The solution (pH 5.5) is made of mono ammonium Phosphate (300g/100l), Urea (300 g/100l) , Potassium sulphate (300g/100l) + quelated trace elements (100g/100l) .. My concern is on trace elements, K and P absorption as we know urea usually enters fast, but not the others especially P 

The combination of 2,4-D /GA along with nutrients like Fe , Mn and Zn has invariably produced very good response in perennial crops . But while applying foliar spray , utmost care has to be taken , all the spray schedule must be completed before current season  leaves attain maturity .

That's a very interesting aspect , what kind of time interval should we adopt with respect to foliar spray of different nutrients. Such an aspect is most studied for nitrogen , for example , application of low biuret urea  as foliar spray  is absorbed  within less than 24 hours. In foliar spray , the usual schedule is to synchronise the time of spray with crop phenophases. This is the safest strategy to make foliar spray very responsive.

Foliar spray usually should not be practiced , unless there is adverse soil conditions or you need some immediate corrective measure but this will only a temporary respite . We should also not wait for development distinct nutrient deficiency symptoms to apply foliar spray.

15 days. Foliar fertilizer nutrients almost 90% utilized by plant within 15-20 days but depends upon leaf structure, plant age and growth mode. 

Minimum interval should be 12-15 days. Foliar fertilizer nutrients almost 95% utilized by plant within 15-20 days but depends upon leaf structure, plant age and growth mode. 

Independently of being or not a good nutrient management practice (the question is not about if it is or not a good practice), the question is about the time of absorption in order to avoid washout in rainy conditions... I would appreciate answers focus on the question please - Time of absorption, adequate interval to avoid washout. Thank you.

J.M. , I agree with you ,  you have rightly pointed out . In achieving the utmost efficacy of  foliar sprays, most important is , how much time , an applied nutrient  takes to enter into the epidermal cells through cuticle. This is perhaps the most critical issue with regard to use efficiency of applied nutrients as foliar spray. this will off course vary with cuticular nature of different crops , annual versus perennial or monocotyledonous versus dicotyledonous...like that . But million dollar question is , after how much time , an applied   nutrient is not wasted or effectively utilized  by the plants.

The rate of absorption by leaves varies among different nutrients so as the age of the foliage. The younger leaves tend to absorb comparatively more quickly as the cuticle layer is not thick. The rate of absorption may be increased by selecting the suitable time of spray. For example spraying in the sunshine hours would quickly evaporate the solution and will thus slow the absorption. Moreover if the plant is under any stress, rate of absorption would slow down. Addition of a surfactant (Tween 20) to the spray solution   helps in uniform distribution on the leaved due to decrease of droplet size, and hence efficient absorption. In normal cases (N, P, K) one week interval may be safe period.

It depends on type of crop, nutrients being applied and leaf configuration.  Generally, few hours after the sprayed material had been dried out is safe enough.

Fiaz Ahmad mentioned the factors important for absorption of sprayed nutrients, it is a very good explanation. I agree to Dios that in a good shiny day, nutrient sprayed can be absorbed in a few hours. Dr. Anoop Kumar has explained the facts further.   

At least 3-4 sunny days are required to absorb the applied chemical in complete sense.