My crop need 80 kg/ha of P and in my soil we have 10 ppm of P.
Good Day Angel. When calculating fertilizer requirements, a number of things are considered:
- Firstly Expected Crop removal: - Crop tons expected (or required) x Typical Kg P in a Crop Ton (We must replace that which is physically removed)
- Secondly Application Efficiency - How much do I need to apply to get the P removed by the harvest into the plant.
This uptake efficiency is again influenced by a number of things:
- Firstly: What is its ratio to other minerals as this might lock the P and limit the uptake.
- Secondly: What is the total Available P in the soil. If the soil has excess P we might be able to "mine" it for a season or two. If the P ratios in the soil is unfavorable we might want to make soil amendments first (maybe add P to the soil) in order to correct the ratios so that the uptake happens as we expect it to, when we do the application. We make soil amendments if the P is below 50ppm P (Bray1) if carbon% is below 1 and also if P is below 25ppm if Carbon % is above 2 We also make amendments or adjust application if the P/Zn ratio is not in the region of 10/1
- Thirdly: Adding a carbon to your P at application will greatly improve the application efficiency (Humic or Fulvic Acid) I have added a graph showing long term analysis of P application in Citrus orchards, which shows that significant cuts can be made in P application by adding a good carbon without undermining leaf P levels (i.e this improves application efficiency)
- Fourthly Soil biology can greatly improve P uptake and unlock the locked P in the soil. Applications of carbon, mycorrhiza and soil phosphate solubilizing bacteria assist with this process.
To make it practical then in your case:
Forgive me if I'm stating the obvious
Dr.Angel Marcelo ,please mention the extractant used for estimating available P in your soil.In your country,do you follow some ratings or critcal limits to group different soils low,medium and high or adequate/sufficient or deficient in P (in general or crop specific) or some calibration chart connecting soil test values with fertilizer P recommendations for different crops.You may also mention what source of P you desire to use .
Angel , it is equally important to take note of what is the present yield level and what yield level , you are targeting at . And , do you have any soil test -based fertilizer equation for any of the crops grown in your region . That is very important .
if your soil P content is considered to be sufficient supplied by the method you employ for analysis and the soil is "healthy" says with proper structure and OM content then you fertilize exactly what you remove with your harvest products, but always as watersoluble P! P fertilizing is not a myth :-)
Dear Angel Marcelo.
Weight of soil in a one ha approximately 1300000kg (soil depth 10 cm, bulk density 1.3 g/cm3
10 ppm that’s mean 10 mg /kg then 1 hectare has 13 kg P
Your crop need 80 kg / ha P (80 -13 = 67 kg phosphate per hectare)
Now what is type of phosphate fertilizer you want to apply? it is important to know type of fertilizer for example you want to apply NPK or Diammonium phosphate etc. After that we will calculate how much kg of fertilizer you need to apply to get 67 kg P per ha
Dr.Rawashdeh,Your calculation is O.K.But we are not supposed to do like that.There are three approaches to do.
If your soil is responseive to P fertilizer application(10 ppm Olsen's P indicates medium P status and crop may respond to P)),then you have to provide the entire amount of recommeneded P(80kg P/ha) through diammonium phosphate or any other soluble P source(mulptiply P requirement with100/P content in fertilizer).
The second alternative is as suggested by Dr.Schnug.
If your soil is adequate in available P(say >10 ppm Olsen's P),If you know the amount of P removal by the crop,then add P through fertilizer equivalent to P removal.
If you have a calibration table connecting soil test values and corresponding fertilizer recommended ,then based on your soil test value you can apply recommended fertilizer dose through any soluble P source.
Dr ANNAGI. SOIL ANALISIS WAS OLSEN, THE P-FIXATION IS 80% AND FERTILIZAR USE EFICIENCIE IS 10%
Good Day Angel. When calculating fertilizer requirements, a number of things are considered:
- Firstly Expected Crop removal: - Crop tons expected (or required) x Typical Kg P in a Crop Ton (We must replace that which is physically removed)
- Secondly Application Efficiency - How much do I need to apply to get the P removed by the harvest into the plant.
This uptake efficiency is again influenced by a number of things:
- Firstly: What is its ratio to other minerals as this might lock the P and limit the uptake.
- Secondly: What is the total Available P in the soil. If the soil has excess P we might be able to "mine" it for a season or two. If the P ratios in the soil is unfavorable we might want to make soil amendments first (maybe add P to the soil) in order to correct the ratios so that the uptake happens as we expect it to, when we do the application. We make soil amendments if the P is below 50ppm P (Bray1) if carbon% is below 1 and also if P is below 25ppm if Carbon % is above 2 We also make amendments or adjust application if the P/Zn ratio is not in the region of 10/1
- Thirdly: Adding a carbon to your P at application will greatly improve the application efficiency (Humic or Fulvic Acid) I have added a graph showing long term analysis of P application in Citrus orchards, which shows that significant cuts can be made in P application by adding a good carbon without undermining leaf P levels (i.e this improves application efficiency)
- Fourthly Soil biology can greatly improve P uptake and unlock the locked P in the soil. Applications of carbon, mycorrhiza and soil phosphate solubilizing bacteria assist with this process.
To make it practical then in your case:
Forgive me if I'm stating the obvious
Klaus very impressive explanation . Our major limitation comes in the way , how to demarcate a given soil test value is , whether low or high for a specific crop to be grown . And a given soil test value is low or high for what target yield , needless to say , soil test value is so dynamic that , what soil test value is high for a given yield , could be low for a much higher yield that is targeted.
Dr.Ferreira,I compliment your very detailed reply.Dr.Angel Marcelo,you did not mention the soil pH and also the crop.While P fixation appears to be high ,the P use efficiency is quite low.AvailableP/Olsen P of 10ppm is O.K.(as per Indian rating it is adequate for crops(10 ppm P=22.4 kg P/50kg P2O5)).If quick growing crops are grown under irrigation we can expect good P use efficiency even in the so called high P fixing soils.Organic manures can further facilitate P mobiliztion and extend the period/duration of P availability in soil.
Dr.Angel Marcelo
To calculate the ammount you must take in consider many things,Growth habit of the crop,soil pH,ECe of the soil,application method(soil,or foliar applied,DRIS chart for the crop,and the nutrients balance in the soil.
Warm wishes
Ali Alhayany
En effect too many things. Soil pH is important, but I consider that 10 mg P/kg in many soils are just in the limit of low to medium contents. Please check by a simple P-fertilization test in pots.
Dr. Klaus. I have every parameters.
Fertilizer use efficiency 10%, determined with P-32 method
Total Absortion P, 80 Kg/ha.
Soil analysis P Olsen 10ppm
pH of soil , 6,7
MOS 3%.
How much P we needd aplied?
Dear Marcelo, what is the fertiliser or source of P you'll use to supply the required P to your crop?
Macelo, with the almost neutral pH and a relatively high content of SOM, I do not understand why the fertilizer use efficiency is so low; as Dr. KUNDU says, what is the fertilizer source for P...?
Thank you Dr.Malhotra and other colleagues.Every country has to develop its own soil test crop response calibration system to recommend fertilizer,fertilizer plus manure(integrated) or manure alone (organic farming) for different crops .Dr.Schnug suggested the replacement crop removal approach of P fertilization.Mr.Klaus Ferreira has provieded a detailed and step by step account of how to achieve such recommendation.At IISS our team worked on this approach to generate recommendations for soybean -wheat system following the strategies of fertilizer,fertilizer plus manure and manure to meet the P requirement of the crops in Vertisols having 5.84 ppm P(Olsen),When manure alone or manure plus fertilizer are applied, it is just sufficient to replace the crop removal of P from the soil.But when we apply fertilizer alone we have to add an additional amount of P to satisfy soil P sorption/ fixation reactions and make sufficient amount P available to crops.When soil test values of P improve to adequate level, one need not apply additional amount of P.
Organic manure based phosphorus supply strategies:Effects on crop yield and soil test maintenance P requirement under soybean-wheat system.Biological Agriculture and Horticulture 24(1):21-34 January 2006.
http://www.researchgate.net/publication/254214833_Organic_manure_Based_Phosphorus_Supply_Strategies_Effects_on_Crop_Yield_and_Soil_Test_Maintenance_P_Requirement_under_soybean-wheat_System_
Article Organic Manure Based Phosphorus Supply Strategies: Effects o...
There are already nice and details measures for fertilizer P calculation. I would consider (1) what is soil available P for the crop/season, (ii) what is soil pH, (iii) what is your yield goal (i.e. expected yield) and calculated P removal for the yield, (iv) what are other sources of the nutrient in question (e.g. organic amendments, other supplements etc. and (iv) finally, calculate the net amount of P that should be added to balance the budget. Considered all soil P and added P are not readily available for the crop!
To calculate the amount of fertilizer you need a calibration curve for each species, and if possible region (soil type - P, plant age, extractant type, etc.)
Dr. Moreida. Do you have information abaout FERTICALC program used in Brasil for recomendation of fertilizer
The FERTICALC program is used for some specific crops, such as banana
Dr, Moreira. Could you givme a program FERTICAL BANANA
Dear Marcelo
I do not have the FERTICAL BANANA program because it is paid
Dr. Klaus Ferreira. Do you need more data to calculated the requirements of P ?
Dr.Angel MARCELO,Please go through the following well illustrated paper for developing soil test based fertilizer recommendations(involving all the steps).
Developing a soil test extractant:The correlation and calibration processes.
By Hochmuth,G.,Mylavaru,R. and Hanlon Ed. University of Florida IFAS Extension
https://edis.ifas.ufl.edu
You discover a real thing Angel Marcelo CALVACHE: There not relation between fluxes and pools, even in soluble cations. As an example, you can have a reduced flux of N because either the demand is very high or the pool is small (or both). For that, the best approach for solving this problem is performing a biogeochemical balance of N. You answer could be: ' But we need a lot of data!'. Yes, it is true, but an 'available' N is only an instant photograph, no a dynamic process as the Nature is working...
Estimado Juan. Si el análisis de P por Olsen en el suelo te da una reserva, como podríamos transformar en un flujo. Por ejemplo si existen 10 ppm de P en el suelo, un cultivo de pasto podría tomarlo en un año a una taza de 0,027 ppm/día.
If it is perennial crops , better to use leaf analysis -based fertilizer recommendation.
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