Aluminum–Nitrogen Interactions in the Soil–Plant System

Abstract

Aluminum (Al) is the most abundant metal in the Earth’s crust and is not an essential element for plant growth. In contrast, nitrogen (N) is the most important mineral element for plant growth, but this non-metal is often present at low levels in soils, and plants are often N deficient. Aluminum toxicity is dominant in acid soils, and so plants growing in acid soils have to overcome both Al toxicity and N limitation. Because of low N-use efficiency, large amounts of N fertilizers are applied to crop fields to achieve high yields, leading to soil acidification and potential Al toxicity. Aluminum lowers plant N uptake and N-use efficiency because Al inhibits root growth. Although numerous studies have investigated the interactions between Al and N, a complete review of these studies was lacking. This review describes: (1) the link between plant Al tolerance and ammonium/nitrate (NH4+/NO3-) preference; (2) the effects of NH4+/NO3- and pH on Al toxicity; (3) the effects of Al on soil N transformations; and (4) the effects of Al on NH4+/NO3- uptake and assimilation by plants. Acid soils are characterized chemically by a relatively high ratio of NH4+ to NO3- and high concentrations of toxic Al. Aluminum-tolerant plants generally prefer NH4+ as an N source, while Al-sensitive plants prefer NO3-. Compared with NO3-, NH4+ increases the solubilization of toxic Al into soil solutions, but NH4+ generally alleviates Al phytotoxicity under solution culture because the protons from NH4+ compete with Al3+ for adsorption sites on the root surface. Plant NO3- uptake and nitrate reductase activity are both inhibited by Al, while plant NH4+ uptake is inhibited to a smaller degree than NO3-. Together, the results of numerous studies indicate that there is a synergistic interaction between plant Al tolerance and NH4+ nutrition. This has important implications for the adaptation of plants to acid soils that are dominated chemically by toxic Al as well as NH4+. Finally, we discuss how this knowledge can be used to increase plant Al tolerance and N-use efficiency in acid soils.

Fertilizer Potential of Struvite as Affected by Nitrogen Form in the Rhizosphere

“…However, in the present study, PCaCl2 concentration in the 0P control was as high as those in the TSP or struvite treatments, which suggests that root-induced acidification increased solubility of legacy soil P, likely due to desorption of (hydr)oxide surfaces and weathering [27]. As shown in Figure 4, the pH decrease in the NH4-supplied rhizospheres led to an increase of soluble Al concentration which is consistent with previous findings (e.g., review by Zhao et al [45]). As reported by other researches [27,46], the release of Al into the soil solution may promote the precipitation of variscite, AlPO4.2H2O, especially in P-fertilized agricultural soils.…”

Aluminum toxicity reduces the nutritional efficiency of macronutrients and micronutrients in sugarcane seedlings

“…It can be explained by the interference of Al in the metabolism of N, such as in the translocation and reduction of nitrate in the roots (Gomes et al, 1985) to decrease N in the shoot and hence limit dry matter production by plants. Another fact related to the low N use efficiency is related to changes in the root growth because Al inhibits it (Zhao;Shen 2018). BORGES, C. E. et al Calcium uptake and translocation efficiencies ( Figure 6D and E) increased linearly as Al concentrations increased in the nutrient solution.…”

“…In general, for the micronutrient Zn and Cu, the absorption efficiency was reduced by the lower accumulation of these nutrients in the presence of Al. It is known that the greatest effects caused by the toxicity of Al is the reduction in the absorption of nutrients, mainly cations divalent, in this case, aluminum ions can bind to the cell surface and form a positively charged region, thereby inhibiting the adsorption of positively charged cations on the cell surface (Zhao;Shen, 2018), however for this cane genotype, this was not clear for the other divalent cations (Ca, Mg, Fe and Mn).…”

High Aluminum Drives Different Rhizobacterial Communities Between Aluminum-Tolerant and Aluminum-Sensitive Wild Soybean

“…These results provided more evidence on NH 4 + -N mitigating the toxicity of Al to plants (Zhao and Shen, 2018). An increase in NH 4 + -N decreases pH, thereby increasing the content of Al 3+ and H + (Zhao and Shen, 2018). However, Al-T plants may be able to take up more H + and suppress Al 3+ to enter the plant roots, consequently reducing Al phytotoxicity (Zhao et al, 2009(Zhao et al, , 2014.…”