(no subject)

Luis A. Gurovich lgurovic at sas.puc.cl
Mon Apr 8 18:17:33 EST 1996


EUCALYPTUS WOOD PRODUCTION UNDER IRRIGATION

NATIONAL SCIENCE AND TECHNOLOGY FOUNDATION - CHILE

1995 - 1997


FORESTAL SANTA FE Ltd.
and
PONTIFICIA UNIVERSIDAD CATOLICA DE CHILE

Luis A. Gurovich, Andrés Lyon and Jorge Holmberg


SUMMARY

The study is oriented to define the effect of irrigation in Eucalyptus plantations on: biomass production, wood specific gravity, fiber lenght and lignine characteristics, by means of water production functions, obtained in field experiments. The economic analysis of these production functions will help define the return on investments in irrigation, considering that:

1. With irrigation, the plantation will reach harvesting maturity one or two years earlier, as compared to non-irrigated Eucalyptus plantations growing in the same edapho-climatic condition.

2. Eucalyptus wood production will have a better fiber lenght distribution and lignine content, as related to industry needs, than wood produced on non-irrigated plots.

3. The reconversion of agricultural irrigated soils into Eucalyptus plantations located closer to cellulose industrial facilities is economically feasible, considering actual land prices and decreasing returns of traditional crops cultivated in the area.


WORKING HYPOTHESIS

The reconversion of some irrigated agricultural lands into Eucalyptus wood production for cellulose manufacturing is economically feasible  due to :

1. the reduction on the number of years from plantation to harvesting maturity.

2. the modification of some wood properties qualitative characteristics.


1
3. the reduction on the number of years needed to reach a secondary Eucalyptus growth after the first harvesting, for cellulose production.



MAIN OBJECTIVES

1. To evaluate the effect of irrigation in Eucalyptus plantations on wood development and quality, by means of irrigation technology production functions.

2. To evaluate economic parameters related to investments and operational costs of irrigation, and the cash-flow resulting from wood harvesting precocity and wood industrial quality.

3. To define the magnitude of economically feasible investments in irrigation technology,  needed to incorporate irrigation as a wood production practice on Eucalyptus plantations.


SPECIFIC OBJECTIVES

1. Determine in field experiments water production functions of irrigation technology on Eucalyptus plantations, including:

a. Three month biomass increments for different irrigation strategies, at 4 experimental sites.

b. Yearly root growth for different irrigation strategies.

c. Foliar leaf index and ETcrop, along the irrigation season.

d. Eucalyptus photosynthetic capacity under different water stress conditions.

e. Evaluation of different alternatives to define water stress in Eucalyptus, for its application on irrigation scheduling.

2. Evaluation of different irrigation methods in Eucalyptus wood production.

3. Biomass production of secondary Eucalyptus growth after harvesting.

4. Effects of water stress conditions on wood fiber length, lignine content and cellulose production, including:

a. Hystology studies in radial and longitudinal floem, xylem and cambium samples, obtained from trees under different water management.

b. Wood specific gravity determinations at harvest time.

c. Qualitative characterization of lignines, cellulose and hemi-cellulose in wood at harvest time.

5. Economic evaluation several strategies of supplemental irrigation, as a production practice on Eucalyptus plantations, including:

a. Reduction on the number of years from plantation to harvesting maturity.

b. the modification of some wood properties qualitative characteristics.

c. The reduction on the number of years needed to reach a secondary Eucalyptus growth after the first harvesting, for cellulose production.

d. Irrigation investments, as well as fixed and variable costs needed to implement different irrigation alternatives in Eucalyptus plantations.


METHODOLOGY

Water production functions will be determined experimentally, at field plots under different irrigation regimes, with controlled water application devices (drip irrigation equipment), measuring soil water content profiles by neutrometric, tensiometric and soil sampling techniques.

Two experimental sites will be located at the University experimental farm., near Santiago, and two similar sites will be implemented at Eucalyptus plantations at the VI and VIII Regions, 250 and 750 Km south of Santiago.

At each experimental site, irrigation treatments will be obtained either by the differential drip density method and by the differential drip discharge method. Actual daily ET reposition  will be defined by means of daily standard evaporation pans measurements and a Kc time function, to be continuosly adjusted by daily tensiometric readings and weekly measurements of soil water content profiles, by means of neutrometric, tensiometric and soil sampling techniques. This technique has been used to define by daily approximations a Kc = f[t] function in fruit orchards (Gurovich, 1991).



Both the differential drip density and the differential drip discharge methods enable to obtain, each time the irrigation system is activated, plots with deficit, normal and excesive water applications, being normal irrigation the exact daily ET reposition, determined by standard class A evaporation readings and the Kc = f [t] corresponding value. Also, a non-irrigated plot is considered as a check plot. Accordigly, field plot irrigation treatments will be:

1. Daily reposition of 100% ETa value [check No. 1].
2. Daily reposition of 0% ETa value [check No. 2].
3. Daily reposition of 25% ETa value.
4. Daily reposition of 50% ETa value.
5. Daily reposition of 75% ETa value.
6. Daily reposition of 125% ETa value.
7. Daily reposition of 150% ETa value.
8. Daily reposition of 175% ETa value.


Experimental plot size will be 0.05 hectares within a commercial Eucalyptus plantation, i. e, 125 trees. Four replications are considered, with a total of 32 different plots, in a total area of 1.6 hectares for each experimental site.

At each experimental plot, quarterly (three month) determinations are considered:

- growth rate, by conventional dasometry instruments,
- foliar leaf index (by a light interceptometer),
- photosyntetic activity by means of a photosynthesis analizer)
- total biomass by gravimetry

Once a year, root development will be studied, radially from the trunk and in depth from the soil surface, on trees from each experimental plot, with hydraulic soil washing.

Several alternatives to define soil water strees in Eucalyptus will be compared in selected experimental plots within each experimental site. Alternatives considered are:

a. Infra-red thermometry (Clawson, 1982; Gurovich, 1991)

b. leaf water tension with a Scholander pressure chamber (Peretz et al, 1984)

c. Stomata relative opening, by petroleum yelly infiltration technique, describe by Kanemasu (1975).

To define the optimal investment level for Eucalyptus plantations, a one year experiment with differennt irrigation methods will be conducted, considering uncontrolled inundation, basin, furrow, sprinkler and drip irrigation techniques.

At the end of the experiment, wood samples will be analized by hystology techniques, to define wood quality characteristics; also specific gravity and modules of rupture will be determined for trees grown at different irrigation plots.

During the first season a fifth experiment will be stated at a commercial Eucalyptus plantation just harvested; the objective of this experiment is to evaluate the effect of irrigation on new growth rate, with two irrigation treatments:

a. No irrigation
b. Daily 100% ETa reposition

At this experiment, the same determinations described above will be implemented, with the exception of root growth development.

Economic analysis of results obtained at the field experiments will consist on the Present Net Value, Internal Rate of Returns and Investment Return calculations.


WORKING PLAN

A. Permanent plots (4 experimental sites, 32 plots each):

1. Site selection.

2. Design and instalation of drip irrigation equipment.

3. Planting of 3 experimental plots

4. Irrigation scheduling program, considering soil, plant and climate relations.

5. Dasometry and gravimetric measurements (quarterly).

6. Root development (yearly).

7. Daily tensiometer readings at 30 and 60 cm within the soil profile.

8. Daily measurements of relevant climate data.

9. Every second week, foliar leaf area index and leaf water stress measurements.

10. Three times each season, photosynthetic capacity measurements.

11. Once a year, wood sampling for:

fiber lenght, width and diameter.
lignine content and characterization.
cellulose and hemi-cellulose content
wood specific gravity and module of rupture


B. Comparative irrigation methods field experiment.

1. Design and field implementation of each irrigation method.

2. Quarterly determinations of dasometry parameters.

3. Determination of  Irrigation efficiency components.


C. Irrigation experiment on Eucalyptus re - growth after harvesting.


1. Design and field implementation of a drip irrigation system

2. Monthly dasometry measurements.


D. Economic Evaluation


1. Economic evaluation of field results.

2. Optimization of investment on irrigation technology for Eucalyptus, with a sensitivity analysis for different components of the economic model.
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