that same sample and took the reading.

That means we are manipulating the reading by drying that sample.

That is my purpose to ask this question.

At last I do agree with all of you that we have to follow a standard procedure.

Thanks alot for your valuable discussion.

Regards

Dr Sagar More

Dr Sager proud of you, very nice observe during experimentation and this is happen, as I know for microbial count we need to use soil sample for few hours. Likewise in your observation fruitful findings will be in due course of time.

In wet samples there is possibility of volatile phosphorus compounds usually formed in soils rich in microbes, they get evaporated while drying, that is why your observations.

Dear colleague,

in order to analyze the P-available in your soil samples, you have several options depending of your objectives 1) to determine the P content in the samples after dir-rying and sievieg (2 mmusing standarized protocols; 2) to apply a SEP (Secquential Extraction Procedure) in order to obtain the soluble and exchangeable fractions; 3) BAay and Kurtz method (better for acidic and neutral soils); 4) Mehlich 1 Method (soils pH5%); 5) Mehlich 3 Method for all soil types and a good method for agricultural soiols; 6) Olsen Method , very popular and a standarized method. 7) Burriel - Hernando Method for calcareous soils or soil with high pH (it is based on the Olsen Methods).

Regads,

Rocio

Thanks alot to all for giving their important inputs.

Thanks

Regards

Sagar

Very well described by Dr. A,Subba Rao. Just follow it.

I agree with Dr Subba Rao.

The available nutrient limits being followed by various agencies are on the basis of soil dry weight. It will vary for different elements. e.g. determination of mineral N (nitrate and ammonical) should be done on moist weight basis. Most part of P is insoluble; so in your case moisture in the soil would have solubilized P, thus leading to more extraction. Also there should not be variation in soil-extractant ratio while determining elements on dry or wet weight basis.

Analysis of P content in air dried samples better linked with field conditions for P fertilizer management. If samples are dried in oven at 110 degree Celsius for 24 hrs, its availability (citrate soluble P) is decreased because the P is fixed with Al/Fe hydroxides in acid soils and form octa-calcium phosphate in alkaline conditions.

Water (in this case moisture) even in its neutral state carries charge (positive in hydrogen atom and negative in oxygen atom) due to sharing of electrons closer to the oxygen. P or other nutrients when present in form of ions in soil are held by water molecule due to this charge. This is the main reason that moist soil tend to contain more nutrients. For more information regarding this please refer "The Nature and Properties of Soil by Brady and Weil"