Combating alternate bearing tendency in litchi (Litchi chinensis) cultivars through paclobutrazol and potassium nitrate

Abstract

A field experiment was conducted during 2018–2020 at ICAR-National Research Centre on Litchi, Muzaffarpur, Bihar to study the effect of paclobutrazol (PBZ) on endogenous hormonal status of shoot buds, flowering, yield and fruit quality attributes of litchi (Litchi chinensis Sonn.) cv. Shahi which was also affected by foliar spray of micronutrient solution and amino acids complexes. The trees of litchi cv. China was treated with PBZ (2.5 g a.i./m canopy diameter) and other chemicals like KNO₃ (2.0 %), prohexadion-Ca (pro-Ca) (0.5 g/L), salicylic acid (SA) (2000 ppm), KH₂PO₄ (0.5%) and spermidine (Spd) (0.01 mM) and girdling. The floral shoots of litchi cv. Shahi had very poor IAA content with high GA₃, non-floral shoots showed reverse trend, means PBZ (2–3 g) suppressed GA₃ and IAA, and enhanced ABA and cytokinins contents to favour flowering. The 2.0 g PBZ brought highest yield (755.67 fruits/tree), high vitamin C (26 mg/100 g pulp), better TSS over other doses. Micronutrient solution (Zn, Fe, Cu, B, Mn, Mo) and amino acids complexes like ambition-multiplex-ambition (each spray @2 mL/L alternatively as pre-harvest) ensured high tree girth, more floral panicles and significantly higher fruit yield. In alternate bearer litchi cv. China, every year foliar spray of KNO₃ (2.0%) during last week of September month was the most effective way to bring consistency in bearing (2,158 fruits/tree). The KNO₃ (2%) and PBZ (2.5 g) application might bring excellent fruit quality in terms of TSS and vitamin C content in litchi.