Nitrogen deficiency (N)
In case of nitrogen deficiency, olive leaves will frequently be smaller and deformed. They will also show chloroses in the form of large-scale yellowing. Older leaves may exhibit a reddish colouration. Internode shortening is also possible.
In order to prevent nitrogen deficiency, it is advisable to apply nitrogen in a readily absorbable form (ammonium nitrate).
Another option is foliar application, or, in serious cases, fertigation. This method will allow plants to immediately absorb the nutrient.