Effect of pot size and potting mixture on growth performance of Calliandra calothyrsus seedlings at Bako tree nursery.

Calliandra calothyrsus Meissn. is a versatile tree species with multiple values. A nursery experiment on this multipurpose tree species was conducted at Bako, Western Oromia, Ethiopia, in order to determine the optimum pot size and potting mixture for practical use. The experimental treatment constituted three pot sizes (8cm, 10cm, and 12 cm) and four varying proportions of nursery soil by volume (3 part local soil: 2 part sand: 1 part forest soil, 3 part local soil: 1 part sand: 2 part forest soil, 3 part local soil: 2 part sand: 1 part farm yard manure, and 3 part local soil: 1 part sand: 2 part farmyard manure) laid out in a randomized complete block design with three replications. Results at the nursery revealed that seedling performance was significantly (P<0.01) affected by both difference in pot size and soil mixture, but the interaction between pot size and soil mix ratio was not significant. Accordingly, the performance of Calliandra seedlings was significantly higher for the larger pots (10 cm and 12 cm) than for the smaller (8cm). Moreover, seedlings growth was significantly higher for potting mixture with higher organic matter (3 part local soil: 1 part sand: 2 part farmyard manure) than for those with lower organic matter (3 part local soil: 2 part sand: 1 part forest soil), but seedling survival was significantly higher for the latter (98%) than for the former (77%), which leads to the need for trading off between survival and seedling growth. Therefore, for practical purpose it is advisable to use the 10 cm pot size and potting substrate with modest organic matter (3 part local soil: 1 part sand: 2 part forest soil). But the case might be different under field condition after out-planting, and hence further study is also required under field conditions to evaluate the field performance of Calliandra seedlins raised under different pot sizes and nursery soil mixture.