Irrigated guayule — Production and water use relationships

Agricultural Water Management, 10 (1985) 95--102

95

Elsevier Science Publishers B.V., Armterdam - - P r i n t e d in The Netherlands

IRRIGATED GUAYULE --PRODUCTION AND WATER USE RELATIONSHIPS

D.A. BUCKS 1, F.S. NAKAYAMA', O.F. FRENCH ', W.W. LEGARD' and W.L. ALEXANDER 2

'U.S. Water Conservation Laboratory, 4331 East Broadway, Phoenix, AZ 85040 (U.S.A.) :Mesa Agricultural Center, Mesa, A Z 85201 (U.S.A.) (Accepted 16 January 1985)

ABSTRACT Bucks, D.A., Nakayama, F.S., French, O.F., Legard, W.W. and Alexander, W.L., 1985. Irrigated guayule -- production and water use relationships. Agric. Water Manage., 10: 95--102. Interest in developing the guayule plant (Parthenium argentatum Gray) as a source of natural rubber has increased in the United States and other countries during the last decade. A comprehensive study was initiated to obtain information on the production and water-use relationships for guayule. Water-use efficiencies for three cultivars after 2 years ranged from 0.70 to 0.85 kg/m 3 for dry matter, 0.045 to 0.055 kg/m 3 for resin, and 0.03 to 0.04 kg]m 3 for rubber production. The dry matter, resin, and rubber yield were shown to be linearly related to evapotranspiration. Large quantities of irrigation water were needed to get high yields in this short period of time. Relating yield and crop stress on a seasonal basis indicated that guayule grown in an arid environment was more sensitive to water stress in the latter than the first half of the year. Although the drought tolerance characteristics of the guayule crop permits flexibility in irrigation scheduling, the irrigation water requirement can be high in order to increase yields and shorten the harvest time to 3 years or less.

INTRODUCTION

Limited data are available on plant water relations for guayule (Parthenium argentatum Gray), e.g. biomass production per unit of water applied, resin and rubber production per unit of water applied, and yield versus plant water stress conditions (Hammond and Polhamus, 1965). An earlier report of Retzer and Mogen (1947) indicated that the highest rubber percentages can be obtained from plants under frequent to moderate periods of water stress, but the highest rubber yields would come from the large-sized unstressed plants. Their data also showed that the best compromise between stress and yield for 2-year-old plants appeared to be at water applications Contribution from Agricultural Research Service, U.S. Department of Agriculture.

0378-3774/85/$03.30

© 1985 Elsevier Science Publishers B.V.

96 of 375 to 650 ram/year with approximately 7--9% rubber and 4500-7800 kg of shrub per ha. Thus, the water-use efficiencies for guayule rubber production in the 1940's ranged from about 0.023 to 0.032 kg/m 3 of water applied. The objective of this paper is to present the production and water use relationships for three guayule cultivars grown in central Arizona during the early stages of plant growth under a wide range of irrigation regimes. MATERIALS AND METHODS Seedlings of three guayule cultivars (593, N565-II and 11591) were established on a 0.5-ha site during the 1st week o f April 1981 in central Arizona. Details on greenhouse seedling production, transplant establishm e n t methods, experimental design, planting density, and irrigation practices were described earlier (Bucks et al., 1985a). Procedures on the measurem e n t of soil water contents and plant canopy temperatures in order to estimate evapotranspiration (ET), crop water stress indices (CWSI), and stress degree days (SDD) were also discussed in the first paper (Bucks et al., 1985a). Determinations of plant heights, weights, resin and rubber contents, and resin and rubber yields for periodic harvests were discussed in the second paper (Bucks et al., 1985b). Six different irrigation treatments replicated four times were based on applying irrigation water when a preselected portion o f the soil water was depleted in the effective rooting depths of 0 to 1.2-m for the last 6 months o f 1981 and 0 to 1.8-m depth for all of 1982. The six irrigation treatments used were as follows: IL, irrigate at 60% depletion (wet); I2, irrigate at 70% depletion (wet); I3, irrigate at 80% depletion (medium); I4, irrigate at 90% depletion (medium); Is, irrigate at 90% depletion, plus 2 weeks delay (dry); I6, irrigate at 90% depletion, plus delay to give only three irrigations per year (dry). RESULTS AND DISCUSSION Data on water applied, soil water contents, and evapotranspiration were presented in the first paper (Bucks et al., 1985a), and on plant growth, production, and production cycles in the second paper (Bucks et al., 1985b). Relationships between dry m a t t e r production versus cumulative ET for whole plants (above-ground material plus roots) and clipped plants (above a 100-ram height), based on seven harvest dates, were as follows: DMW = 0.63 + 0.0075ET,

S a = 0.39,$b-- 0.0003, R 2 = 0.94

(1)

DMC = 0.10 + 0.0048 ET, Sa -- 0.27, Sb = 0.0002, R 2 = 0.93

(2)

97 where DMW is the whole plant dry matter production (t/ha), DMC the clipped plant dry matter production in (t/ha), ET the cumulative evapotranspiration (ram), Sa standard error of intercept, Sb standard error of slope, and R 2 coefficient of determination. The intercept for the clipped plants is considerably lower than for the whole plants. The ratio of the slopes for the clipped to whole plant harvest was 0.64, which indicates that slightly less than 64% fo the shrub biomass could be obtained with the clipping process compared with whole plant harvesting. Equation 1 is shown in Fig. 1 where each of the datum points represents 24 harvested plants averaged for the three cultivars and a single irrigation treatment. Linear regression equations for resin yield versus cumulative ET for whole plant and clipping harvests were as follows: REW = - 1 8 . 7 + 0 . 5 1 E T ,

Sa = 25.1, Sb = 0.019, R : = 0.95

(3)

REC = - 4 2 . 6 + 0.35 ET,

Sa = 22.6, Sb = 0.018, R 2 = 0.91

(4)

where REW is the whole plant resin yield (kg/ha), REC the clipped plant resin yield (kg/ha), and ET the cumulative evapotranspiration (mm). The ratio of the slopes for the clipped versus the whole plant harvest is 0.69, which suggests that up to 69% o f the resin yield can be obtained by harvesting only the upper portion of the plant. I

I

IRRIGATION

25 '~ --

I

I SEVEN WHOLE

TREATMENT

= "]~1 WET

• " I 4 MEDIUM

• ,]'2WET o-Z3MEOIUM

• " I 5 DRY • " I 6 DRY

AVERAGE of CULTIVARS " 5 9 3 , N 5 6 5 - ] I , 11591

i PLANT HARVESTS

I

/ ~

=

E

~

t5

~F-

=

°m •

•

a

10 ~,

AiI

• Am •

• •

<~ r~ w

~>

W • 0.6:5 + 0 . 0 0 7 5 ~

'

~

=

•

ET

R2"094

5

i 1 li, •

i 0

500

I

I

I000 1500 CUMULATWE EVAPOTRANSPIRATION

I

I

2000 2500 ( E T ) , m m of Water

I 5000

Fig. i. Average dry matter production versus cumulative evapotranspiration of seven whole plant harvests for three guayule cultivars under six irrigation treatments at Mesa, AZ, 1981--82.

98 Relationships for rubber yield versus cumulative ET were as follows: RUW = - 2 7 . 4 + 0.37 ET,

Sa = 23.3, Sb = 0.018, R 2 = 0.91

(5)

RUC = - 2 8 . 4 + 0.24 ET,

Sa = 18.1, Sb = 0.014, R: = 0.88

(6)

where RUW is the whole plant rubber yield (kg/ha), RUC the clipped plant rubber yield (kg/ha), and ET the cumulative evapotranspiration (mm). Equation 5 is shown in Fig. 2 along with the original datum points. The intercepts were nearly the same for both equations, and the ratio of the slopes for the clipped versus whole plant harvest was 0.65, which substantiates the rubber yield data in a previous paper {Bucks et al., 1985b) indicating that as much as 65% of the rubber could be obtained by clipping rather than by harvesting the entire plant. Equation 1 through 6 show that resin and rubber yields are highly dependent on the amount o f water being supplied to the guayule plant. Furthermore, comparison o f the resin-rubber--ET equations suggests that young guayule plants can produce at least 50% more resin than rubber. A number of potential economic uses have been proposed for resin that could possibly be more valuable than rubber in the future (Bonnet, 1975; National Academy o f Sciences, 1977; Foster et al., 1979). i

I

I

1

IRRIGATION TREATMENTS o,Z I WET I000

I

• =Z4 MEDIUM

/

" "Z2 WET •=15DRY o=1"3 MEDIUM • =I 6 DRY N565-'IT,

/

~

,/

•

AVERAGE OF CULTIVARS 593,

I

SEVEN WHOLE PLANT HARVESTS

/

r

11591

80C

600 m m

o o

•

•

w

w

••

•

o

=RUW • - 27.4 + 0.37 ET

~'00

~

• j=e

0

. •

o

I

500

••

2 RZ=O.91

I

1

I

I000 1500 ZOO0 CUMULATIVE EVAPOTRANSPIRATION (ET),mm of

I 2500

I 3000

water

Fig. 2. Average rubber yield versus cumulative evapotranspiration of seven whole plant

harvests for three guayule cultivars under six irrigation treatments at Mesa, AZ, 1981--82.

99 Examples of water-use efficiencies for other crops now raised in the southwestern United States are as follows (Doorenbos and Kassan, 1979): alfalfa with 10--15% moisture achieves 1.5--2.0 kg/m 3 after the 1st year; lint c o t t o n with 10% moisture ranges from 0.15 to 0.2 kg/m 3, and citrus fruit with about 85% moisture gives about 2.0--5.0 kg/m 3. Relationships describing the water-use efficiencies for dry matter, resin, and rubber yield of guayule versus cumulative evapotranspiration were as follows: DMWE = 0.94

REW

E

=

0.084

RUWE = 0.087

41.9 ET 10.7 ET 20.9 ET

7.37 × 10 -s ET,

R: = 0.94

(7)

2.98 X 10 -5 ET + 7.20 × 10 -9 ET 2, R 2 = 0.95

(8)

3.55 X 10 -s ET + 7.07 × 10 -9 ET:, R 2 = 0.93

(9)

where DMWz is the dry matter water-use efficiency (kg/m3), REWE = resin water-use efficiency (kg/m3), RUWE the rubber water-use efficiency in (kg/m3), and ET the cumulative evapotranspiration (mm). Water-use efficiencies for dry matter and resin production tended to peak after about 700 mm of ET, whereas the water-use efficiency for rubber yield did not peak until about 1000 mm of ET. After the initial plant growth, water-use efficiency for dry matter production ranged from 0.70 to 0.85 kg/m 3, for resin yield ranged from 0.045 to 0.055 kg/m 3, and for rubber yield ranged from 0.030 to 0.040 kg/m 3 based on ET values. Seasonal variations, plant age, and growing conditions will affect these efficiencies. However, a fairly definite a m o u n t Of guayule production can be predicted for a unit of water as shown by the water-use efficiency curve for guayule rubber production versus ET (Fig. 3). New improved cultivars could increase these efficiencies, but m a y only change these relationships by a multiplication factor. Relative rubber yield increases between whole-plant harvest dates of 15 December 1981 to 15 July 1982, 15 July 1982 to 15 January 1983, and 15 December 1981 to 15 January 1983 (representing production changes for the entire second season of growth) are plotted versus cumulative stress degree days (E SDD) and mean crop water stress index (CWSI) in Figs. 4 and 5, respectively. In all cases, the wet (I,) irrigation treatment had the largest yield increase and was given the base value of 1.0. The consistancy of the six irrigation treatments is shown by similar ranges in 2: SDD and mean CWSI for the first and second half of the 1982 calender year. Also the following seasonal equations for yield increase versus Z SDD and mean CWSI showed similar coefficients of determination: RYI = 0 . 5 5 - - 4 . 3 X 10 -4 Z SDD,

Sa = 0.037, S b = 7.1 X 10 -s, R 2 = 0.90 (10)

RYI = 1.19 -- 1.02 CWSI, Sa = 0.096, Sb = 0.165, R 2 = 0.91

(11)

100 i

|

I

O.OE

~

0.07

e=~: t WET • = I 2 WET • = I 3 MEDIUM

!

SEVEN WHOLE PLANT HARVESTS

IRRIGATION TREATMENT e = I 4 MEDIUM • = I 5 DRY , * - I 6 DRY

RUW E

=0087- - ' ~ - -

AVERAGE OF CULTIVARS 593, N565-'n', 1159t

3.55xlO'5ET+7.07xlO'9ET 2

R 2 =0.93

I,-

~ o.o8 >" 0 0 5

o •

004

~

o Q

@

0.03

w 0.02 2~

er bJ

0.01

I

I

|,

I

I

I

500

I000

1500

2000

2500

3000

CUMULATIVE

EVAPOTRANSPIRATION

(ET).mm of water

Fig. 3. Average water-use efficiency for rubber yield versus cumulative evapotranspiration of seven whole plant harvests for three guayule cultivars under six irrigation treatments at Mesa, AZ, 1981--82.

where RYI is the relative yield increase in the 2rid year from 0 to 1.0 [ ( A Y / ~ Y m a x ) , with A y the yield increase and ~Ymax the m a x i m u m yield increase for I1 (wet) treatment], Z SDD the summation o f stress degree days (°C), and CWSI the mean crop water stress index from 0 to 1.0. Off a seasonal basis, a 2: SDD approaching greater than - 1 0 0 0 ° C stress degree days (the accumulation of differences between plant canopy and air temperatures) and mean CWSI exceeding 0.2 could decrease the potential for high rubber yields significantly. Similarly, Pinter et al. (1983) obtained a linear and inverse relationship between cotton yield and CWSI that suggested a yield decrease would possibly occur when the CWSI is permitted to rise above 0.2. Furthermore, when the rubber yield increases are compared for the first and second half of 1982, guayule appears to be more sensitive to water stress in the latter rather than the first half of the year. This is shown by the significantly steeper slopes for the relative yield increase equations versus 2; SDD and mean CWSI for the harvest periods of 15 July 1982 to 15 January 1983 compared with the 15 December 1981 to 15 July 1982 (Figs. 4 and 5). The main reason for the increased sensitivity to plant water stress in the last half o f the year may be caused by the larger rate of biomass increase which occurs during late summer and early fall period. Higher air temperatures in late summer may also

101 IRRIGATION

<

TREATMENT

o , l I WET

O ' Z 3 MEDIUM

A'ZsDRY

e . Z 2 WET

I='r 4 MEDIUM

•=Z 6 DRY

1.0 .

.

.

.

~ ,of~,

.

.

,

,o

08

~ 06

0.6 JUL 15,t982 0.4

w

RYI'OT6"4.0xlO "4

SU~MER/F~-.L

.

.

.

JAN IS, LR83

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~"$DD

~ 06

°

', ~ 0

•

R 2 , 0 B8

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•

02

02

i

,

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i =

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oI

-600 - 4 0 0 "ZOO 0 +200 +400 CUMULATIVE STRESS DEGREE D A Y S

.J

.

~OS

,

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,

,

\

~

-600 -400 "200 0 +200 +400 CUMULATIVESTRESS DEGREE DAYS

( ~.SDO):C

I 0~

=

i

=

i

-i200 - 8 0 0 - 4 0 0 0 "(-400 +BOO CUMULATIVE STRESS DEGREE DAYS

( ZSDO),'C

( ZSOD),'C

Fig. 4. Relative rubber yield increase versus cumulative stress degree days for three guayule cultivars under six irrigation treatments for specified harvest periods at Mesa, AZ, 1982. IRRIGATION TREATMENT: o - I " I WET o . l r S MEDIUM

-Z

e. Z z WET o , ,

LO

• . ' t 4 MEDIUM , I0

-o

• 1"5

DRY

• " 1"6

DRY

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I(

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SEASI~IAL DEC

a

•

,.J.£3 0 ~

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>~

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[]

JAN IS. 19S3 "

R2,081

• •

RYI =t IR- I OZ C"W~I

,

oz~

0.2

,,=, o z

>= o~

SUMMER/FALL JUL tTS(~Ig82

< 06

DEC i5,1981 TO IS, I H Z

.J o!2

o'.4

0'6

o!o

,o

MEAN CROP WATER STRESS INDEX {CWSl)

Do

o!z

o.'4 o16 o~8

MEAN CROP WATER STRESS INDEX {CWSI)

,o o

0'.2 o'.4 o'6 o's MEAN CROP WATER STRESS INOEX (c-~'~)

Fig. 5. Relative rubber yield increase versus mean crop water stress index for three guayule cultivars under six irrigation treatments for specified harvest periods at Mesa, AZ, 1982.

contribute to greater yield reductions due to water stress in the last half of a calender year. By averaging the CWSI over the entire growing season rather than only during the active growing season (estimated at mid-March to mid-October), we were able to obtain a higher correlation coefficient with respect to rubber yield than reported in the previous paper by Nakayama and Bucks (1984). SUMMARY AND CONCLUSIONS

Results from 2 years of guayule research at Mesa, AZ, using three cultivars and six irrigation treatments showed that dry matter, resin and rubber

102 yields can be linearly related to the cumulative evapotranspiration. To obtain high resin and rubber production within a short time, a high rate of water application will be required. These relationships also indicated that as much as 64% dry matter, 69% resin, and 65% rubber yield would be expected from clipped compared with wholeplant harvesting of plants within the first 2 years of growth. Also, guayule plants that are less than 2 years could be predicted to p r o d u c e 50% more resin than rubber. Water-use efficiencies ranging from 0.70 to 0.85 kg/m 3 for dry matter, 0.045 to 0.055 kg/m 3 for resin, and 0.030 to 0.040 kg/m 3 for rubber production based on the evapotranspiration of the guayule crop were obtained for the cultivars used. Yield and crop water stress relationships indicated that guayule grown in an arid environment can be more sensitive to water stress which occurs in the latter than the earlier half of a year. Stress degree days and crop water stress indices both showed similar responses in plant behavior. Drought tolerance can permit flexibility in irrigation scheduling; however, supplemental water must be applied at high rates in order to increase yield and shorten the growth cycle.

REFERENCES Bonner, J., 1975. Physiology and chemistry of guayule. In: W.G. McGinnies and E.F. Haase (Editors), A n International Conference on the Utilization of Guayule. Office of Arid Lands Studies, University of Arizona, Tucson, AZ, pp. 78--83. Bucks, D.A., Nakayama, F.S., French, O.F., Legard, W.W. and Alexander, W.L., 1985a. Irrigated guayule -- evapotranspiration and plant water stress. Agric. Water Manage., 10: 61--79. Bucks, D.A., Nakayarna, F.S., French, O.F., Rasnick, B.A. and Alexander, W.L., 1985b. Irrigated guayule -- plant growth and production. Agric. Water Manage, 10: 81-93. Doorenbos, J. and Kassan, A.H., 1979. Yield response to water. Irrig. Drain. Pap. 33, Food and Agricultural Organization, Rome, 193 pp. Foster, K.E., Taylor, J.G. and Mills, J.L., 1979. A sociotechnical survey of guayule rubber commercialization: a state-of-the-art report for the National Science Foundation Division of Policy Research and Analysis. Grant No. P R A 78-11632, Office of Arid Lands Studies, University of Arizona, Tucson, AZ, and Midwest Research Institute, Kansas City, M O , 433 pp. H a m m o n d , B.C. and Polhamus, L.G., 1965. Research on guayule (Parthenium argentatum) 1942--1959. U.S. Dep. Agric. Tech, Bull. 1327, 157 pp. Nakayama, F.S. and Bucks, D.A., 1984. Crop water stress index, soil water, and rubber yield relations for the guayule plant. Agron. J., 76: 791--794. National Academy of Sciences, 1977. Guayule: an alternative source of natural rubber. Washington, DC, 80 pp. Pinter, P.J., Jr., Fry, K.E., Guinn, G. and Mauney, J.R., 1983. Infrared thermometry: A remote sensing technique for predicting yield in water-stressed cotton. Agric. Water Manage., 6 : 385--395. Retzer, J.L. and Mogen, C.A., 1947. Soil--guayule relationships. J. Am. Soc. Agron., 49: 483--512.