Standardization of vegetative propagation of fodder calliandra (Calliandra calothyrsus Meissn.) using coppice cuttings

Abstract

Calliandra calothyrsus Meissn is a leguminous fodder tree that has recently become the subject of intensive study and cultivation due to its protein-rich foliage and other uses. The species is especially useful in humid tropical climates and on acidic soils, where other agroforestry plants struggle. It is predominantly used outside its native range, in areas where high population density places pressure on limited land resources, and where agroforestry systems are developed mainly to maintain and sustain agricultural production. Vegetative methods of propagation have been examined due to the limitation in the availability of calliandra seeds for planting. C. calothyrsus cannot be easily multiplied by planting leafless stakes directly in the ground, however various low-cost vegetative propagation techniques have been studied for the growth of C. calothyrsus plants. However, detailed studies on vegetative propagation are absent in this species especially under humid tropical conditions of Kerala. With this background, the present study was conducted to standardize a protocol for large scale planting stock production of fodder calliandra from coppice cuttings, by assessing the influence of types of cuttings and concentration of growth regulators such as IBA and NAA; and the influence of season on the root and shoot development in vegetatively propagated calliandra. The proposed nursery study was conducted as two separate trials during rainy period (June 2021 to December 2021) and dry period (January 2022 to August 2022) at College of Forestry, Vellanikkara. An existing 4-year-old calliandra plantation was cut back at 30 cm height from the ground during June 2021(rainy season trial) and during January 2022 (dry season trial) and allowed to coppice. Two-month-old coppice shoots were taken for vegetative propagation during both the seasons. Three- nodded softwood and semi hardwood cuttings of uniform size were prepared from the apex and basal portions of the coppice shoot. The cuttings were treated with the solutions of two plant growth regulators NAA or IBA in different concentrations i.e., 0, 50, 100, 200 and 250 mg l-1 overnight and kept in soil based/vermiculite rooting media and under mist/non-mist propagation chambers for rooting. There were 19 treatments for each trial laid out in CRD design, which included all possible combinations of soft wood/semi hardwood cuttings treated with 4 concentrations of NAA/IBA along with untreated control, and one absolute control viz., calliandra planting stock raised from seeds, for relative comparison. Fifteen branch cuttings constituted one replication and there were three replications per treatment. All the treated as well as untreated cuttings failed to sprout and root under non-mist propagation conditions like that of shade house and polytunnels during both the seasons. However, 6 treatments in rainy season and 8 treatments in summer season were successful when kept under the controlled conditions of mist chamber. Cuttings placed in soil based rooting medium failed under both mist and non-mist conditions. Vermiculite medium was also unsuccessful under non-mist conditions, while successful sprouting and rooting of cuttings was recorded when kept in vermiculite rooting medium under the mist chamber. Calliandra calothyrsus coppice cuttings showed significant improvement in sprouting percentage, number of days to initiate sprouting, shoot length, rooting percentage, number of days to initiate rooting, fresh and dry weight of stem, root and leaves and overall survival percentage, when treated with 50 ppm NAA. In general, softwood cuttings performed better than semi hardwood cuttings. However, apparently better response was observed for number of sprouts, number of leaves and root length with IBA at 50 ppm. The overall survival percentage of cuttings with successful rooting and shooting was higher for soft wood cuttings treated with 50 ppm NAA during rainy (68.8%) and summer season (80%), followed by respective value of 48.88% for 50 ppm IBA in both seasons. While the calliandra planting stock raised from seeds showed 100 per cent survival during both the seasons. Among treated cuttings, duration of planting stock production was also lower for 50 ppm NAA during both the season (100 and 110 days) followed by 50 ppm IBA treated cuttings. In general, the lower concentration (50ppm) of NAA/IBA gave higher shoot and root parameters for calliandra coppice cuttings and was found to be on par with that of calliandra seedlings. Comparing seasons in general, shooting and rooting parameters was higher in summer season compared to rainy season for most of the treatments. In conclusion, calliandra can be vegetatively propagated from softwood coppice cuttings by overnight soaking with 50 ppm of NAA and using vermiculite as rooting medium under controlled conditions of mist chamber, preferably during summer season. 50 ppm IBA was the second-best treatment. The shoot and root parameters of vegetatively propagated calliandra planting stock was on par with that of calliandra seedlings.