We should know particular fertilizer mixed with vermicompost. I think majority of fertilizers containing ammonium ions or urea may have such effect. Urea is quickly hydrolized and forms ammonium carbonate. Ammonium ions are subject to nitrification and this process may cause acidification due to liberation of protons.

Dr.Borah,please specify the fertilizer.Is fertilizer mixed @24% in vermicompost and 10% farmyard manure?Whether they are applied to soil or not ?How long the incubation was carried out?

Nilay , lets also consider the initial microbial load of the vermicompost versus FYM in bringing the faster transformation in pH value of the end product , however I do not know  the period for which such mixture were exposed for such results.

Dr Rao sir and Dr Anoop sir

1. Same amounts of urea (81 kg), single super phosphate (187.5 kg) and muriate of potash (50 kg) were mixed with 2500 kg of vermicompost and FYM each.

2. The pH was measured within one hour of mixing.

3. The pH of the vermicompost reduced by 10% from its initial value and that of FYM reduced by 4% from its initial value.

4. The Azotobacter, Azospirillum and PSB population in vermicompost and FYM was about 5.4 to 10.2 (-log x 10^5 cfu/g soil) before mixing the manure following 15 days incubation (@ 0.2% w/w) with the microbial cultures.

Thank you for your suggestions

Dear all, single superphosphate contains also some phosphoric acid (5% or less). Could you provide the particular values of pH of vermicompost after and before mixing? And the moisture content of vermicompost and FYM?

Dear Michal

Thanks again for your inputs. This time we'll measure pH of the individual fertilizer before mixing too, that's a good point.

In our experiment the pH of the vermicompost was 6.65 and 5.96, and that of FYM 8.25 and 7.95 before and after mixing, respectively.

The fertilizers added and the amounts added are same in case of both vermicompost and farmyard manure.The important point is that the farmyard manure resisted change in pH better than vermicompost .Possibly, the humus content is more in farm yard manure than in vermicompost and so FYM has more  resisted change in pH (buffered )compared to vermicompost.The vermicompost is finely divided and many carry with it some organic acids and enzymes from gut and so its pH is lower than FYM .I do not know about the amount of humus in vermicompost. The humus content depends on the cooling or maturation period allowed after thermophilic  and second low temperature phases in manure composting and excretion of vermicasts from gut in case of vermicomposting.

Nilay , with your interesting results , which of the two organic manures , we can declare biologically more active. Possibly , vermicompost , by the virtue of much narrower C:N ratio plus better microbial load will be more crop responsive than FYM.

Dr Rao is correct. FYM resists more to change in pH than vermicompost.

Dr Anoop, our observations conform your statement. But the recent observations are interesting, and we would say that the efficiency would depend upon crop. We found rice, wheat, chili, tuberose, marigold respond positively to vermicompost-fertilizer mixture, but not tomato. In tomato, FYM-fertilizer mixture was best. Again, in case of rice DSR performed better in coarse to medium textured soils than transplanted rice.

Thanks to all.

In my opinion, FYM (at least, the fresh FYM) might be more active from the biological point of view. Vermicompost is quite stable, as the end product of many changes. Contrary, the fresh FYM is a mixture of litter (straw? wide C:N ratio) and animal products (narrow C/N ratio, i. e. it is a starting point for microorganisms. During microbial changes, ammonification occurs and ammonium produced during this process combines with some acid components of single superphosphate and may be this is an explanation, why FYM changed it's pH less, than vermicopost? On the other we must remember, that to compare both materials they should have the same pH. We know, pH is a logarithmic scale, so FYM with pH of about 8 contains 10 tmes less H ions, than vermicompost with pH of about 7, and 100 more, than vermicompost (or any other material) with pH 6. So, this buffering capacity of FYM is even more evident.

Dr.Stepien,I agree that we can offer different reasons based on the material in question i.e whether the manure is fresh or composted.

Dr Stepien, we will take into considerations your points in future studies, I too have little inclination towards that thought. Another point coming to my mind (we have not yet estimated it) is whether the specific surface of the two manures has anything to play a role!!

Nilay , agreeing to your all interesting results and the responses  from other colleagues as well , how to decode the underlying mechanisms of such differential responses , where the physical properties and chemical behaviour of these two organic manures are so heavily involved , besides the nutrient-microbe synergy.   

The nature of chemical fertilizers should be the controlling factor. For example, only some fertilizers lower pH when added to soils.  some similar should apply here..

Thank you Bijay Singh Sir!!

We think this is an area we need to work little more. We tried mixing lime (CaO) with composts, FYM (with pH 8.06) outperformed vermicompost (pH 7.12) and recommended practice in tomato. This again hints at higher buffering capacity of FYM. Again there may be crop specificity and soil moisture regime effects.

Nilay , in addition  to  what Prof Bijay Singh has correctly pinpointed ,  we also need to trace the underlying mechanisms of some  microbes( We popularly call them rhizocompetent microbes isolated from within the plant rhizosphere) being  so comfortable against chemical fertilizers (I am not specific with any fertilizers) . Don't we think, efforts are also needed to exploit upon such synergy  for the betterment of soil health in terms of both nutrient  as well as microbial pool of the soil  vis-à-vis crop performance .

A K Srivastava sir your observation is appreciable. Some work must be initiated. Thanks

Dr.Borah,you have measured pH of the FYM and vermicompost one hour after mixing .It means that you have not allowed sufficient time for urea to act on manure/compost to reduce pH .Muriate of potash may not reduce pH of  manure/compost.So, it is single super phosphate containing some free acid which reduced the pH of FYM and vermicompost (also pointed out by Dr. Stepien).The pH reduction in FYM was less than in Vermicompost implying that the FYM offered more resistance/ buffering to pH change. than vermicompost possibly because of high CEC of the humus in FYM. So I advice you to determine the cation exchange capacity of both FYM and vermicompost to explain the reason.

Dr Rao sir, thanks for your comment. We will estimate CEC of the composts used. Further, specific surface of each compost may also be useful.

Dr.Borah ,you can do surface area also if you have facilities available.

Thanks

Dear Nilay, when mixing lime with FYM, remember, that the lime may favour volatilization of ammonium, produced during microbial processes. So it is important to measure it (if possible) and to elaborate a way of mixing with lime to avoid such situation. Or not add lime to FYM - probably it is not necessary in majority of cases.

I am not too sure , whether Nilay , you mixed any lime with FYM . Its urea , superphosphate and muriat of potash mixed with both the sources of manures , FYM and vermicompost ?

Michal , could you say FYM has more recalcitrant from of carbon than vermicompost ?

I think NIlay mentioned it in one of comments.

Anoop, I am not sure what you mean in your question?

Colleagues, these are separate works. The mixing of lime with FYM or with vermicompost was evaluated in tomato, wheat.

Mixing of chemical fertilizers (urea, SSP, MOP) with FYM or vermicompost was evaluated in DSR, transplanted rice, tuberose, marigold, wheat etc.

Sorry Anoop, my English is not very good, that is why I am asking.

Michal , i mean to say , would you say that carbon in FYM is in more stable form (Recalcitrant , more resistant to further decomposition ) than the carbon in vermicompost , and , thereby , greater intervantion of microbes participating in decomposition of decomposable carbon in vermicompost.. And , therefore , vermicompost is microbially more active than FYM?

Anoop, no, I think, that the carbon in fresh FYM is much less stable, than in vermicompost, or in any mature compost. Fresh FYM is the mixture of litter (mainly straw, but not necessarily), feces and urine. These two substances mentioned are rich in nitrogen and in great part in form easily available for microorganisms - urea, other aminoacids from urine, digestive enzimes. For this reason I think, that fresh FYM perhaps is not rich in microbes, but they found very good substrate for growing and multiplicate very quickly.

The vermicompost, and any other composts are rather final product of many processes. I think, it is composed of "true" humic substances, such as humic acids and humins (salts of humic acids), and other, rather resistant to decomposition. So I think, that the vermicompost is much more stable than the fresh FYM. Certainly, vermicompost, may contain more species of microorganisms, than fresh FYM, but these microorganisms probably are in spore forms or hibernated in any other way, because they have nothing to "eat".

Sorry, I am not microbiologists, I simply write what is obvious for me.

We do observe similar results as had been suggested by Dr Stepien. The population of bacteria was higher in vermicompost than FYM. Besides, FYM had higher C:N ratio implying presence of more decomposable carbon than vermicompost.

Regarding mixing of lime with FYM, I borrowed the idea from traditionally followed farmer's practice for long time. Initial hypothesis was the potential reduction/neutralization of acidity/organic acids in relatively immature FYM by lime. But, as observed FYM had higher pH than vermicompost, and higher buffering capacity. So, the positive effect of adding lime with FYM needs to be looked from different angle of study. Your views are welcome.

Well decomposed composts(probably up to at least 3 months) and composted manures may contain more humic  substances.Partially decomposed manures and vermicomposts(up to 17% humus according to one reference) may contain less humic substances.Microorganisms may prefer the easily decomposable materials with a C:N ratio of less than 30:1.As mentioned by Dr. Borah,vermicompost  may contain more microbes than in farmyard manure.But fresh manure also can invite more microbes before its C:N reaches 15:1 or so.

Nilay , such positive effect of lime addition to FYM , has to be looked into from the angle of  higher pH needed in those highly acidic soils.Where from higher bacterial population come from , simply due presence of more unstable form of carbon ( Part of labile fraction  or non-recalcitrant carbon vulnerable to microbial decomposition) present in vermicompost , which you do not find in FYM. This is where , i was addressing to comments from Michel , why FYM is able read higher pH because of lesser degree availability of carbon from FYM than vermicompost. 

Dr Anoop, thanks for your observation. That is what we also think and wanted views from experts. These can not be generalized, our work has just started and results may vary in soil types (as mentioned by you) and crop species.

Dr.Borah,agree with you.We can discuss more on the data generated in future.Now simple/easy to handle methods are available to determine labile/active carbon and also humus(not elaborate humic acid fraction procedure).So one can easily estimate active/labile carbon and humus in manure and composts to resolve the issues or get more clarity.Best wishes.

Dear Sir'

The pH of vermicompost is just closer to neutrality and when we add chemical fertilizer in vermicompost it will shift the pH of the mixture towards acidic range due to presence of certain inorganic components in the chemical fertilizer. 

Thank you Dr Rao and Dr Singh sir