Application of a mixture of FYM+ Quick lime (CaO) + woodash (1000:10:1 w/w) @ 1 t/ha may be tried. We observed significant increase in availability and uptake of P by dry seeded upland rice, baby corn, wheat, tomato, greengram (Vigna radiata), taro (Colocasia esculenta). In case of crops with duration more than 70 days, two applications at sowing/planting and another after one month may be required depending upon the soil fertility status.

Hello Peter,

It depends on the type of soil you're working on. Remember that Phosphorus availability depends on the soil texture (different types of clay can retain different amounts of P, and in general clay retains more P than sand) and also on soil pH, among other factors.

As mentioned by Nilay, including lime or other substance that increases pH (in case your pH is acidic) is crucial for P to be available in forms that the plant can absorb. It is generally accepted that P availability depends on soil pH, and usually a soil pH between 6-7.5 is needed for maximum P availability (see paper below). When you go to more acidic soils, P is bound to Aluminium and therefore inaccessible by plants. If you move towards more alkali soils, P is bound to Calcium.

http://www.sciencedirect.com/science/article/pii/S0883292709002625

http://nmsp.cals.cornell.edu/publications/factsheets/factsheet12.pdf

There are also bacteria (Azospirillum, Pseudomonas, etc) that can increase P solubilization in the soils, thus enhancing P availability for plants.

http://www.sciencedirect.com/science/article/pii/S0944501306000589

Hope this is helpful.

Cheers

Appreciate the observations by Jose Martin. The suggested mixture is for acid soils only. Thanks.

 Best regards

The assimilation of P depends on the type of clay, amount of clay, time of application, aeration, compaction, soil moisture, type of P species, temperature, pH and interaction with other nutrients. Phosphorus is found in soil in several species but is assimilated by the plant into two forms or species such as primary orthophosphate (H2PO4) ^ -1 and as secondary orthophosphate (HPO4) ^ - 2 each is more assimilable depending on the PH of the soil solution so the primary orthophosphate is more assimilable in acidic pH and the secondary orthophosphate is more assimilable at alkaline pH, at pH 7.2 the two species are assimilable. That should be taken into account to determine the availability that I have on the ground. Also the type of soil is important especially if it is an Andisol or organic soil the phosphorus is retained strongly limiting its assimilation. Although it is true that solubilizing bacteria do a good job of solubilizing P in an Andisol are limited because the bacteria releasing P, this is quickly retained by this type of soil. The interaction between nutrients should be considered. My recommendation would be to put supplemental fertilization via foliar. It should be taken into account that absorption time depends on the type of fertilizer that is being used to be absorbed 50%, so salts and oxides of P takes about 15 days after being applied, synthetic chelates takes from 7 to 11 days of Be applied, or organic chelates of amino acids plus proteins take less than 2 hours. I hope this information has been useful, I say goodbye.

The mobility of a nutrient will determine the method of application and uptake by roots of crops ,therefore, phoshorus is an immobile nutrient and must be applied either in band or ring method for proper utilisation by crops also,nitrogen is a mobile nutrient and can be applied through broadcasting method or by band method because it will reach the crop wherever it is placed and can be leached downwards to pollute underground waters.In addition, micronutrients such as Fe ,Zn ,Mn ,Cu can be applied through foliar method because they have strong ligands and chelating properties characteristi.c of d orbital elements

Besides my earlier answer to this question I want to suggest the use of mycohriza symbiotic relationship involving soil fungi fixing P into soil for roots uptake ,this is very important because most of phophate fertisers Single super phosphate [SSP] ,Triple super phosphate [TSP] and others are very expensive to be purchased by farmers and destroy soil properties on continuous use ,therefore, the use of biological method of fixing P into soils combined with use of organic manures such as poultry ,goat, pig manures will enhance sustainable soil productivity and bumper crop yield and this is the basis of soil fertilisation principle .This principle will ensure soil fertility with high residual effects which can support the growth of many crops [multiple cropping] instead of conventional crop fertilisation principle which supports for specific crop fertilisation mainly monocropping and cause soil nutrint depletion .This explains why most farmers prefer to practice multiple cropping involving many crops to act as cover against soil  e,rosion , increase soil organic matter and increse soil pH  and reduce P fixation

In addressing Phosphorus issues we need to understand P is relatively scarce and the most expensive major nutrient. The proliferation of mycorrhizal colonization can increase the root system extension hundreds to thousand of times compared to non mycorrhizal plants. The attached graphic shows that the dose of optimized plant reaction can be achieved at 25% of the optimum dosage when plants are nonmycorrhizal. The ability to use mycorrhizal inoculation and changes of the management of the crop system can enhance mycorrhizal proliferation to give game changing results in respect to Phosphorus issues. Biology and chemistry are both needed to optimized our limited Phosphorus resources. 

In addition to band placement, inoculation of phosphorus solublising microbes will help to enhance the phosphorus use efficiency in the soils. There are several proven methods for acid soils too.

The ability to strategically apply phosphorus directly to plants at critical stages may be a strategy which requires less application of total product improving costs and lowering the issues with over phosphorus in the  environment leading to eutrophication.  This might be a good venue for utilizing solubilized phosphorus in foliar application and venturi application directly to the root system.