questions: asking about the recommended fertilizer dose for lemon tree at the age of 4 years. 
 answers: suggested to apply recommended fertilizer dose like-urea@1320 gram/plant,ssp@2500 gram/plant,mop@968 gram/plant,fym@20 kilogram/plant.fertilizer should be applied in  a trench in two equal split doses twice in a year in the month of march/april and october/november.