Medicinal plants as intercrops in cassava (Manihot esculenta Crantz)

Abstract

Kerala is considered a treasure house of medicinal and aromatic plants, however, due to indiscriminate harvesting; the existence of most of these plants is under threat. Cultivation is the only option to ensure the continual supply of high quality raw materials without diminishing natural resources. Due to small holding size and a greater focus on cash crops, the scope for commercial production of medicinal plants as a pure crop in Kerala is restricted. So, the practical alternative is to bring them under intercropping with priority crops such as food and commercial crops. Cassava (Manihot esculenta Crantz) is the most important starchy root crop grown in the tropics. The wide spacing, together with slow initial growth and development, makes cassava compatible to intercropping with short duration annual crops. The present study entitled “Medicinal plants as intercrops in cassava (Manihot esculenta Crantz)” was carried out at the Agronomy farm, Department of Agronomy, College of Agriculture, Vellanikara from September 2020 to April 2021 to assess the feasibility of intercropping cassava with the medicinal plants Indigofera tinctoria, Plectranthus vettiveroides and Sida alnifolia. The experiment was laid out in Randomized Block Design (RBD) with 10 treatments replicated thrice. The treatments included sole crops of cassava and medicinal plants, cassava + single row of medicinal plants, and cassava + double rows of medicinal plants. The observations on growth, yield and yield attributes of main and intercrops, and quality parameters of medicinal plants were recorded. Competitive indices and economics of cultivation were also computed. Intercropping significantly influenced the growth and yield attributes of both main and intercrops. With respect to plant height of cassava, significant variation was observed only at later stages of crop growth. Shorter cassava plants were observed when intercropped with Sida alnifolia (162.84 cm). In general, medicinal plants grown under intercropping system recorded taller plants, except for Indigofera, where sole cropping resulted in taller plants.The sole crop of cassava produced higher per plant tuber yield of 3.24 kg (32417 kg/ha) and was at par with cassava with single row of Plectranthus (3.12 kg/plant). The lowest tuber yield was recorded when cassava was intercropped with double row of Sida (1.77 kg/plant). Similar trend was observed in itop yield and dry matter production per plant. The yield of medicinal plants was the highest in sole crops, followed by single row intercropping and double row intercropping. Same trend was observed for quality parameters of medicinal plants. The quality of Indigofera tinctoria, expressed by indican content, was higher in sole crop (1.40 per cent) and was on par with single row inter crop (1.39 per cent). Sole crop of Plectranthus vettiveroides registered the highest essential oil content of 0.60 per cent, followed by cassava + single row of Plectranthus (0.40 per cent). Sole crop of Sida alnifolia produced highest total alkaloid (3.07 per cent) and was at par with single row intercrop (2.94 per cent). Cassavas intercropped with double rows of medicinal plants were more efficient in controlling weeds than sole crop of cassava or cassava + single row of medicinal plants. Sole crop of cassava recorded the highest total weed density and dry matter production at 30 DAP, 60 DAP and 90 DAP. Sida alnifolia controlled the weeds more effectively than other medicinal plants, both as sole crop or as intercrop with cassava. Competition indices like land equivalent ratio (LER), relative crowding coefficient (K or RCC), competitive ratio (CR), cassava equivalent yield (CEY) and aggressivity were assessed for evaluating intercropping efficiency. All intercropping systems recorded LER of values greater than one, indicating the yield advantage over sole cropping. The highest LER (1.41) was recorded when cassava was intercropped with double row double row of Plectranthus vettiveroides and LER was lower when Sida alnifolia was intercropped either as single row or as double rows (1.01 and 1.05 respectively). Higher RCC and CR values and positive aggressivity values for cassava indicated dominance of cassava over medicinal plants. K (RCC) of all treatments was greater than one, indicating yield advantage of the system. The highest CEY was recorded for cassava + Indigofera as double row, with cassava equivalent yield of 43895 kg/ha, and the lowest CEY was for sole crop of Sida alnifolia (3000 kg/ha). Among the medicinal plants evaluated, Indigofera tinctoria, either as double row or as single row, could be recommended as the best medicinal intercrop for cassava. Intercropping cassava with single row Plectranthus vettiveroides was the next best alternative.