Effects of soil water regime and nitrogen form on blossom end rot yield water relations and elemental composition of tomato lycopersicon esculentum

Pill, W.G.; Lambeth, V.N.

Journal of the American Society for Horticultural Science 105(5): 730-734


ISSN/ISBN: 0003-1062
Accession: 005326086

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Decreasing soil water potential (minima of -0.3, -2.0 and -6.0 bars) reduced fruit number, set and mean and total fruit weight of tomato (L. esculentum Mill). Under the 2 wettest soil water regimes, NH4-N compared to NO3-N fertilization reduced total and mean fruit weights but increased fruit number whereas no differences in these variables were found between N-forms under the driest regime. Incidence and severity of blossom-end rot (BER) were increased by NH4 nutrition and by decreasing soil water potential (SWP). Decreasing SWP either had no effect or increased leaf Ca, Mg and K concentrations but decreased fruit concentration of these ions. At any soil water regime, NH4 fertilization decreased leaf Ca and Mg concentration but generally increased leaf K and fruit Ca, Mg and K concentrations. While BER incidence and severity apparently were not related to fruit Ca, Mg and K concentrations, the disorder was associated with increased stylar to calyx fruit-half concentration ratios of these ions. Basal (pre-dawn) leaf xylem pressure potential (.psi.p) was unaffected by N nutrition but was greater (less negative) under the wettest regime. Compared to plants supplied with NO3-N whose minimal and mean light-saturation .psi.p values decreased SWP, plants given NH4-N reached a constant .psi.p level regardless of soil water regime. Since leaf diffusive resistance (RL) values increased with decreasing SWP, but were unaffected by N form, the lower transpiration and transpiration rates under NH4-N might be explained by increased non-leaf resistances to water flux and/or by reduced soil-plant water potential gradients.