Sink efficiency of red gram [Cajanus cajan (L.) Millsp.] as influenced by pottasium and growth regulators

Abstract

The research work entitled “Sink efficiency of red gram [Cajanus cajan (L.) Millsp.] as influenced by potassium and growth regulators” was conducted at College of Agriculture, Vellayani, during 2019-2021. The main objectives were to assess the effect of potassium nutrition and growth regulators on growth, seed yield and dry matter partitioning in red gram and to work out the economics. The field experiment was laid out in randomized block design with 12 combinations of two factors, potassium and growth regulators, as treatments and a control, in three replications, during January - May 2021. The factors included were four levels of potassium (a1 - 0.5 % K2SO4, a2 - 1.0 % K2SO4, a3 - 0.25 % KNO3, a4 - 0.5 % KNO3) and three growth regulators (b1– gibberellic acid (GA3) 75 mg kg-1, b2 - brassinosteroid (BR) 0.1 mg kg-1, b3 - humic acid (HA) 100 mg kg-1). The variety used for the study was APK 1 and the nutrient dose adopted was 40:80:40 kg NPK ha-1. The treatments of foliar spray were given twice, potassium fertilizers, at flower bud and pod formation stages and growth regulators, 30 days after sowing (DAS) and at flower bud stage. The control plot was maintained without foliar application. The results of the study revealed that the plants were significantly the tallest at 60 and 90 DAS (94.59 and 148.87 cm respectively) in a4 (0.5 per cent KNO3). At flowering, the superior number of branches (8.73), leaf area (1662.76 cm2) and the highest root volume and rooting depth were recorded in a4. The number of root nodules was found maximum in a2. Foliar application of GA3 (b1) resulted in significantly taller plants at 60 and 90 DAS, and at flowering, the significantly superior number of branches, leaf area, root volume and the highest rooting depth and root-shoot ratio. The variation in the number of root nodules with the growth regulators was non-significant. Growth attributes were the highest in the interaction, a4b1 (0.5 % KNO3 x GA3), while the nodule number and weight, at flowering were maximum in a1b2 (0.5 % K2SO4 x BR). Treatment effects were significantly superior to control for all parameters, except the number and weight of nodules, which remained comparable. Crop growth rate (CGR) during 30-60 DAS, 60-90 DAS and 90 DAS- harvest, and leaf area index (LAI) were significantly the highest in a4, and among the growth regulators, in b1. The interaction effects were also significantly higher in the a4b1 combination. The individual effects of potassium and growth regulators revealed maximum dry matter partitioning to the shoots followed by that to pods and roots. Among the combinations, the partitioning to the pods was comparatively higher in a4b1 (45.06 %). The treatments were significantly superior to the control with respect to CGR, LAI and dry matter partitioning towards pods and roots, while that to shoots was significantly higher in the control. Chlorophyll and relative leaf water content in leaves at flowering remained comparable, whereas the soluble protein content in leaves was the maximum in a4b1. Foliar nutrition of potassium did not elicit marked variations in the number of days taken to 50 per cent flowering, while yield attributes remained significantly the highest with 0.5 per cent KNO3 application. Seed (1081.33 kg ha-1) and haulm (4837.27 kg ha-1) yields were significantly superior in a4. Among growth regulators, BR induced earliness in flowering (57.6 days) and the yield attributes were significantly the highest in b1. Foliar application of GA3 recorded the maximum seed yield (1100.13 kg ha-1) and haulm yield (4780.82 kg ha-1), the latter was on par with b2 (BR). The interaction effects also revealed significantly the highest values for yield attributes and yield in a4b1. Comparing the treatments with the control, treatment effects were markedly higher. Potassium nitrate influenced the crude protein content in seed favorably and the effect of treatments was significantly superior to the control. NPK uptake was the highest in a4, and among the growth regulators, the maximum uptake of P and K were recorded in b1. Among interactions, the nutrient uptake was significantly higher in a4b1, and in comparision with the control, the treatment effects were superior. The post-harvest analysis of soil did not show any significant variation in pH and organic carbon content, whereas available nutrient status varied significantly and was the lowest in the treatment combination, a4b1. Maximum net income (₹ 85723 ha-1) and benefit cost ratio (2.51) were realized in the treatment combination a4b1, and the net income was 46.4 per cent higher than that in control. Based on the above findings it can be concluded that foliar application of KNO3 and GA3 enhanced growth, sink efficiency and seed yield in red gram. Considering the economics, foliar nutrition with KNO3 (0.5 %) at flower bud and pod formation stages and GA3 (75 mg kg-1), 30 DAS and at flower bud stage, along with the nutrient dose of 40: 80: 40 kg NPK ha-1 can be recommended for cultivation of red gram.