Mycorrhizal Effectiveness on Wheat Nutrient Acquisition in an Acidic Soil from Southern Chile as Affected by Nitrogen Sources

ABSTRACT

Acidity, aluminium (Al) and manganese (Mn) phytotoxicity, and low levels of available phosphorus (P) are the main constraints for plants growing in Andisols from southern Chile. This study was carried out to evaluate the effect of arbuscular mycorrhizal (AM) fungus inoculation and two nitrogen (N)-sources on the growth and mineral uptake of wheat (Triticum aestivum L.) plants grown in an acidic Andisol at 120 and 150 days after sowing (DAS). The plants were grown in pots under greenhouse conditions with or without inoculation with the AM fungus Glomus etunicatum CH110 (Morton and Bentivenga) and fertilized with N-ammonium (NH₄ ⁺) or N-nitrate (NO₃ ⁻). The biomass production was not affected for any treatment used, but the inoculation with G. etunicatum increased the shoot contents and specific absorption rate (SAR) of P and zinc (Zn) at 120 and 150 DAS, especially when N-NH₄ ⁺ was used. On the other hand, the use of N-NO₃ ⁻ increased the N (at 120 DAS), potassium (K) (120 and 150 DAS), and copper (Cu) (120 DAS) shoot content, reduced the Al shoot content and Mn SAR (both at 120 DAS). The combined use of G. etunicatum inoculation and N-NO₃ ⁻ use decreased significantly (P < 0.001) the Mn shoot content and the Al SAR at 150 DAS. The results suggest the selection of NO₃ ⁻ as N-source to address practical and ecological fertilization management, which is important for acidic volcanic soils from southern Chile, with a natural tendency to produce Mn and Al phytotoxicity.

Keywords:

• arbuscular mycorrhiza
• N fertilization
• specific absorption rate
• acidic volcanic soils

ACKNOWLEDGMENTS

This work was supported by Fondecyt, grant 1990756, from Comisión Nacional Científica y Tecnológica, Chile. The authors also acknowledge financial support given to R. Azcón for travel and expenses while staying in Chile through Fondecyt CI grant 7990086.

Notes

∗ P < 0.05,

∗∗ P < 0.01,

∗∗∗P < 0.001, ns = no significant differences.

^a Interaction between the factors AM inoculation and N source.

^b Element content = amount in plant shoot (two plants).

^c μ g of element per mg of root dry matter.

∗ For each crop stage, means followed by the same letter in a column are not significantly different using orthogonal contrasts test (P < 0.05, n = 4).

∗For each crop stage, means followed by the same letter are not significantly different using t-student test (P < 0.05, n = 4).