Effect of Magnesium Deficiency on Pepper Growth Parameters: Implications for Determination of Magnesium‐Critical Value

In order to improve determinations of nutrient critical levels using growth response curves, a detailed study of magnesium (Mg) deficiency on pepper (Capsicum annuum L.) biomass allocation was performed. For each growth parameter, data were fitted using the modified Mitscherlich's model and Mg‐critical level was calculated. Under Mg‐deficiency, pepper plants showed a decrease in their relative growth rate (RGR), total dry weight (DW), stem and root mass fractions (SMF and RMF), total leaf area, specific leaf area (SLA), and unit leaf rate (ULR), whereas leaf mass fraction (LMF) and shoot to root ratio increased. Growth response coefficient (GRC) analysis indicated that the decrease in RGR was mainly due to a decrease in ULR. When the interval time between two harvests was ≥10 days, determination of Mg‐critical level (x c ) using the modified Mitscherlich's model showed that the best growth parameter for early detection of Mg‐deficiency in pepper plants was total DW (x c ≈ 0.21%), whereas other parameters underestimated Mg‐critical level.