Ammmonium and Nitrate Uptake by Corn (Zea mays L.) as Influenced by Nitrogen Concentration and NH+4 /NO‐3 Ratio¹

Abstract

Corn (Zea mays L.) absorbs both ammonium and nitrate forms of N. Both are usually present in the soil and some control of their proportions can be obtained by controlling nitrification. Little is known about the relative rates of absorption of these ions or their effect on plant growth rate when both are present. We investigated the effects of NH4+ and NO3− on corn by growing 13‐day‐old corn seedlings for an additional 5 days in 25 nutrient solutions consisting of 5 N concentrations (15.9, 67.1, 303, 1507, and 6015 μM) at each of 5 NH4+/NO3− ratios (8.40, 2.46, 1.05, 0.49, and 0.17). Solution NH4+, NO3−, and pH were monitored and variations kept to a minimum. Uptake rates of NH4+ and NO3− were estimated separately from solution analysis. Maximum dry matter accumulated with an N concentration of 67 μM. Maximum N uptake occurred for the combination of 303 μM N and a NH4+/NO3− ratio of 2.46. Shoot/root ratio increased significantly with increased N concentration, but was unaffected by NH4+/NO3− ratio. Above 67 μM N, the NH4+/NO3− ratio of absorbed N tended toward 1.0 as compared with the ratio in solution. There was no significant difference between NH4+ and NO3− in their relative rates of absorption. Increasing the concentration of NH4+ reduced the NO3− uptake rate and increasing the NO3− concentration reduced the NH4+ uptake rate. Each mutually influenced the absorption of the complementary nitrogen form to the same degree.

Effects of fertilisers on vegetable production 1. Yield of spinach and beetroot as affected by rates and forms of nitrogenous fertilisers

“…Root yields were reduced at all N application rates. Ammonium toxicity has been shown to affect root growth more than top growth (Warncke & Barber 1973;Haynes & Goh 1977).…”

Combined effects of nitrogen to phosphorus and nitrate to ammonia ratios on cyanobacterial metabolite concentrations in eutrophic Midwestern USA reservoirs

“…The ratio of oxidized nitrogen (nitrate and nitrite) to reduced nitrogen (ammonia and ammonium) has important implications for the growth rate, mineral composition, and production of carbon-rich organic compounds in photosynthetic organisms (Warncke and Barber 1973, Johnson et al 1984, Praveen et al 2011. For example, the nitrate to ammonium ratio (NO 3 :NH 4 ) plays a role in the formation of oxalic acid in terrestrial plants, with decreasing NO 3 :NH 4 ratios causing decreases in oxalic acid concentrations (Palaniswamy et al 2004, Zhang et al 2005, Fontana et al 2006.…”

Simultaneous Measurement of NH4+ Absorption and N2 Fixation by Glycine max L.

“…It is generally acknowledged that the presence of N03 does not affect the uptake of NH4' (14) ( Table IV), although increased concentrations of NO3 have been observed to reduce NH4' absorption (10,22). One would expect each N ion to influence the other, since both are forms of N and are metabolized into amino acids.…”