Calcium efficiency among tomato strains depends on nitrogen regimes 1

Two Ca‐efficient and 3 Ca‐inefficient tomato strains were grown for 18 days in nutrient solutions with NH₄‐N:NO₃‐N ratios (%) of 0:100, 50:50, or 90:10 and with 40 mg of total Ca⁺⁺. When NH₄‐N nutrition was used, efficient strains exhibited Ca‐deficiency symptoms sooner or produced less dry matter than inefficient strains. The greatest reductions in dry weight production occurred between 50 and 90% NH₄‐N nutrition. The greatest reduction in solution pH and in % of Ca in plant tissues occurred between 0 and 50% NH₄‐N nutrition. Ratings of Ca efficiency varied according to the proportion of NH₄‐N in the nutrient solutions.