Influence of manual and chemical nipping and different castor hybrids on physiological and yield attributes and yield under irrigated ecosystem of South India

A field experiment was carried out in Tapioca and Castor Research Station, Yethapur Salem, Tamil Nadu, India, to study the effect of castor hybrids and nipping practice on the physiological and yield of castor in irrigated conditions. The experiment was laid out in a splitplot design with three replications. The main plot treatments comprised four castor hybrids of M1- YRCH -1, M2-YRCH-2, M3- ICH-66, M4- DCH-519 and sub-plot treatments have various nipping of S1-no nipping, S2-manual nipping @10th node, S3-manual nipping @ 12th node and S4-Chemical nipping @ 12th node mepiquat chloride 200 g/ha have been imposed. Among the castor hybrids, M2-YRCH -2 recorded significantly highest physiological parameters., chlorophyll content 53.0 (spade value), Photosynthetic rate (22.0 µ mol/m2 /sec), Transpiration rate (10.5 mmol/m2 /sec) and stomatal conductance (269 mmol/m2 /sec), Concerning yield attributes, highest number of spike/plantof 7.9, spike length of 73.6 cm, number of capsules /spike 158.6 were recorded with YRCH2 (M2), spike yield of 2327 kg/ha seed yield of 1820 kg/ha over the other hybrids. About nipping practices, S4- chemical nipping with mepiquat chloride 200 g/ha recorded, Significantly highest physiological parameters Viz., chlorophyll content 57.0 (spade value), Photosynthetic rate (27.2 µ mol/m2 /sec), Transpiration rate (11.2 mmol/m2 /sec) and stomatal conductance (387.6 mmol/m2 /sec) and yield attributes like., number of spike /plant of 9.0, number of capsules /spike 167.7, spike length of 75.4 cm, spike yield 2487 kg/ha and seed yield of 1975 kg/ha. From this experiment, it is concluded that raising YRCH-2 castor hybrid combined with chemical nipping of mepiquat chloride @ 200 g/ha (M2S4) recorded the highest yield of 2198 kg/ha, net return of 92849 Rs/ha and benefit-cost ratio of 3.31. Hence, adopting nipping under conditions can enhance the physiological parameters and yield of the castor.