Effects of nitrapyrin and nitrogen form on tomato lycopersicon esculentum cultivar marglobe growth water relations and ion composition

Pill, W.G.; Sparks, D.L.

Journal of the American Society for Horticultural Science 107(3): 487-492


ISSN/ISBN: 0003-1062
Accession: 005316251

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Nitrapyrin (NI) at 10 ppm, compared to water control, added to a soil-sand-peat medium decreased shoot growth of tomatoes (L. esculentum Mill. cv. Marglobe) grown with NO3-N nutrition but had no effect on growth with NH4-N nutrition. While plant water stress was decreased by NI compared to the control with NO3-N nutrition, the toxic effect of increased uncombined NH4 concentration in the shoots may have caused the growth reduction. Denitrification suppression by NI with NO3-N nutrition was evidenced by increased media and shoot NO3 concentrations. Nitrification suppression by NI with NH4-N nutrition was evidenced by increased media and shoot NH4 concentrations. Nitrapyrin, irrespective of N form, decreased shoot Ca concentration, increased shoot K and uncombined NH4 concentrations, and had on effect on shoot Mg concentration. Plant water stress was decreased by NI with both N forms at the 3rd and 5th wk after final transplanting. While NI decreased the differential effect of N form on transpiration rate and leaf diffusive resistance (RL), in NI's absence, NH4-N nutrition decreased transpiration and increased RL relative to NO3-N. Decreased shoot growth with NH4-N relative to NO3-N nutrition, both in the presence and absence of NI, was associated with increases in plant water stress, root hydraulic resistance, and shoot uncombined NH4 concentration, but a decrease in shoot Ca concentration.