Growth and composition of tomato as affected by source of nitrogen and biocides

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Abstract
Tomato (Lvcopersicon esculentum Mill.) was grown in soil culture in a greenhouse. Potassium nitrate, calcium nitrate, and urea as N sources were compared using biocides (nitrapymn, captan, treflan, and DDT) and an untreated control. The largest shoot growth and fruit yields were obtained with plants fertilized with potassium nitrate. Potassium deficiency, manifested by leaf and stem necrosis and low levels of K in these tissues, appeared to be a limiting factor for the plants receiving urea or calcium nitrate. The depression of leaf and stem K by NH4 + or Ca++ was associated with the antagonism of these ions on K+ absorption. The biocides limited plant growth especially with urea and potassium nitrate. Depression of K, Ca, or Mg concentrations in the plants were effects associated with the biocides and their interactions with N sources.