Gliricidia sepium tree pollarding and immediate plant growth regulator application to stem cuttings improved seed yield and field performance at Chitedze and Chitala research stations in Malawi

Abstract

Tree germplasm supply has remained a challenge to scaling up agroforestry practices, especially Gliricidia sepium. As a shy seeder, practitioners often consider using gliricidia stem cuttings as an alternative. Methods to rejuvenate old seed stands to increase seed production remain unclear. The objectives of this study were to assess G. sepium (1) rooting ability of stem cuttings prior to planting; (2) field growth performance of trees derived from rooted stem cuttings; and (3) tree pollarding effect on tree growth and seed productivity. Stem cuttings were collected from Karonga, Salima and Machinga districts. These were treated with Seradix® No. 2 either (i) immediately, (ii) four days after planting (DAP), (iii) eight DAP or (iv) no application (control). For the old gliricidia stand, trees were pollarded either at (i) 0.5 m, (ii) 1.0 m, or (iii) 1.5 m above the ground. The results showed early rooting of stem cuttings with immediate Seradix® No. 2 application and 14% of the trees derived from rooted stem cuttings produced seeds two years after planting. For the pollarded old gliricidia stand, tree branches significantly increased with pruning height in the second (P = 0.0173) and third year (P = 0.0301). Gliricidia seed yield significantly increased with time (P = 0.0054). Trees pruned at 1.5 m produced higher seed yield (1320 g/tree) than those pollarded at 0.5 m (555 g/tree) four years after pollarding. It is concluded that pollarding old gliricidia tree stands can rejuvenate trees and improve seed yield.