The effects of nitrogen and lime application, broadcast and banded basal fertilizer (P, K, Cu Zn and Mo), and depth of cultivation on growth of leucaena (Leucaena leucocephala) seedlings on a red-yellow podzolic soil (Ultisol), were investigated at The University of Queensland, Mt. Cotton Research Station from December, 1982 to March 1983.
The experiment was a split-plot design with depth of cultivation as mainplots and all combinations of nitrogen, lime and method of basal fertilizer application as subplot treatments. Two harvests were taken after 5 and 15 weeks to assess seedling growth in terms of plant height, leaf number, shoot dry matter yield and nodule dry weight. A wire mesh fence was constructed after hares had defoliated all plants during weeks 5 and 8.
After 5 weeks growth, seedling height was significantly increased by nitrogen and lime application and by banding of basal
fertilizer, but except for nitrogen, those effects had disappeared by 15 weeks. Average heights after 5 and 15 weeks, of seedlings receiving nitrogen and lime, were 5.8 and 24.9 cm, respectively, compared to 4.5 and 17.1 cm respectively, without nitrogen and lime. Deep cultivation significantly reduced seedling height at the first harvest but there was no significant effect by the second harvest.
A significant increase in leaf number was obtained from plants treated with nitrogen, lime, banded basal fertilizer and shallow cultivation; maximum leaf number was 8.7 leaves per plant after five weeks of growth and was achieved from plants receiving a combination of the above treatments.
At the second harvest, liming significantly increased nodule dry weight from 0.06 to 0.1 g plant-1 whilst nitrogen and banded basal fertilizer had no significant effects.
Shoot dry matter yield of seedlings was
significantly increased by nitrogen and lime application. At the first harvest, maximum increase in shoot dry matter, from 0.14 to 0.25 g plant-1 was recorded for seedlings treated with nitrogen, while lime increased shoot dry matter from 0.18 to 0.20 g plant-I. At the second harvest, shoot dry matter was increased from 4:0 to 7.0 g plant-1 and from 5.0 to 6.0 g plant-1 by nitrogen application and liming, respectively. Banding of basal fertilizer significantly increased shoot dry matter yield of seedlings at the first harvest but the effect was not evident at the second harvest. There were no significant effects of depth of cultivation on shoot dry matter of seedlings but plants growing on a deep seedbed had consistently lower shoot dry matter than plants on a shallow seedbed.