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Estimating water usage of bamboo

Estimating water usage of bamboo
Kleinhenz, V.; Midmore, D.J., 2000
Access to Asian Vegetables, 28, 1-2


Estimating water usage of bamboo

Estimating water usage of bamboo

(RIRDC Project UCQ-9A)

Volker Kleinhenz & David Midmore

(ph (07) 4930 9770, fax (07) 4930 9255)

 

There is tremendous requirement for information about water usage of bamboo in Australia. Commercial producers of bamboo for vegetable shoots and timber are seeking figures to estimate irrigation requirements in this semi-arid country. We have also been asked by governmental agencies, environmentalists and private households to estimate water consumption of bamboo for wastewater dissipation.

 

After reviewing about 200 overseas scientific publications on bamboo agronomy with the greater part of them written in Chinese, we had to conclude that there is no specific information on water consumption of bamboo available. However, water usage of plants essentially depends on their total leaf area and some authors have estimated total leaf biomass and 'specific leaf area' (ie leaf area per unit leaf biomass) for bamboo which makes it possible to calculate total leaf area. If those figures are known, water usage of bamboo can be calculated as the product of total leaf area and transpiration rate. We were unable to find estimates for transpiration of bamboo leaves in the literature and, therefore, measured this for a number of bamboo species currently grown in Australia.

 

Table 1 summarises estimates and measurements on which our calculation of bamboo water usage was based and from where these were derived.

 

Table 1 Estimates and measurements for calculating water usage of mature bamboo

Parameter

Value

Unit

Source

Leaf biomass (dry)

5

[t] [ha]-1

overseas literature

Leaf dry/fresh weight

10

[%]

own measurements

Leaf biomass (fresh)

0.5

[t] [ha]-1

own calculation

Specific leaf area

150

[cm leaf area]2 [g dry leaf]-1

overseas literature

Specific leaf area

15

[cm leaf area]2 [g fresh leaf]-1

own calculation

Leaf area index

7.5

[m leaf area]2 [m soil surface]-2

own calculation

Transpiration rate

2.3

[mmol water] [m leaf area]-2 [s]-1

own measurements

Transpiration rate a

0.04

[ml water] [m leaf area]-2 [s]-1

own calculation

Water usage b

13

[l water] [m soil surface]-2 [day]-1

own calculation

Water usage c

9

[l water] [m soil surface]-2 [day]-1

own estimation

Water usage

3,285

[mm water]

own calculation

a Atomic weight of H2O: 0.018 [g] [mmol]-1

b ie Water usage at maximum transpiration rate for 12 [h] [day]-1

c ie Water usage at estimated average yearly transpiration rate

 

The estimates for leaf area were made based on a measurement for a running bamboo species (P. pubescens) which had 3,900 culms ha-1. Clumping bamboos may have 15 culms clump-1 planted at a density of 250 clumps ha-1 (= 40 m2 clump-1 = 6 7 m planting distance). It follows that one mature clump may transpire (3,300 l m-2 40 m2 =) 132,000 l water year-1.

 

Mature bamboo plant (B. oldhamii) on the Queensland coast

 

Under field conditions we have recommended 2,000 mm water (precipitation + irrigation) per year (Midmore et al., 1998) but actually only prior to and during the shooting season which barely extends to a period of 6 months. Water usage outside of the shooting season may be sizeable if plants are well-watered, therefore, 3300 mm per year (last parameter in table 1) seems to be a good estimate for the capacity of mature bamboo for transpiration under well-watered conditions. Current experiments are refining this estimation. This figure does not imply that for optimal shoot/timber yields such quantity should be available, rather it indicates the maximal water dissipation rate of bamboo.

 

Literature

Midmore, D, Walsh, K, Kleinhenz, V, Milne, J, Leonardi, J, Blackburn, K, 1998: Culinary bamboo shoots in Australia. RIRDC Publication No 98/45. Rural Industries Research and Development Corporation, Barton. ISBN 0 642 54065 9.