Phenology, growth and yield of Kangra tea in relation to agrometeorological indices

Abstract In this study, phenology, growth, yield characteristics, and agrometeorological indices—Growing Degree Days (GDD), Heliothermal Units (HTU), Photothermal Units (PTU), and Hygrothermal Units (HYTU)—in Kangra tea ( Camellia sinensis L.) were examined. Plant height, leaf count, leaf area index (LAI), and dry matter accumulation were all examined using data gathered during eight phenophases (P1–P8). During early phenophases, GDD had a positive impact on vegetative growth. The strongest positive correlations were found for LAI during P3–P4 ( r = 0.217) and number of leaves during P1–P2 ( r = 0.352). On the other hand, during P5–P6, excessive thermal accumulation had a negative effect on dry matter accumulation ( r = − 0.382) and LAI ( r = − 0.316). HTU had a negative effect on LAI during later phenophases ( r ≈ − 0.42 to − 0.48), but it had moderately positive associations with leaf number during P2–P4. During P5–P6, HYTU showed significant negative correlations with both dry matter accumulation ( r = − 0.82) and LAI ( r = − 0.78), suggesting detrimental effects of combined heat and humidity stress. While dry matter accumulation was negatively impacted during P5–P6 ( r ≈ − 0.52), PTU had a positive effect on LAI, with the strongest correlation seen during P4–P5 ( r = 0.421). Plant height ( r = 0.66), rainfall ( r = 0.91), temperature ( r = 0.97), dry matter accumulation ( r = 0.74), and LAI ( r = 0.81) all had positive correlations with yield. The findings highlight the importance of agrometeorological indices in understanding tea phenology, improving yield prediction, and developing climate-resilient management strategies for sustainable Kangra tea production.