Nitrogen Application Frequency for Drip-irrigated Tomatoes

Studies were conducted to determine the effect of N application frequency through drip irrigation on soil NO 3 -N movement in the bed profile and on yield and N uptake by tomato plants (Lycopersicon esculentum Mill. `Sunny') at two locations. Increasing N application frequency resulted in increased yields at Clayton, N. C., but not at Charleston, S.C. The number of fruit produced was not affected by N treatment at either location, but fruit size increased with increasing N application frequency at Clayton. Foliage N concentration decreased seasonally, but neither foliage N concentration nor total N content of the above-ground portion of the plants was affected by N application frequency. Regardless of N application frequency, NO 3 -N concentrations within the raised bed decreased with time due to plant uptake and leaching. Nitrogen levels declined most rapidly in the area closest to the drip tube.