Urea of foliar spray should not contain biuret more than

Answer: Option B

Urea of foliar spray should not contain biuret more than 1.5%. Fertilizer-grade urea contains the impurity Biuret which is toxic to the plant, especially when applied as a leaf dressing. Thus Biuret more than 1.5% can damage the root of the plant and also useful bacteria and chock the capillary of the root cell, Nitrogen carrying capacity will be reduced.