Dr.Antoun,your calculations are O.K provided the NPK recommendation is in terms of N,P,K(not N,P2O5 and K2O).

Dr.Muhammad has to clarify whether the fertilizer recommendation  is N,P,K or N,P2O5,K2O. The nutrients in fertilizers are usually expressed in N,P2O5 and K2O terms.So in many  countries recommended fertilizers to crops are also in terms of N,P2O5 and K2O.

For arriving at weight of soil in 1 ha up to 15 cm one needs B.D.In the absence of the bulk density value,one assumes soil weight as 2 million or 2.24 million or 2.25 million kg/ha.Accordingly the calculated fertilizer amount  varies.

Dear sir

I will do my experiment in china, here the fertilizer are available in  N,P2O5 and K2O form.the main objective of my study is N level. after initial does of 120-60-50 N-P-K, I will add more N to my plants , whereas p and K will be kept constant, so I am confused if I use N-P2O5 -K2 form, how can I go for higher amount of N .

 I understand that the fertilizer N requirement will be  lower in pot culture If you calculate from kg/ha rate.Instead of 120 kg/ha you can even apply almost double the amount,say 240 kg/ha.This amount you can apply in 3 to 4  splits depending on crop growth stages.If it is rice ,you can apply equivalent to 120 kg/ha at transplanting and 60/ha each at tillering and panicle initiation stages.Accordingly you can  calculate and apply fertilizer in mg/pot.You have to apply  micronutrients also in solution form at weekly or fortnight intervals.

So many hanks to Dr Honi Antoun and Dr.Annangi Subba Rao for helping me in calculation.

Muhammed,

Follow Hani's calculation above to add more N to your pot only using the source that you mentioned (ammonium nitrate).

Dear all, I agree with the calculations shown above as far as the maths is concerned. The confusion whether the oxide forms of P and K are referred to or just the elements occurs occasionally. Even the FAI statistics published in India are no exception, with both forms being used interchangeably and only by experience we know that P and K actually mean P2O5 and K2O. Beware of Australian figures, as they have indeed moved to the element form, so K means K indeed.

However, I strongly disagree with the approach as such! Converting fertiliser rates using soil weight tends to give very low applications per pot. Inversely, when deriving 'optimal' rates based on pot experiments and converting them to area-based application rates gives huge numbers that can easily be 5 times higher than anything used in the field! This merely because in a pot experiment you cut off most of the soil volume (depth) a plant would normally explore, while the water supply is usually adequate and would allow for amble growth. This effect vastly overcompensates the much more intense extraction of nutrients form the soil seen in a small pot.

For example, in our experiments using 5 L Mitscherlich pots optimum N rates were 1 and 2 g per pot for safflower and sunflower, respectively.

I'd always recommend going by the pot area, or even better by the expected biomass (size), which closely translates into the corresponding nutrient uptake.

Last but not least, particularly in China, I'd strongly recommend using standard laboratory chemicals for nutrient application in pot experiments. The analysis of, e.g., Chinese NPKs was found to be miles away from the specifications. In other words, a 15:15:15 contains N, P, and K at anything between 10 - 20%! You certainly don't want that in your experiment.

Dr.Gerendas,the points raised by are very important,especially paragraphs 3 and 4.We have discussed the mode of fertilizer calculation in researchgate a few times earlier also, like surface area basis,soil weight basis,crop yield/dry matter production etc.Nitrogen supplementation based  on expected biomass,supplying N,micronutrients at weekly or at regular intervals or at key growth stages for getting normal growth of plants.Your suggestion of Mitscherlich pots appears worth examining for use.In Mitscherlich pot studies , pots of bigger size 5-6 kg or 15-20 are advocated.Nutrients recommended are also high.I find the following presentation online which can be read and suggestions offered by colleagues.

MITSCHERLICH methodology

www.georgikon.hu/tanszekek/.../135-lecture-5-research-methodology

file:///c:/Users/matrix/Downloads/Lecture5_Research methodology(1).pdf

I agree with the point raised by Dr. J. Gerendas in paragraph-2. For conducting pot experiment with rice in the green houses of International Rice Research Institute, Los Banos, Philippines, we (the Soil Chemistry researchers group under the leadership of Dr. F. N. Ponnamperuma) used reagent grade ammonium sulfate, monocalcium phosphate and potassium chloride to supply N, P and K at the rates of 100, 50 and 50 mg/kg soil, respectively.

Elaborate explanations with detailed calculations made the discussion very useful and interesting. I would like to put simple observation regarding addition of fertilizer. Addition of the final calculated small quantity of fertilizer (say less than a gram per 2 kg soil) may be hard task. It's more so for bio-assay of herbicides. We normally follow dilution technique. If, for example, we have to add 1 gram in 2 kg soil, add 10 gram substance to 490 gram soil and mix well. Now take 50 gram of soil+substance mixture and add to 1950 gram soil and mix well. In case of amount less than this, the dilution may be done in one additional steps.

Dr.Kundu,according to your information the N,P and K rates followed at IRRI for rice in pot culture are 100,50 and 50 mg/kg soil.This corresponds to approximately 224,112 and 112 kg N,P,K/ha.If one calculates the  amounts for 2 kg soil

For N  100*2*100/20.5= 975.6i mg ammonium sulphate /2 kg soil(20.5%N in ammonium sulphate).

For P  50*2*100/8=1250 mg =1.25 g monocalcium phosphate/single super phosphate for 2 kg soil(8%Pin SSP)

For K 50*2*100*/50=200 mg potassium chloride/muriate of potash/2 kg soil(50%K in potassium chloride).

The nutrient recommended rates(in N,P and K terms)  followed at IRRI for pot culture are approximately double to those recommended for field experiments.These rates of application appears to be O.K.It is desired to see that the  nutrient status in not high in the soil employed/used for potted study.N need to be applied in splits.The procedure suggested for mixing fertilizer in soil by Dr.Borah appears interesting.

8

Yes, Dr. Rao, you are right. To facilitate normal growth of rice plants in confined soil body (in pots), almost double the dose recommended in open field situation is required. This has been verified by the researchers at IRRI.  And of course, majority of the rice growing soils in south and south-east asian countries are low in nitrogen. Thanks for sharing your opinion on this issue. 

For all practical purposes the weight of surface 15 cm  soil of one hectare is 2 million kg although some take it 2.2 million kg. Two kg soil in a pot is therefore one-millionth of the 15 cm surface soil of one hectare. So a dosage of 120 kg N works out to 120 mg N per pot or 363.6 mg of amonium nitrate. It is not clear whether doses for P and K are as  P or P2O5 and K or K2O. The amount of  P/P2O5  per pot having 2 kg soil will be 60 mg and when the rates are as P2O5 the amount of TSP required will be 130.4 mg. Similarly you will need to apply 50 mg K2O or 83.3 mg of potassium chloride. 

 Dear Dr .Rajendra  Prasad,The calculations shown by you are simple and correct.But the main question is ,do you support  double the rate of nutrient application in pot studies ,compared to field experiments ,to get normal growth of plants?.In potted studies we expect normal growth of plants and response to  applied inputs.We may not give any recommendations from pot culture studies.

Dear Dr. Rao, as I stated earlier plants grown in pots meet their nutrient requirement from confined soil mass only, while plants grown in fields draw nutrients from all sides and deeper layers (subsoils) without any barrier or hindrance. May I refer one of our research paper: Kundu et al. (1996) Soil Sci. Soc. Am. J. 60:1153-1159. It was reported that  rice crop grown in well-tilled field derived more than 40% of their total N requirement from the subsoil layers (i.e. soil layers below the 0-15 cm layer). Other researchers from IRRI, Philippines also estimated the contribution of soil below the surface 20 cm at about 40% of total soil N absorbed by a mature rice crop [Ref: Ventura W and Watanabe I (1984) Philippine J. Crop Sci. 9:135-142]. Therefore one should not wonder that potted plants need almost double the dose of applied fertilizer nutrients (compared to those grown in fields) for normal growth.

Dr .Kundu I agree with you.I have been advocating this practice.

The fertilizer requirements of pot grown plants should not have any relevance to field based fertilizer dosage. The objective behind fertilizer application in field situation and pot  culture is the same, to supply the crop plants with adequate nutrients. Whereas plow layer soil of one ha land area weighs around 2.5 million kg, the mentioned pots contained 2 kg soil only (for how many plants is not known). We must remember that soil is a major source for nutrition, and by applying fertilizers we try to bridge the gap between plant requirement and supply from the soil.  Thus, fertilizer dosage for pot grown plants will in fact must be many times than fertilizer dosage for field situations. If desired, a more elaborate answer can be provided -- but in that case more elaborate information will be needed for the pot culture study.   

In continuation to the above, it is stated that for optimal growth of plants in pot culture (i.e., comparable to optimal plant growth in field situation), fertilizer nutrient requirements must be worked out by considering optimum concentration of the nutrient in various plant parts multiplied by optimal biomass per plant of the experimental crop (to work out total nutrient uptake per plant). Then, fertilizer requirement must be enhanced in accordance with fertilizer nutrient use efficiency in pot culture (which is much higher than field situation). This way, fertilizer nutrient requirement in pot culture will be much-much higher than field situation. A word of caution is that to avoid salinity effect of very high dosage of N and K, these nutrients must be applied in installments (at least 3) rather than a single dose. By adopting such fertilizer recipes, I have had gown vigorous plants of many cereal, legume and oil crops; e.g., maize plants as tall as 12 feet (by growing one plant in 10-kg soil pots).

All the explanations are correct. The best answer, the rate of nutrients for pot experiment is by far exceeded with field ones for any plant species. Mind you in natural soil environment, there has never been as low as 0 nutrient availability. There is always a continous supply. 

You can also refer this article, which is helpful to understand for your doubt.. 

https://www.researchgate.net/publication/269992451_Influence_of_de-oiled_seed_cakes_on_seedling_performance_of_East_Indian_Rosewood_Dalbergia_latifoila_Roxb

Article Influence of de-oiled seed cakes on seedling performance of ...

How can I calculate grain yield of rice in gram/pot? Thanks

 Mr.Thant,at maturity of rice plants in pot,you have to cut the shoot portion (including straw and grain) above ground.First you have to air-dry the samples by keeping them on  clean paper (without contamination).After air-drying, you have to keep the samples in oven at 65-70oC for 24 hours.Periodic monitoring of oven temperature is very important (there is chance of burning /charing of samples if temperature rises high).After oven- drying ,one can determine the total weight(grams) of shoot portion(grain and straw) to obtain dry matter production.Then straw and grain portions can be separated and weighed (in grams).The grain  weight from one particular pot can be expressed in g/pot.

I agree with the comment of Abdul Rasheed that pot applied nutrient does not have any relevance with the field dose. Because small amount causes huge change in the EC of the pot, secondly in pots the substratum would be instead of soil like peat, composte or a mixture of recepe used. In this case the nutrient have to be standardized rather considering the field application. I think particle density and nature of particle entirely changed the picture.

It is true that nutrient uptake by plants in pot experiments is different than under field conditions. In pots roots proliferate well in a small volume of soil and therefore the uptake of native or applied nutrient is fairly high. Pot experiments are only indicative and need confirmation by field experiments.

Pot culture never gives any idea about nutrition requiment and even dry matter production because it is entirely different from field condition. Better way to confirm the study field conditions should be ideal.

Hi, do you know how I can calculate the yield of corn if it was planted on pots? Thank you for your help!

Any published materials (scientific paper) in connection of double dosages of plant nutrients in pot culture than field culture, please? I need to cite the information.

What to talk of double, fertilizer requirements in pot culture are ought to be multiple times greater than in field situations. Some salient published examples are:

1) Rashid A (1986) Mapping Zinc Fertility of Soils using Indicator Plants and Soil Analyses. Dept of Agronomy & Soil Science, University of Hawaii, Honolulu, HI, USA; https://scholarspace.manoa.hawaii.edu/handle/10125/9250

2) Rashid A & Fox RL (1992) Evaluating the internal zinc requirements of grain crops by seed analysis. Agronomy Journal 84: 469–474.

3) Rashid A & Bughio N (1993) Evaluating internal phosphorus requirement of rapeseed, chickpea, lentil and wheat by seed analysis. Communications in Soil Science & Plant Analysis 24: 1359–1369. DOI:10.1080/00103629309368882

4) Rashid A & Bughio N (1994) Plant analysis diagnostic indices for phosphorus nutrition of sunflower, mungbean, maize and sorghum. Communications in Soil Science & Plant Analysis 25: 2481–2489. DOI:10.1080/00103629409369201

5) Rashid A, Rafique E & Bughio N (1994) Diagnosing boron deficiency in rapeseed and mustard by plant analysis and soil testing. Communications in Soil Science & Plant Analysis 25: 2883–2897. DOI:10.1080/00103629409369232

6) Rashid A, Bughio N & Rafique E (1994) Diagnosing zinc deficiency in rapeseed and mustard by seed Analysis. Communications in Soil Science & Plant Analysis 25: 3405–3412. DOI:10.1080/00103629409369273

If i have 2kg soil in pot how much fertilizer should i apply for maize crop

NPK fertilizer???

The amount of fertilizer will depend on the dosage of nutrients. In general , calculation will be as follows:

A dose of 100 kg N/ha is equal o 50 ppm N. Thus for 1 kg it will be 50mg N and for 2kg soil it will be 100mg N. For a NPK fertilizer the dose will have to be fixed on the basis of P dose. Additional N will be needed which can be calculate as explained above.

This is in continuation of respected Professor Rajendra Prasad answer.After calculating the amounts of N, P and K in terms of mg 2 kg soil, one has to multiply with corresponding factors to get in terms of fertilzers.For example to get N requiermeent in the form of urea fertilizer containing 46% N,one has to multiply100 mg N with 2.17.If P reqirement is 50 mg per 2 kg soil, one has to multiply with 5 to get in terms of diammonium phosphate(DAP) containing 20 % P.For potassium if the requirement is 50 mg per 2 kg soil,one has to multiply with 2 in terms of muriate of potassium containg 50%K.Further ,the fertilizer composition is generally reported in terms of P2O5 and K2O.For converting P2O5 to P a multiplying factor of 0.43 is used.Similarly, for converting K2O to K a multiplying factor of 0.83 is used.If one fertilizer,say,diammonium phosphate contains both N and P, the amount of N supplied by DAP may be deducted from the total N reqirement and the balance N amount may be calculated in terms of urea or other source of N.If there is any doubt,please feel free to ask.

Sub aRao is correct

Thankyou Professor Rajendra Prasad

Thanks a lot to all of you - itz quite a learning experience. 1) Please let me also know whether the nutrient requirement be back calculated from the quantity for 'the total plant population per hecatre' to 'single plant per pot' ? Does it make any sense? Please advise. 2) What is the minimum & maximum number of plants to be maintained and tagged for recording observations per pot ? 3) Is it ok to follow destructive sampling for plant tissue analysis to know the nutrient uptake, at different stages of crop period, in the pot? 4) Do the leachates from the pot due to watering also be collected to find out the nutrient loss using lysiemeter technique? 5) Is it ok to fill the water in the tray beneath the pot and allow capillary movement of water upwards to avoid leaching losses of nutrients? 6) What if pots are kept in open space and how can we account for nutrient losses if there are any rains? Regards.

Mr.Niranjan Kumar,I appreciate your questions.But it is important where you are working and what facilities you have in conducting the potted studies.In pot culture experiments the main limitations are limited amount of soil (pot size) ,limited surface area and sufficient and uniform depth.Can you provide sufficient spacing and depth in pot culture to grow the plants similar to field experiments?In very short term studies like the Neubauer test intensive soil exploitation is allowed/followed but in relatively longterm experiments where crop is grown upto harvesting, one has to try to provide conditions similar to field conditions.I do not recommend destructive sampling in pot studies rather one has to have more replications to remove at different growth stages.As I understand only first watering is to be made through capillary rise.Now good systems are there for watering,leaching control or leachate collection.Only one has to see literature,visit to some good university/research institute facilities and also spend money to conduct good quality pot experiments.One can even opt for miniplot experiments in green houses.Controlling growth conditions and weather variables is also equally important in conducting good quality potted studies.

Anyone know the recommended doze or ratio of N,P and K for tomato?

Dr A Subba Rao sir. Why dont we consider the total area of the pot for calculation instead of weight of the soil? In the field we consider the area for the calculation????

We do not consider area in pots because root penetrrstion is much intense in pots as compared to field plots, so the whole soil volume is involved in the absorption of nutrients and water.

Generally if you are using average pots use plant requirement, if not go for the soil volume

how many gram of NPK fertilizer should i apply to a 1kg soil to grow maize in a pot experiment

I like to prepare a ratio of N-P-K is 3-20-20 using 12-61-0, 0-52-34 and 0-0-50. Please guide me how can I find the amount of these chemicals to fix the N-P-K ratio 3-20-20. Thanks.

Fertiliser dosages be applied on plant number basis in a pot experiment especially while evaluating fertiliser effects on crop growth and performance. It would help to correlate the response observed in pot experiment to field trials. Soil weight differs with bulk density and rhizosphere area will change with pot size. Hence it will be most appropriate to apply fertilisers by calculating no of plants in unit a area and apply fertiliser in proportion to potted plants irrespective of media and pot size.

Rao sir I am fully agreed with you. As per as the pot culture experiment so many limitations are there when we compare with field conditions.

Mr.SureshDagade,please try to calculate fertilizer dose in pot and field experiment for a common crop like sorghum or maize using the idea suggested by you to realize the difficulty.Just compute the area for four plants using the spacing recommended (between two rows and within a row in cms) for a particular crop and compare it with commonly used pot surface area.

https://www.slideshare.net/Supta2013/preparation-of-different-agro-chemical-doses-for-field-pot-application?from_action=save