Nitrogen requirements of many crops is much higher than the N  one can apply through foliar application. Because of this reason it may be difficult to suggest different  rates of foliar application to different crops.A 2% urea solution may be safe for many crops. Normally 2-3sprays are recommended ,at crop growth stages  when the N requirements are high.When supply of N from soil is limited due to moisture stress as in rainfed conditions, foliar application of urea is beneficial.I request the colleagues to suggest any new innovations in use of urea N through foliage. Some times micronutrients and pesticides are also applied  along with 2% urea foliar application to save costs of applcation.Colleagues may point out any sensitive crops for urea foliar spray at some growth stages if any.Also what deviations are there in concentration and number of sprays in different crops.

We did trials with foliar spraying in rice at BRRI, Gazipur for four cropping season. We found that rice can be grown without significant yield reduction if two-third of N is applied as splits (10-15 DAT and 45-55 DAT) and instead of last topdressing we sprayed urea at 2.5% twice.

Johann very interesting question .  Foliar application of conventional urea many time leads to biuret toxicity in form of tip burn of leaves. In perennial crops , foliar spray of low-biuret urea is commonly practiced to induce flowering through De-novo arginine biosynthesis , leading to formation sperimine. Find enclosed one PDF for further reading .  

Dr.Biswas interesting information.For our understanding can  you give details of available (soil test)N in soil, total N spplied in 4 sprays,yield and N uptake by rice.This information helps us to understand the contribution of soil and foliar applied N to rice total N uptake at the yield level you achieved-

Many thanks you for your interesting contributions. I hope here comes still more light in this questions. JHUMER

 Look at this pictures of heavy maize leaf damages by a complex Zn, Urea, Phosphorus, Amalgerol-plantoil spray application on Maize  I saw in Hungary at August 2008.

Dr.Johann, interesting and practical problem illustration.I think if recommendation is research based it should not create problem. As I understand some farmers out their own innovation or influenced by some company or eextension workers go for such sprays. Still farmers are doing such practices which sometimes create problem for them.

 Dear Johann, i have seen all the photograph, its really too much damage. IN the presentation you mention that UREA+ZINC+ Amalgerol-oil+Phosphourus for foliar, One thing zinc and phosphorous is not compatible for foliar spray, it always shows same result when you apply together, if zinc is too necessary to apply with phosphorous, always use EDTA form of zinc,  and we are recommending surfactant with all foliar spray for equal distribution of nutrients on glossy leaves or any hairy leaves, but inspite of using the surfactant you use oil with spray, it stick on leaf and definitely cause damage to the leaf with higher concentration of solution on same place it restrict the material to disperse on the surface. Concentration also matter, urea can be sprayed successfully on maize at 4% max concentration.     

Foliar spray is never compete with soil applied nutrients, it's only addition with soil application to fulfill the requirement at certain stage when it is needed more, or to prevent the natural stress.   

We applied urea with insecticides and fungicides against Colorado beetle and late blight on potato. Urea can be tank mixed with a broad range of fungicides and insecticides. It is common treatment for ornamental plants as well.

Depending on the crop, urea is widely (foliar) applied with fulvic acid as chelating agent.  You can add micros and even phosphorus without burning. Albeit timely application is essential and treat as chelated material (for dosage, ambient temperature and spray equipment). Have been using for years on crops ranging from vegetables to grains, cacti (agave), pineapples, cucurbits, citrus and many more. Excellent results with higher yields and quality as long as the applications are timely at key phenological stages.

Pleaee Tell me how to make solution of urea foliar formula calculation for wheat in suitable and recommend dose of urea foliar %

Urea containing 46% N is usually applied to wheat crop especially under rainfed conditions at 1-2% urea concentration at tillering and heading stages.Some workers tried upto 4-5% urea concentrations to supply more N to crop.But one should be cautious with application of high urea concentrations with possible leaf injury/burning. To make 2 percent urea solution you have to mix 20 g urea in one litre water (2 g urea/100 ml). Foliar solutions are usually mixed with a surfactant like tween-80 at a concentration of 0.1 % v/v for improving leaf wetting and preventing droplets from immediate drying thereby prolonging the period of N absorption.0.1 percent means 1 ml per litre(v/v).