Precising nitrogen requirement of table potato (Solanum tuberosum) cultivars for different growth periods

A field experiment was conducted for 3 consecutive seasons (20042007) at Modipuram to optimize the growth period-specific N requirements of table potato cultivars Kufri Pukhraj and Kufri Anand in sandy loam soils. Growth, yield and economic parameters of both the genotypes were evaluated for their response to 4 N levels (0, 90, 180 and 270 kg/ha) and 2 growth periods (75 and 110 days). The crop-growth traits and tuber number were not influenced due to harvest stages; however, tuber yield was 31.3% higher with extended duration (110 days). N ap- plication had favourable effect on growth parameters, but showed quadratic response to marketable and total tuber number/ha. Likewise, it showed steady increase in marketable and total tuber yields. Agronomic N-use efficiency (118.666.0 kg tubers/kg N applied) decreased linearly with increase in N levels. Kufri Anand recorded better growth than Kufri Pukhraj, but tuber number and yield as well as economic variables were statistically similar in both the cultivars. Net income and benefit : cost (B: C) ratio indicated that both the cultivars should be fertilized with 270 kg N/ha when harvested at 110 days, but 180 kg N/ha is sufficient when harvested at 75 days.