82 Growing seedlings of sandalwood in containers Effect of container type and size on the growth and quality of seedlings of Indian sandalwood (Santalum album L.) D. Annapurna 1 , T.S. Rathore 1,2 and Geeta Joshi 1 1 Tree Improvement and Propagation Division, Institute of Wood Science and Technology, 18th Cross, Malleswaram, Bangalore 560 003, India 2 Email: tsrathore@iwst.res.in Revised manuscript received 16 September 2003 Summary Studies were carried out to determine the effects of container type and size on the growth and quality of seedlings of Indian sandalwood (Santalum album L.), an over-exploited hemi-root parasite. Three types of container, viz. root trainers (150, 270, 300, 450 and 600 mL), polythene bags (polybags) (600, 1000 and 1500 mL) and plastic containers (1000 mL) were used with a potting medium that consisted of sand, soil, compost, burnt rice husk and charcoal in the ratio of 5:3:10:1:1. Cajanus cajan was used as a primary host in all treatments. Survival and overall growth of sandalwood seedlings 6 mo old, in terms of height, collar diameter, seedling biomass and root– shoot ratio, were best in root trainers, and next best in plastic containers. Among the root trainers, the 600 mL size was optimum for most of the parameters of seedling quality, including height (20.4 cm), total dry weight (3.06 g), shoot dry weight (1.66 g), root dry weight (1.41 g) and quality index (0.37). This size was followed by the 270 and 300 mL root trainers. Despite the large size of the polybags (600–1500 mL), seedling growth in these was poor. Root coiling and poor root development affected root dry weight (0.13–0.39 g) and the quality index (0.03–0.05). Good quality seedlings >20 cm high, >3.0 mm in collar diameter and with an 0.3 quality index can be produced in 6 mo in 600 mL root trainers. Most of the parameters of seedling quality (seedling height, collar diameter, seedling biomass and quality index) of seedlings grown in 270 mL block-type root trainers were comparable with those of seedlings in 1000 mL plastic containers. This result encourages further reduction in container size from 600 mL to 270 mL by better managing nutrition and screening for better primary hosts. Keywords: seedling growth; quality; containers; container grown plants; planting stock; Santalum album; Cajanus cajan Introduction Indian sandalwood (Santalum album L.) is a hemi-root parasite, highly prized for its fragrant wood and oil. Over-exploitation and illicit felling has resulted in a great decline in the population of sandalwood in natural habitats, and it is considered a threatened species (Meera et al. 2000). Production of sandalwood has fallen from 4000 t during 1997 to 1000 t during 2000, and prices of sandalwood have increased from Rs 0.16 million t –1 during 1990– 1991 to Rs 0.65 million t –1 during 1999–2000 (Ananthapadmanabha 2000). While the remaining natural resource cannot meet international demand for sandalwood and oil in a sustainable manner, it is an important gene resource for India and Indonesia. Plantations based upon it are a potential source of the wood and oil. The genetic and physical quality of planting stock greatly influences survival, growth and productivity of the subsequent crop. In this paper, the expression ‘quality of seedling’ integrates genetic (seed source), morphological (seedling height, collar diameter, sturdiness and root–shoot ratio) and physiological (nutrition and root growth potential) characteristics. These attributes when taken together ultimately determine seedling performance. Traditional nursery practice entails raising seedlings in polythene bags (polybags) using soil, sand and farmyard manure (FYM) as a potting medium. Such mixtures may produce seedlings with good shoot development but poor root systems (Miller and Jones 1995). In India, S. album seedlings are conventionally raised in polybags of 1500 mL capacity (13 cm x 30 cm size) using a potting mixture of sand:soil:FYM in a 2:1:1 ratio, with Cajanus cajan as a pot host. This produces a plantable seedling 30 cm high with dark brown stem in 6–8 mo (Rai 1990). Problems commonly associated with this conventional practice are the bulk, poor nutritional status and poor aeration of the medium, limited root fibrosity, root coiling, and difficulty in maintaining and managing the host. A consequence is poor survival in the nursery and field. These problems can be addressed by the use of a balanced potting mixture, by using an optimum type and size of container, by applying supplementary nutrition and by choosing the best primary host species. In Western Australia, black plastic containers 180 mm high and 100 mm diameter (1500 mL), have been used with a potting medium of sand:peat:perlite in the ratio of 3:2:2 for the production of S. album seedlings in 5–6 mo, using Alternanthera nana as a primary (pot) host (Radomiljac 1998). Containerised seedling production has been widely used since the early sixties. The practice improved seedling survival and management as compared to bare-root seedling production (Xuo and Gao 1984). The primary function of any container is to hold a discrete supply of growing medium, which in turn supplies water, air, mineral nutrients and physical support to the seedling. Apart from these functions, the containers must inhibit root spiralling and root coiling and encourage root pruning at the base of the cell, which favours a more fibrous root system (Jinks 1994).