The Effects of Inorganic Nitrogen form and \(CO_2\) Concentration on Wheat Yield and Nutrient Accumulation and Distribution

Abstract

Inorganic N is available to plants from the soil as ammonium (\(NH^+_4\)) and nitrate (\(NO^-_3\)). We studied how wheat grown hydroponically to senescence in controlled environmental chambers is affected by N form (\(NH^+_4\) vs. \(NO^-_3\)) and \(CO_2\) concentration (“subambient,” “ambient,” and “elevated”) in terms of biomass, yield, and nutrient accumulation and partitioning. Wheat supplied with \(NH^+_4\) as a sole N source had the strongest response to \(CO_2\) concentration. Plants exposed to subambient and ambient \(CO_2\) concentrations typically had the greatest biomass and nutrient accumulation under both N forms. In general \(NH^+_4\)-supplied plants had higher concentrations of total N, P, K, S, Ca, Zn, Fe, and Cu, while \(NO^-_3\)-supplied plants had higher concentrations of Mg, B, Mn, and \(NO^-_3\) - N. \(NH^+_4\)-supplied plants contained amounts of phytate similar to \(NO^-_3\)-supplied plants but had higher bioavailable Zn, which could have consequences for human health. \(NH^+_4\)-supplied plants allocated more nutrients and biomass to aboveground tissues whereas \(NO^+_3\)-supplied plants allocated more nutrients to the roots. The two inorganic nitrogen forms influenced plant growth and nutrient status so distinctly that they should be treated as separate nutrients. Moreover, plant growth and nutrient status varied in a non-linear manner with atmospheric \(CO_2\) concentration.