WBC-VIII-Vol.4 – Resources – Forestry, Plantations and ... - BambuSC

produced many shoots early on but fewer as the clumps aged (on average c. 40 shoots per clump in the first year
of measurement, c. 30 in the second and c. 10 in the third year). However, the proportion of marketable shoots
increased over time (Traynor and Midmore 2009).
Appropriate management practices for sustainable culm production
The same production inputs, water, nutrients and management of culm populations influence culm production
and as for shoot production, species has an overriding influence on culm production, in terms of both numbers
and size.
Irrigation
Withholding irrigation altogether (as compared to satisfying evapotranspiration demand) in an environment with
barely 1500 mm of annual rainfall reduces biomass yield by 40% (Zhu et al. 2009), but that is confounded by
also withholding fertiliser. The same effect was evident by withholding winter irrigation at another warmer site
with similar rainfall – culm yield was reduced by 24% compared to full irrigation (Traynor and Midmore 2009).
Irrigation throughout the year at only 50% of pan evaporation reduces culm yield by 15%, not as great as
withholding all irrigation during the dry season. At another warmer site, on a lighter soil, the 50% irrigation
treatment did not affect culm yield, although culm water use efficiency (WUE – based upon weight of culm per
unit of irrigation) was double that of the 100% irrigation treatment (Traynor and Midmore 2009).
In similar trials in the Philippines, in one site in Capiz, neither lack of irrigation nor irrigation supplied only just
before and during the shoot season reduced culm yield compared to the fully irrigated treatment (although both
treatments had higher culm WUEs than the irrigated control – Marquez 2009). In another site with irrigation
treatments, in Ilocos Norte, culms that experienced the reduced irrigation treatments were thinner in diameter
and their biomass lower (Malab et al. 2009).
It has been suggested, based upon experimental data, that sympodial bamboos can dissipate up to 3300 mm/year
rainfall equivalent (Kleinhenz and Midmore 2000), but c. 2000 mm/year offers the best returns in terms of water
use efficiency, both for shoots (if concentrated just prior to and during the shoot season) and for culms.
Fertiliser
As mentioned earlier, nutrient application rates to ensure that leaf nitrogen remains at close to 3% are considered
to be excessive, although bamboo has a great capacity to take up much available soil nitrogen – a luxury uptake
(Kleinhenz and Midmore 2002). Much focus has been on N fertilizer (the most readily available nutrient, and
with the lowest unit cost), but bamboo also responds to potassium, and the nutrient use efficiency if greater than
that for nitrogen and phosphorous (Table 1).
In recent trials in the NT of Australia (Traynor and Midmore 2009), culm yield was unaffected by fertiliser
application in the first year of measurement, and marginally enhanced in the second year – an indication that
perhaps, even for a young plantation at full irrigation, clump water demand was not being met. In Queensland,
VIII World Bamboo Congress Proceedings Vol 4-75