During the 1st stage of growth higher Ca and N levels are required along with lower K levels to optimize the crops vegetative growth production. For this reason, a larger ratio of Ca(NO3)2:KNO3 = (80:20) is utilized.
During the 2nd Stage Ca+2 and N drop as K is brought up to promote more reproductive growth. This means less Calcium Nitrate is added during this stage however since N is also decreasing only a small increase in KNO3 occurs slightly affecting the Ca(NO3)2:KNO3 Ratio = (77.5:22.5). Once the maximum N is reached then larger amounts of K2SO4 must be utilized to bring up K levels the rest of the way.
During the 3rd/Final Stage Ca+2 and Mg+2 drop to bring up flower production while P is also lowered to maintain a balance b/t reproductive and vegetative states. The first reduction in KH2PO4 means more KNO3 can now be utilized in its place further decreasing the Ca(NO3)2:KNO3 Ratio to (73:27).
Crops require 16 elements to survive. C, O, H are captured from the air, therefore 13 are essential nutrients that must be obtained from the water.