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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.