Crop Phenology for Irrigated Chiles (Capsicum annuum L.) in Arizona and New Mexico. Roberto Soto-Ortiz, Jeffrey C. Silvertooth, and Abraham Galadima, Department of Soil, Water and Environmental Science University of Arizona Abstract To determine growth and development patterns of irrigated green chile plants as a function of heat units accumulated after planting (HUAP), as well as to develop a general irrigated chile plant development model as a function of HUAP. Field experiments were conducted in 2004 and 20055 at Sunsites in Cochise County, AZ (about 4,000 ft. elevation) and at the Massey Farm in the Animas Valley, NM (about 4,392 ft. elevation). Basic plant growth and development measurements were collected routinely and important phenological stages that corresponded to first bloom, early bloom, peak bloom, physiological maturity, and red harvest were identified and recorded. Results indicate that among all sites, all varieties have performed similarly in relation to HU accumulation patterns and preliminary plant phenology models are under development in this program. The primary difference between sites was that at Sunsites varieties tend to reach a 50/50 (green: red chile) ratio at 2900 HUAP and for Animas valley; this same ratio was reached at 3200 HUAP. Also, a general irrigated green chile plant development model as a function of HUAP for all sites and varieties was obtained. The purpose of this phenological baseline or model is to assist growers in predicting and identifying critical stages of growth for crop management purposes. First bloom occurred at 1369 ± 72 HUAP, early bloom at 1667 ± 79 HUAP, peak bloom at 1998 ± 84 HUAP; physiological maturity at 2285 ± 159 HUAP, and red chile harvest was identified to occur at 3295 ± 216 HUAP.

Key Words: Chile, Capsicum annuum L., crop phenology, growth and development, heat units. Introduction Chiles (Capsicum annuum L.) remain a stable and important crop for several crop production areas in the desert Southwest chile belt (New Mexico, Arizona, Texas, and northern Chihuahua, Mexico). Chiles (green and red) in the Sulfur Springs Valley of Cochise County are primarily produced under center pivot irrigation. Chile jalapeños are produced in Pinal County in central Arizona.

______________________________________________________________________________ This is part of the University of Arizona College of Agriculture 2006 Vegetable Report, index at: http://cals.arizona.edu/pubs/crops/az1419/

Recent trends indicate that demands for crops such as chile peppers in the U.S.A. are increasing. As a result, an increase in cultivated chile acreage is needed to meet the market demands for this crop (Johnson and Decoteau, 1996; Johnson and Johnson, 1992).

The latest data from the USDA

Agricultural Statistics Service showed New Mexico (NM) to be the leading State in chile production in the U.S.A. where about 18,000 acres were committed to production in 2002. Planted acreage in Arizona (AZ) is estimated at 6,000 – 10,000 acres in the recent years. The acreage level has increased in AZ from about 4,000 acres that were reported for 1998. The increase in demand, coupled with more land being committed to chile production has created the need to enhance the basic understanding of chile crop agronomy and general production practices to improve efficiencies.

Accurate prediction of harvest date and developmental stages of a crop has widespread application for improving management of that crop (e.g. fertilization, irrigation, scheduling multiple harvests, pest management activities, labor and machinery, etc.). We often can monitor and predict development based on measuring the thermal conditions in the plant’s environment. Various forms of temperature measurements and units commonly referred to as heat units (HU) or growing degree units, have been utilized in numerous studies to predict phenological events for both agronomic and horticultural crops (Baker and Reddy, 2001).

Wurr et al. (2002) stated that to describe crop growth and development there is first the need to determine rate functions for various processes; these include the identification of distinct stages and phases of growth and development, as well as the prediction of duration of developmental phases for given temperature regimes. At present, there is very limited information available concerning basic crop growth and development for irrigated chiles in the desert southwest. Some relevant information does exist in the literature for chiles but it is very limited in scope and the work has dealt primarily with varieties and cultural practices that have changed considerably in recent years (Beese et al. 1982; and Horton et al. 1982). The literature regarding the basic agronomic aspects of chile production in Arizona is virtually nonexistent. Therefore, there is a distinct need to develop an understanding of basic crop phenology in the desert Southwest. Hence, the objectives of this study were: 1) to determine growth and development patterns of irrigated chile plants as a function of heat units accumulated after planting (HUAP), and 2) to develop a general irrigated green and red chile plant development model as a function of HUAP that could be extended as a crop management tool.

Materials and Methods

Field experiments were conducted in 2004 and 2005 at Curry Farms (Mr. Ed Curry, grower-cooperator) on a Borderline fine sandy loam (coarse-loamy, mixed, superactive thermic Typic Calcigypsids) near Sunsites in Cochise County, AZ (about 4,000 ft. elevation) and at the Massey Farm in the Animas Valley, NM (about 4,392 ft. elevation), to conduct phenological monitoring studies of chiles. The project involved the evaluation of a total of 10 Chile varieties being evaluated in the Sulfur Springs Valley of Arizona (near Sunsites, AZ) and the Animas Valley of New Mexico (near Animas, NM). The study areas were planted on 40 in. wide beds at Curry Farms in AZ and 30 in. beds at Massey Farms in NM. All inputs such as fertilizer, water, and pest control were managed on an as-needed basis by the growercooperators. Basic agronomic information for all sites is presented in Table 1.

Climatic conditions were monitored and recorded on a daily basis throughout the growing season using an Arizona Meteorological Network (AZMET) station sited near Sunsites, and a New Mexico Climate Station Data (NMCC) for the Animas Valley location. The weather stations near the experimental sites are automated and are used to determine the hourly (AZMET) and daily (NMCC) maximum and minimum temperature values. Consequently, the HU accumulations (86/55 oF thresholds) are calculated by a method presented in Baskerville and Emin (1969) and modified by Brown (1989). The daily HU accumulations are summed up from the time of planting and reported as HUAP.

In-season data collection for each field was taken from 2m row segments at five randomly selected locations in each field for the entire season and they included the following basic Plant growth and development measurements: number of mainstem nodes from cotyledons to crown formation, height of mainstem from cotyledons to the crown (cm), number of branches and height of each branch formed at the crown, total number of forks and pods formed on each branch, number of white flowers per branch, the number of nodes above the top white flower (NAWF), and above the newest pod position (NAPOD) for each branch. Also, on the red-type chile fields; percent green to red ratios were counted on 14 day intervals. This information provides crop maturity status and a means of comparing earliness or delayed maturities among varieties or cases under study. Plant measurements were made in regular 14-day intervals and the following growth stages were identified in each case: pre-bloom, early bloom, peak bloom (also corresponded to early pod development), and physiological maturity. Statistical analyses

were performed on all in-season data collected with statistical procedures consistent with those outlined by Steele and Torrie (1980) and SAS (SAS Institute, 199a and 1999b).

Results and Discussion Plant growth and development measurements. The 2005 in-season data for all varieties and all sites was collected and tabulated (Figures 1 - 5). In general, the in-season plant measurements provide an indication of the progression of vegetative/reproductive development of the plant along the fruiting cycle. Results indicate that for all site-years all varieties performed similarly in relation to HU accumulation patterns. As a result, preliminary plant phenology models under development in this program can be presented to the program community and given further testing and evaluation in commercial production setting. Further testing of this preliminary model is also continued objective of this research program.

Percent green to red ratio. As presented in Figures 6 and 7, all varieties demonstrated similar rates of transition from green to red chiles. The primary difference between sites was that at Sunsites varieties tend to reach a 50/50 ratio (red:green pods) at 2900 HUAP and for Animas valley; this same ratio was reached at 3200 HUAP. A general irrigated green chile plant development model as a function of HUAP for all sites and varieties is shown in Table 3. First bloom occurred at 1369 ± 72 HUAP, early bloom at 1667 ± 79 HUAP, peak bloom at 1998 ± 84 HUAP; physiological maturity at 2285 ± 159 HUAP, and red chile harvest was identified to occur at 3295 ± 216 HUAP.

Acknowledgements The authors appreciate the valuable support provided by the Fluid Fertilizer Foundation and the New Mexico Chile Task Force. Also, we are also very appreciative of the generous cooperation and support provided by the grower-cooperators at Curry Farms in Arizona and the Massey Farms in New Mexico. Also the hard work and technical assistance provided by the research assistants from the UA Agronomy program are greatly appreciated.

References Arizona Agricultural Statistics Service. 2002. United States Department of Agriculture. National Agricultural Statistics Service. Annual Statistics Bulletin. Baker, J.T., and V.R. Reddy. 2001. Temperature effects on phenological development and yield of muskmelon. Annals of Botany. 87:605-613. Baskerville, G.L. and P. Emin. 1969. Rapid estimation of heat accumulation from maximum and minimum temperatures. Ecology 50:514-517. Beese, F., R. Horton, and P.J. Wierenga. 1982. Growth and yield response of chile peppers to trickle irrigation. Agron. J. 74:556-561. Brown, P. W. 1989. Heat units. Ariz. Coop. Ext. Bull. 8915. Univ. of Arizona, Tucson, AZ. Johnson, C.D. and D.R. Decoteau. 1996. Nitrogen and Potassium Fertility Affects Jalapeño Pepper Plant Growth, Pod Yield, and Pungency. HortScience 31(7): 1119-1123. Johnson, J. and C. Johnson. 1992. Two zesty alternatives to bell peppers. Amer. Veg. Grow. May:2427. Horton, R., F. Beese, and P.J. Wierenga. 1982. Physiological response of chile peppers to trickle irrigation. Agron. J. 74:551-555. SAS Institute. 1999a. The SAS system for Windows. Version 8.0. SAS Inst., Cary, NC. SAS Institute. 1999b. SAS/STAT user’s guide. Version 8.0. SAS Inst., Cary, NC.

Steel, R.G.D. and J.H. Torrie. 1980. Principles and procedures of statistics. McGraw-Hill, New York. USDA. 2003. Soil Survey of Cochise County, Arizona. United States Department of Agriculture. Natural Resources Conservation Service-The Hereford, San Pedro, Willcox-San Simon, and Whitewater Draw Natural Resource Conservation Districts and the Arizona Agricultural Experiment Station. Wurr, D.C.E., J.R. Fellows., and K. Phelps. 2002. Crop Scheduling and prediction – Principles and opportunities with field vegetables. In: Advances in Agronomy. D.L. Sparks (Editor). Volume 76. Academic Press. p.p. 201-234.

Table 1. Basic agronomic information for chile experiments; Sunsites, AZ and Animas Valley, NM, 2004-2005. Site

Sunsites

Animas Valley

Variety

Wet Date

AZ 20 AZ 8 AZ 8 AZ 21 AZ 335-270 Esquina Ancho X Chile AZ 20

3/23/04 3/23/04 4/12/05 4/25/05 4/25/05 4/01/05 3/14/05 3/25/05

Grande B58 300 LB 25

4/04/05 4/07/05 4/07/05 4/07/05

Irrigation Type

Soil Type

Sprinkler

Drip

Fine sandy loam1 [coarse-loamy, mixed, superactive thermic Typic Calcigypsids]

Sprinkler

1] USDA. (2003).

Table 2. Sampling dates for chile experiments; Sunsites, AZ and Animas Valley, NM, 2004-2005. Site

Variety

AZ 8 AZ 20 Sunsites AZ 8 AZ 21 AZ 335-270 Esquina Ancho X Chile AZ 20

Animas Valley

Grande B58 300 LB 25

First Bloom

Early Bloom

Peak Bloom

Physiological maturity

6/23/04 6/23/04 6/08/05 6/23/05 6/23/05 6/08/05 6/08/05 6/08/05

7/13/04 7/13/04 6/23/05 7/06/05 7/06/05 6/23/05 6/23/05 6/23/05

7/29/04 7/29/04 7/20/05 7/20/05 7/20/05 7/20/05 7/20/05 7/20/05

8/31/04 8/31/04 8/17/05 8/17/05 8/17/05 8/17/05 8/17/05 8/25/05

6/30/05 6/30/05 6/30/05 6/30/05

7/15/05 7/15/05 7/15/05 7/15/05

7/29/05 7/29/05 7/29/05 7/29/05

8/27/05 8/27/05 8/27/05 8/27/05

S u n s ite s 2 0 0 4 20

15

10 AZ 20 AZ8

5

0

AZ 20 A Z8

3

2

1

80

N um ber of pods

H e ig h t to c ro w n

20 AZ 20 A Z8

10

0 3 .2

AZ 20 AZ8

60

Number of pods

30

centimeters

N u m b e r o f f lo w e rs

4

Number of flowers

Number of nodes

N o d e s to c ro w n

40

20

0

B ra n c h e s a t c ro w n

B ra n c h h e ig h t

Number of branches

3 .0 60

centimeters

2 .8 2 .6 AZ 20 AZ8

2 .4 2 .2 2 .0

AZ 20 A Z8

40

20

1 .8 0 6

N u m b e r o f f o rk s

300

X D a ta

Number of nodes

Number of forks

1 .6

AZ 20 AZ8

200

100

0

N o d e s A b o v e w h ite f lo w e r

5 AZ 20 AZ8

4 3 2 1 0

500

1000

1500

2000

2500

o

H e a t U n its A c c u m u la te d A fte r P la n tin g (H U A P 8 6 /5 5 F )

500

1000

1500

2000

2500

o

H e a t U n its A c c u m u la te d A fte r P la n tin g (H U A P 8 6 /5 5 F )

F ig u re 1 . G ro w th a n d D e v e lo p m e n t v a ria b le s a s a f u n c tio n o f H U A P f o r a ll c h ile v a rie tie s . C u rry 's F a rm . S u n s ite s , A z . 2 0 0 4 .

S u n s ite s 2 0 0 5 20

15

10 AZ 20 AZ 21 A Z 3 3 5 -2 7 0 A Z8 ANCHO E S Q U IN A

5

0

centimeters

2

1

0

N um ber of pods

20 AZ 20 AZ 21 A Z 3 3 5 -2 7 0 AZ 8 ANCHO E S Q U IN A

10

0

AZ 20 AZ 21 A Z 3 3 5 -2 7 0 AZ 8 ANCHO E S Q U IN A

30

20

10

0

B ra n c h e s a t c ro w n

3 .0

Number of branches

AZ 20 AZ 21 A Z 3 3 5 -2 7 0 AZ 8 ANCHO E S Q U IN A

3

H e ig h t to c ro w n Number of pods

30

N u m b e r o f flo w e rs

4

Number of flowers

Number of nodes

N o d e s to c ro w n

B ra n c h h e ig h t centimeters

60 2 .5

2 .0 AZ 20 AZ 21 A Z 3 3 5 -2 7 0 AZ 8 ANCHO E S Q U IN A

1 .5

40

1 .0

0

N u m b e r o f fo rk s 150

100 AZ 20 AZ 21 A Z 3 3 5 -2 7 0 AZ 8 ANCHO E S Q U IN A

50

0 600

800

1000

1200

1400

N o d e s A b o v e w h ite flo w e r

6

X D a ta

1600

1800

2000

2200

o H e a t U n its A c c u m u la te d A fte r P la n tin g ( H U A P 8 6 /5 5 F )

Number of nodes

Number of forks

AZ 20 AZ 21 A Z 3 3 5 -2 7 0 AZ 8 ANCHO E S Q U IN A

20

AZ 20 AZ 21 A Z 3 3 5 -2 7 0 AZ 8 ANCHO E S Q U IN A

4

2

0 600

800

1000

1200

1400

1600

1800

2000

2200

o H e a t U n its A c c u m u la te d A fte r P la n tin g ( H U A P 8 6 /5 5 F )

F ig u re 2 . G ro w th a n d D e v e lo p m e n t v a ria b le s a s a fu n c tio n o f H U A P fo r a ll c h ile v a rie tie s . C u rry 's F a rm . S u n s ite s , A z . 2 0 0 5 .

Sunsites 2005 6

5

Nodes above newest pod

Vegetative branches Number of vegetative branches

Number of nodes

5 AZ 20 AZ 21 AZ 335-270 AZ 8 ANCHO ESQUINA

4

3

2

1

0

4

AZ 20 AZ 21 AZ 335-270 AZ 8 ANCHO ESQUINA

3

2

1

0 600

800

1000

1200

1400

1600

1800

2000

Heat Units Accumulated After Planting (HUAP 86/55oF)

2200

600

800

1000

1200

1400

1600

1800

2000 o

Heat Units After Planting (HUAP 86/55 F)

Figure 3. Growth and Development variables as a function of HUAP for all chile varieties. Curry's Farm. Sunsites, Az. 2005.

2200

A n im a s 2 0 0 5 20

10

N u m b e r o f f lo w e r s Number of flowers

Number of nodes

N o d e s to c r o w n 15

10 GRANDE B58 300 LB25

6 4 2 60

5

N um ber of pods

H e ig h t t o c r o w n

50

Number of pods

30

centimeters

GRANDE B -5 8 300 L B -2 5

8

20 GRANDE B -5 8 300 L B -2 5

10

0 3 .2

GRANDE B -5 8 300 L B -2 5

40 30 20 10 0

B ra n c h e s a t c ro w n

B r a n c h h e ig h t

Number of branches

60

centimeters

3 .0 2 .8 2 .6 GRANDE B -5 8 300 L B -2 5

2 .4 2 .2

40

GRANDE B -5 8 300 L B -2 5

20

2 .0

0 8

N o d e s A b o v e w h ite f lo w e r GRANDE B -5 8 300 L B -2 5

X D a ta

GRANDE B -5 8 300 L B -2 5

150

Number of nodes

Number of forks

N u m b e r o f fo rk s

100

50

0

6

4

2

0 1400

1600

1800

2000

2200

2400

2600

2800

o

H e a t U n its A c c u m u la te d A fte r P la n tin g ( H U A P 8 6 / 5 5 F )

1400

1600

1800

2000

2200

2400

2600

2800

o

H e a t U n its A c c u m u la te d A fte r P la n tin g ( H U A P 8 6 /5 5 F )

F ig u r e 4 . G r o w t h a n d D e v e lo p m e n t v a r ia b le s a s a f u n c t io n o f H U A P f o r a ll c h ile v a r ie t ie s . M a s s e y 's F a r m . A n im a s , N m . 2 0 0 5 .

Animas 2005

6

Number of nodes

5

Nodes above newest pod

Vegetative branches Number of vegetative branches

8

GRANDE B-58 300 LB-25

4

2

0

4

GRANDE B-58 300 LB-25

3

2

1

0 1400

1600

1800

2000

2200

2400

2600

Heat Units Accumulated After Planting (HUAP 86/55oF)

2800

1400

1600

1800

2000

2200

2400 o

Heat Units After Planting (HUAP 86/55 F)

Figure 4. Growth and Development variables as a function of HUAP for all chile varieties. Massey's Farm. Animas, Nm. 2005.

2600

2800

Sunsites 2005 100 AZ 335-270

% Green/Red

80

60

40

20 % Green % Red 0

Esquina

% Green/Red

80

60

40

20 % Green % Red 0 2200

2400

2600

2800

3000

Heat Units Accumulated After Planting (HUAP 86/55oF) Figure 5. Percent green to red ratio of AZ 335-270 and Esquina as a function of HUAP. Curry's Farm. Sunsites, Az. 2005.

Animas 2005 100

B-58

% Green/Red

80

60

40

20

% Green % Red

0

LB-25

% Green/Red

80

60

40

20

% Green % Red

0 100

300 % Green/Red

80

60

40

20

% Green % Red

0 2700

2800

2900

3000

3100

3200

3300

3400

Heat Units Accum ulated After Planting (HUAP 86/55 o F) Figure 7. Percent green to red ratio of B-58, LB-25 and 300 as a function of HUAP. Massey's Farm. Anim as, NM. 2005.

Table 3. Chiles phenological stages as a function of Heat units accumulated after planting (HUAP), Arizona. 2004-2005. HUAP (86/55 °F threshold). Site

Phenological Stage

Mean

Standard Deviation

Sunsites,

First Bloom Early Bloom Peak Bloom Physiological Maturity Red Harvest

1359 1616 1945 2213 3112

89 32 37 148 124

New Mexico.

First Bloom Early Bloom Peak Bloom Physiological Maturity Red Harvest

1388 1769 2104 2430 3416

10 9 9 9 172

Combined

First Bloom Early Bloom Peak Bloom Physiological Maturity Red Harvest

1369 1667 1998 2285 3295

72 79 84 159 216

Arizona.

Animas,Valley,