Physiological Response of Blackgram Varieties to Foliar Nutrition and Growth Regulators under Partial Shade in Coconut Orchard in Kerala

Background: Coconut is one of the major plantation crops in Kerala which are planted at a wider spacing of 7.6 m × 7.6 m giving an ample opportunity for growing intercrops. To enhance soil fertility and productivity of crops inclusion of legumes is a viable option. Blackgram, though a shade sensitive crop performs well in partially shaded coconut gardens due to fast growing nature. The unique ability of biological nitrogen fixation, soil amelioration, carbon sequestration, low water requirement and capacity to withstand extreme drought, pulses have remained an integral component of coconut based cropping system. Since blackgram is a shade sensitive crop, to increase the productivity of blackgram in coconut garden, foliar spray of nutrients and growth regulators is a viable option. Under, shaded or stressed situations, nutrients and plant growth regulators provide optimum vegetative growth by regulating plant growth and architecture. The primary objective of the present study was to investigate the impact of foliar nutrition and growth regulator application on the physiology and yield of different blackgram varieties. Methods: A field trial was conducted at College of Agriculture, Vellayani, Kerala, India during rabi 2020 and summer 2020-21. To find the performance of five blackgram varieties. The treatments consisted of five performing blackgram varieties under partial shade viz; Sumanjana, DBGV 5, VBN 5, VBN 6, CO 6 and foliar sprays of nutrients (19:19:19 NPK, sulphate of potash) and plant growth regulators [naphthalene acetic acid (NAA) and salicylic acid (SA)] alone and in combinations in split plot design at 45 and 60 days after sowing (DAS). Result: The study identified Sumanjana and DBGV 5 as shade adaptive varieties with suitable physiological traits. In both seasons, a higher stomatal conductance and lower stomatal index were observed, indicating a more efficient allocation of resources towards the photosynthetic machinery. Foliar spray of 19:19:19 (1%) and NAA at 40 mg/L and SA at 100 mg/L at 45 and 60 DAS resulted in higher seed yield, dry matter production and also higher net income and benefit cost ratio for these two varieties.