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Growth, Nutrient Status, and Chlorophyll Meter Readings in Wheat as Affected by Nitrogen and Manganese

Abstract Mineral nutrition of wheat (Triticum aestivum L.) in highly calcareous soils low in available nitrogen (N) and manganese (Mn) requires further investigations. The purpose of this experiment was to determine the effect of N and Mn on the growth, nutrient concentration and uptake, and chlorophyll meter readings (CMR) in wheat grown in greenhouse conditions. The experiment was conducted on a highly calcareous soil (fine-loamy, carbonatic, thermic, Typic Calcixerepts) relatively low in available N and Mn. Treatments consisted of a factorial arrangement of five N rates (0, 50, 100, 200, and 400 mg kg−1 as NH4NO3) and three Mn levels (0, 15, and 30 mg kg−1 as MnSO4) in a completely randomized design with four replications. Plants were grown for 60 d and hand-held chlorophyll meter (Minolta SPAD-502) readings were used to evaluate dry matter (DMY) and N, Mn, iron (Fe), zinc (Zn), and copper (Cu) concentration of wheat in aerial parts. Applied N increased DMY and concentration and uptake of N, Mn, Fe, Zn, and Cu, and Mn:Fe ratios. A significant correlation was obtained between DMY and applied N (R2 = 0.75). Manganese had no significant effect on DMY, N, Zn, Cu concentration and uptake, and Fe uptake. However, Mn rate increased Mn concentration and uptake and Mn:Fe ratio and reduced Fe concentration. Interaction of N × Mn did not affect DMY, concentration, or uptake of any of the nutrients. The CMR increased significantly with N rate but was not influenced by Mn addition. Highly significant correlations were observed between CMR and DMY (R2 = 0.84), and the concentrations of N (R2 = 0.97), Mn (R2 = 0.70), Fe (R2 = 0.73), Zn (R2 = 0.93), and Cu (R2 = 0.90). It is concluded that portable chlorophyll meter is a quick, reliable, and nondestructive tool for assessing DMY and nutrients affecting leaf greenness in wheat. However, further investigation in field conditions is recommended.