$A$ farmer adds/supplies $Na, Ca, Mg$ and $Fe$ regularly to his field and yet he observes that the plants show deficiency of $Ca, Mg$ and $Fe$. Give a valid reason and suggest a way to help the farmer improve the growth of plants.

(N/A) $\Rightarrow$ The primary reason for this observation is the phenomenon of nutrient antagonism. When one mineral ion is present in excess,it can inhibit the uptake or translocation of other mineral ions.
$\Rightarrow$ In this case,the excessive addition of $Na$ ions likely interferes with the absorption and utilization of $Ca^{+2}$,$Mg^{+2}$,and $Fe^{+3}$ ions by the plant roots.
$\Rightarrow$ Mineral ions compete for the same binding sites on transport proteins in the cell membrane. An imbalance in the concentration of these ions leads to competitive inhibition.
$\Rightarrow$ To improve plant growth,the farmer should perform a soil test to determine the exact nutrient requirements and avoid the excessive use of $Na$. He should apply a balanced fertilizer regimen that provides essential nutrients in appropriate,non-competitive ratios to ensure optimal uptake.