questions: asking about control of nitrogen dificiency in cucumber 
 answers: advised him that the symptoms are matching with nitrogen deficiency like both vegetative growth and fruit production are severely restricted plants appear pale and spindly.  new leaves are small but remain green, whereas the oldest leaves turn yellow and die.  the yellowing spreads up the shoot to younger leaves.  yield is reduced and fruit are pale, short and thick.
so, apply urea @ 20g/lit as foliar spray at 15 days interval or npk @ 10g/lit of water