THE EFFECT OF AN NH4+-ENHANCED NITROGEN-SOURCE ON THE GROWTH AND YIELD OF HYDROPONICALLY GROWN MAIZE (ZEA-MAYS L)

Increased above-ground dry matter and grain yields were found for two hydroponically grown maize hybrids (Pioneer-3925 and Pioneer-3949) when plants were supplied with an NH4+-enhanced nutrient solution (31 percent of total N) compared with a control (4 percent of total N as NH4+). The major difference in yield developed between silking and 2 weeks post-silking and silking and 4 weeks post-silking for the P-3925 and P-3949 respectively. The reduced nitrogen content of the stover (leaves plus stalk) was consistently higher on the NH4+-enhanced nutrient solution. The decreased production of the control treatment may have resulted from a reduced photsynthetic capacity.