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Abstract
The effects of 0.02, 0.06, 0.18, and 0.54 kg P/m3 incorporation as superphosphate (0-9-0) in peat–vermiculite and of NO3-N and NH4-H liquid feeds were investigated with tomato (Lycopersicon esculentum Mill. cv. Marglobe). Increasing P rate decreased shoot and root dry weights but increased total fruit fresh weight. NH4-N, relative to NO3-N nutrition, decreased shoot growth but had no effect on fruit yield. Decreased vegetative growth with increasing P rate and NH4-N nutrition was associated with decreased leaflet xylem pressure potential, increased transpiration rate, and increased leaf NH4-N concentration. Leaf P and medium water-soluble P concentrations increased with increasing P rate but were unaffected by N form. During time of fruit development, leaf P content decreased at the 2 lowest P rates but increased at higher P rates. Net P export from leaves ceased and luxury P consumption began between 0.06 and 0.18 kg P/m3.