Let's try to understand what the plant is trying to tell us.
NITROGEN -
• yellowing of the older leaves of the plant
• growth of the plant stops
• leaves start to fall
• dropping off of flowers & fruits
• drying off of new shoots
PHOSPHORUS -
• leaves will turn a darker green or purple
• delay in flowering
• delay in fruiting
• the root system of the plant weakens
POTASSIUM -
• burning of the leaves at its edges
• the branches of the plant are brittle, not strong
• the plant's immune system weakens and its ability to naturally ward off pests or diseases reduces
SULFUR -
• new leaves turning yellow
• the plant starts looking pale, sick, unhealthy, yellow or lighter in shade than normal
ZINC -
• the leaves shrink in size comparitively
• shrinking of the nodes and internodes
CALCIUM -
• curling of the leaves
• black or brown spots on the bottom side of the fruit especially in tomatoes also known as blossom end rot
COPPER -
• wilting of leaves
• drying out of new branches
BORON -
• deformation of the actual shape of the fruit or flowers
• lack of growth with regards to root formation
MOLYBDENUM -
• lack of proper use of the nitrogen in the soil
• yellowing of the leaves
SILICON -
• lack of strength in the branches of the plant
• plant is prone to frequent pest attacks or diseases