Iron deficiency starts when it is

Solution (By Examveda Team)

Iron deficiency starts when it is < 55 ppm.
Iron (Fe) deficiency chlorosis is a major nutritional disorder for crops growing in calcareous soils and causes decreases in vegetative growth as well as marked yield and quality losses.
Soil iron concentration is high, but can become unavailable for absorption if soil pH is higher than 6.5.