Corn Responses to Post‐tasseling Nitrogen Deprivation and to Various Ammonium/Nitrate Ratios

Abstract

AbstractCorn (Zea mays L.) takes up more than half of its total N after tasseling. An experiment was conducted to determine how the availability of N and the N form, NH4 or NO3, during the post‐tasseling period affect corn plant growth, ear development, and nutrient composition. In this experiment, corn hybrid ‘Pioneer 3343’ plants were grown hydroponically in pots outdoors with 50:50 NH4:NO3 up to the emergence of tassels and then the plants were either deprived of N or changed to various ratios of NH4:NO3 nutrition and grown to maturity. Nitrogen deprivation reduced both vegetative (stalk and leaf) and reproductive (cob, total kernel, and individual kernel) dry matter accumulation. Continuous supply of 50:50 ratio of NH4:NO3 produced greater vegetative dry matter than changing to either higher or lower ratios of NH4:NO3. The ratio of NH4:NO3 did not affect the ear dry matter production. Nitrogen deprivation decreased both leaf and kernel N concentration. While 50:50 NH4:NO3 ratio increased the leaf N concentration, all NH4 increased the kernel N concentration compared to other ratios. Nitrogen deprivation also reduced the concentrations of Mg, Fe, Mn, Zn, and B in the leaves but had no effect on the kernel nutrient composition. The cation and anion concentrations in the leaves and kernels were not according to the NH4 and NO3 effects (viz., uptake of cations greater and anions lower with NH4 than with NO3 nutrition), which were previously observed before tasseling. This difference may be due to a change in the uptake capacity for these nutrients after tasseling.