Growth and Nutrients Imbalance in Silage Corn as Affected by Copper and Manganese Application in a Calcareous Soil

Copper (Cu) and manganese (Mn) deficiency have been reported in soils of Iran. These nutrient deficiencies could be due to high soil pH and nutrients imbalance between Cu and Mn and other nutrients including Ca, Mg, Fe, and Zn in calcareous soils. In order to study the effect of Cu, Mn, and Cu × Mn interaction on growth and nutrients imbalance in silage corn (Zea mays L.), a factorial experiment of 4 × 4 was carried out in a completely randomized design with three replicates in a calcareous soil (fine, mixed (calcareous), mesic Typic Calcixerepts) under greenhouse conditions. Treatments consisted of four levels of Cu (0, 5, 10, and 20 mg kg-1 from CuSO4. 5H2O), and four levels of Mn (0, 10, 20, and 40 mg kg-1 from MnSO4. 4H2O) with three replicates. Results indicated that Mn significantly increased corn shoot dry matter yield (SDMY), but application of 20 mg Cu significantly decreased SDMY. Other levels of Cu had no significant effect on plant growth. Reduction of SDMY might be due to the antagonistic effect of Cu on Fe uptake and imbalance of Cu:Mn, Cu:Fe, and Cu:(Mn+Fe+Zn). Application of Cu increased Cu concentration and uptake in plant aerial part but had no effect on concentration and uptake of Mn. Addition of Mn decreased concentration of Cu but increased the plant uptake. Manganese decreased concentration of Fe but increased its uptake. Addition of Cu and Mn had no effect on plant Zn concentration, but Mn increased Zn uptake. Shoot: root ratio was not affected by Mn or Cu addition. The maximum SDMY was obtained by application of 5 or 10 mg Cu kg-1 and 20 or 40 mg Mn kg-1. The sufficiency range for Cu was 6 to 7 µg g-1 and 50 to 55 µg g-1 dry matter for Mn. The results of this study need to be verified under field conditions before making any fertilizer recommendation.