Nitrogen stress effects on growth and nitrogen accumulation by field-grown tomato

There are few growth studies evaluating within-season effects of N on vegetative growth and N accumulation of tomato (Lycopersicon esculentum Mill.). Growth analysis of field-grown tomato for a number of Florida locations and management systems is presented here. Severe N stress resulted in fewer and smaller, but thicker, leaves. With increasing N, average leaf area index (LAI) increased from approximate to 0.75 to approximate to 3, but radiation use efficiency (RUE) typically increased less then 30%. Lower RUE under N-limited conditions reflected a decrease in N concentration of the most recently matured leaves from 40 mg g(-1) to as little as 15 mg g(-1). Over the life of well-fertilized crops, leaf N concentrations dropped from 55 to 65 mg g(-1) during initial growth to 20 to 35 mg g(-1) at final harvest. Corresponding N concentrations for fruit and for stems were 30 to 35 mg g(-1) and 15 to 25 mg g-X Severe N stress affected leaf and stem N concentrations most drastically, whereas N in fruits was less variable. With lower N supply (N < 180 kg ha(-1)) under careful management, nitrogen use efficiency (NUE) for field-grown tomato was approximate to 0.4 Mg fresh fruit (kg N)(-1) and average crop N accumulation increased from 37 to 210 kg N ha(-1) as N fertilization increased from 0 to 333 kg N ha(-1). As a fraction of the fertilizer N applied N fertilizer recovery ranged from 0.36 to 0.74 and 0.61 to 0.96 for drip-irrigated and subirrigated crops, respectively.