INTERACTION OF POTASSIUM WITH THE FORM AND AMOUNT OF NITROGEN NUTRITION ON GROWTH AND NITROGEN UPTAKE OF MAIZE

Although a mixture of NO3-N and NH4-N improves the growth of maize plants over that with NO3-N or NH4-N alone, the ratio required for maximum growth remains unclear. Maize hybrid B73 x MoI7 was grown in vermiculite at 25-degrees-C in a controlled climate room with a 16-h photoperiod at 280-mu-E/sec/m2 to evaluate effects of the form and amount of N, and the N/K ratio on the growth of seedlings. The proportion of NH4-N in the mixture required for maximum growth varied according to the total amount of N in the medium. Under low N conditions, seedlings grew faster with a higher proportion of N in the NH4 form while a greater proportion of NO3-N was advantageous at high N conditions. When seedlings were grown under NH4-N as the sole N source, high K levels promoted root growth, and dry matter and N accumulation in the shoot.