Tomato growth and nutrient uptake patterns as influenced by nitrogen form and light intensity1

Tomato plants were grown in sand culture with NH4 or NO3 forms of N and at two levels of light. Plants were harvested at 0, 5, 9, or 12 days after starting treatments. NH4‐N nutrition reduced growth, suppressed K, Ca, and Mg accumulation in shoot, increased P and N content and markedly reduced K, Ca, and Mg uptake per unit of root surface. Reduced light level decreased the toxic effects of NH4 and markedly decreased NH4 accumulation in shoots.