Effects of Nitrogen Form and Level on Ion Concentrations, Water Stress, and Blossom-end Rot Incidence in Tomato1

Abstract

Abstract Ammonium nutrition, in comparison to NO3–N nutrition, of tomato in sand culture reduced shoot growth, total and mean fruit weight, fruit number, leaf xylem pressure potential, leaf CA, Mg, and NO3 concentration, and normal fruit Ca, Mg, K, and NO3 concentration. Leaf diffusive resistance, leaf NH4 concentration, and blossom-end rot incidence were increased by NH4–N nutrition. Increasing substrate NO3 level increased shoot growth, fruit number per plant, and fruit NO3 concentration. Increasing substrate NH4 level increased leaf diffusive resistance, and leaf xylem pressure potential, but had no effect on shoot growth. Under both N forms, increasing N level did not affect fruit yield or normal fruit Ca, K, or P concentration, but decreased leaf Ca, Mg, and P concentration, and increased normal fruit Mg. Blossom-end rot occurred only under NH4–N nutrition. Affected fruit had lower Ca, Mg, NO3, and NH4 concentration and higher fruit K/Ca ratio. Fruit condition exerted no effect on fruit P or K concentration.