The influence of graded nitrogen levels and accumulated growing degree days on the tuber yield of the heat-resistant/tolerant potato variety Kufri Surya

The effect of varying doses of nitrogen (0, 75, 150, 225, and 300 kg ha ^− 1 ) on the tuber yield and economic outcomes of the potato variety Kufri Surya was investigated at the All India Coordinated Research Project on Potato, Odisha University of Agriculture & Technology, Bhubaneswar, Odisha, India, during the winter seasons over a five-year period from 2013-14 to 2017-18. The experimental site featured sandy-loam soil with a pH of 5.2 and an electrical conductivity (EC) of 0.297 dSm ^− 1 . The experiment utilized a randomized block design with four replications. The crop was planted in November and harvested in January/February, 75 days post-planting. Phosphorus (P ₂ O ₅ ) and potassium (K ₂ O) doses were kept consistent across all treatments. Cumulative growing degree days (GDD) were calculated by summing daily mean temperatures above the base temperature, expressed in degree days. Among the different nitrogen treatments, 225 kg N ha ^− 1 yielded the highest mean tuber yield of 21.21 t ha ^− 1 , along with net returns of Rs. 88,350 ha ^− 1 and a benefit-cost (B:C) ratio of 1.71. The 225 kg N ha ^− 1 dose produced significantly higher tuber yields compared to the 150 kg N ha ^− 1 dose recommended for Odisha. Although applying 300 kg N ha ^− 1 resulted in higher yields than 225 kg N ha ^− 1 during the initial two years, this trend did not continue. The mean yield with 300 kg N ha ^− 1 was significantly lower than with 225 kg N ha ^− 1 . There was a gradual increase in tuber yield from 0 kg N ha ^− 1 to 75 kg, 150 kg, and 225 kg ha ^− 1 . The results clearly indicate the necessity of increasing the recommended nitrogen dose from 150 kg ha ^− 1 to 225 kg ha ^− 1 for Odisha, particularly in sandy-loam soils. It was observed that the combination of lower GDD and lower bright sunshine hours (BSH) of 397 hours led to the lowest helio-thermal units (HTU) of 3888.9, resulting in the highest tuber yield with maximum heat use efficiency (HUE) of 371.3g°C days ^− 1 hrs ^− 1 and helio-thermal use efficiency (HTUE) of 6.0.