Rate and timing of nitrogen fertilization of Russet Burbank potato: Yield and processing quality

Split fertilizer N application is thought to improve fertilizer N use efficiency of potato, primarily by reducing NO3 leaching losses. This study evaluated the effects of the rate and timing of N fertilization on yield and processing quality of Russet Burbank potato under rain-fed production. Trials conducted in 1999-2001 included different fertilizer N rates (0-160 kg N ha(-1) in 1999 and 0-200 kg N ha(-1) in 2000 and 2001) applied either at planting according to normal grower practice, or at hilling, the latest time that granular fertilizer can practically be applied. Tuber total and marketable yield, size distribution, specific gravity, fry colour and tuber concentrations of NO3, sucrose and glucose were measured. Increasing rates of N fertilization increased tuber yield and tuber size, increased tuber NO3 concentration and decreased tuber specific gravity, but had little effect on tuber sugar concentrations or fry colour. Season-to-season variations in total tuber yield responses to N fertilization rate were attributed primarily to variation in soil N supply. Timing of N application had little effect on tuber yield, size distribution or processing quality under adequate soil moisture conditions. However, under dry soil conditions, split N application reduced tuber yield and tuber size.