Evaluation of Phenological Cycles and Thermal Time of Apple Crop Growing at Different Altitudinal Gradients in North Western Himalayas

Abstract

A field study was conducted in 2015 and 2016 to evaluate the phenological cycles and thermal time of apple crop of economic importance growing at different climate represented by varied altitudinal gradients in Himachal Pradesh, India. The experiment was laid out in Randomized Block Design with three altitudinal gradients at 1000-1000 m amsl (gradient I at Bajaura), at 1150-1250 m amsl (gradient I at Seobagh), at 1500-1600m amsl (gradient I at Rohru), Bajaura (altitudinal gradient I at 1000-1100 m amsl), Seobagh (altitudinal gradient II at 1150-1250 m amsl) and Rohru (altitudinal gradient III at 1500-1600 m amsl) and five commercial cultivars as two factors.The air temperature at mid and higher altitudinal gradients ranged from 7.9 to 17.1 °C and 7.3 and 15.3 °C, which was 1.0 to 1.9 °C and 2.2 to 3.4 °C less than the lower altitudinal gradient, respectively. The dormancy break at mid gradient was advanced by 1-3 and 3-6 days in attainment of silver tip stage at higher gradient. All phenophases were significant and negatively correlated to the average air temperature from January to April indicating that higher temperature after the winter rest of plants accelerated the developmental processes and finally led to an advanced timing of spring events. The GDD had a negative correlation with the occurrence of the different phenological stages of apple crop indicating that with increased accumulation of heat the attainment of phenological stages will be advanced. The warming in the early spring (February–April) by 2-4 °C at lower elevation caused an advancementof the beginning of phenophases by 7-13 days.