Yield and Quality of Trickle Irrigated Chile

Agricultural Experiment Station • Bulletin 703

College of Agriculture, Consumer and Environmental Sciences New Mexico State University

March 1983


SUMMARY

The yield of trickle-irrigated green and red chile was found to increase with the amount of irrigation water applied, with maximum yield obtained for the treatment that received 20% more than the control treatment in 1980 and in 1981. Yields started to decrease in 1980 and 1981 for treatments which received 40% more water than the control treatment. The amount of water needed for trickle irrigated chile depends on many factors and varies from year to year. However, it appears from this study that between 90 and 95 cm (including 10 to 13 cm of rain) of water are required for maximum green chile yields, while slightly less water appears to be necessary for red chile. The effect of water treatments on chile quality were not clearly defined. Less than optimum water supplies appeared to favor more pungent chile, while in 1981 the second harvest chile was much more pungent than the chile harvested one month earlier. Lack of water also reduced the length and the weight of the chile pods.

CONTENTS


ACKNOWLEDGMENTS

This is a report of work done under a project funded by the Interstate Stream Commission through the New Mexico Water Resources Research Institute.


Yield and Quality of Trickle Irrigated Chile

P.J.Wierenga, Professor of Soil Physics, Department of Crop and Soil Sciences, New Mexico State University Las Cruces, NM 88003.

INTRODUCTION

Water requirements of chile peppers (Capsicum annuum L.) have received little attention in the United States. Although some studies have shown the physiological response of pepper plants to water stress (Gardner and Nieman, 1962; Gee et al., 1973; Meiri and Shalhevet, 1973, Beese et al., 1982) data on the relationship between water use and yield of chile peppers are scarce, especially with respect to trickle irrigation.

Results on bell peppers reported by Goldberg et al. (1976) indicate that high soil water potentials equivalent to relatively moist soil conditions were desirable for high pod yields at harvest. Beese et al. (1982) found that limiting the water applied to trickle-irrigated chile during the period of rapid vegetative growth reduced final yield. Their data indicated that the yield of chile was very sensitive to irrigation management. In New Mexico, few data are available on the effects of water management on yield and quality of chile peppers, and there is no information on the effect of trickle irrigation on the yields of chile peppers (Cotter, 1980).

Many studies have been conducted to show the relationship between crop yields and evapotranspiration, consumptive use or total water applied (Stewart et al., 1973, 1974; Hanks et al., 1978, Hagan and Stewart, 1972). These studies generally show that total dry matter production and/or yield of harvestable product are related to evapotranspiration.

The objectives of this study were to determine the effects of trickle irrigation on yield and quality of chile peppers in New Mexico and thus the potential for trickle-irrigated chile in New Mexico, and to evaluate the dependence of chile pepper yield on the amount of irrigation water applied.


METHODS AND MATERIALS

The study was conducted on a 3-ha field at the Plant Science Research Center of New Mexico State University.The center is located about eight miles southwest of Las Cruces, New Mexico, near the Rio Grande (Al-Khafaf et al., 1978). The field was divided in two sections, one of 2 ha and one of 1 ha. Chile was grown on the 2-ha field in 1977, 1978 and 1980 and on the 1-ha field in 1979 and 1981. The soil at the experimental site is a Glendale clay loam (mixed calcareous thermic family of typic Torrifluvent) (Beese et al., 1982). Experimental procedures were slightly modified over the years, but not to the extent that it invalidated year to year comparisons. The experimental site was arranged in a randomized complete block design with each plot having eight rows in 1977 and 1978, six rows in 1979 and four rows in 1980 and 1981. The rows were 1 meter (71 cm in 1979) apart and 100 meters long. The plots were irrigated with trickle lines (Bi-Wall II Irrigation Tubing, Reed Irrigation Systems, California in 1977 and 1978; Chapin Twin Wall, Watermatics, Watertown, N.Y. in 1979, 1980, 1981) connected to header lines which ran through the center of the field. The trickle lines were placed 5 cm below the surface of each row. The emitter spacing was 30 cm. Water with an average electrical conductivity of 1.24 mmhos/cm (Wierenga, 1977) was supplied from a nearby irrigation well.

Cultural practices consisted of plowing, disking and preparation of the beds. Following installation of the trickle tubing the field was planted with chile pepper (Capsicum annuum L. var New Mexico 6-4). Planting dates varied from year to year and are listed in table 1. The amount of seed used varied from 5 to 10kg/ha. In 1980 and 1981, Furadan was applied during planting at a rate of 10 kg/ha. Fertilizer application rates varied somewhat from year to year. In all years, except 1981 when no phosphorus was used, phosphorus was applied by sidedressing at a rate of 280 kg/ha of P2O5. Nitrogen application rates varied between 100 and 200 kg of N per ha. Nitrogen was applied by injecting urea (30 N) directly into the main header line.

Climate data were measured at a weather station adjacent to the field.

Irrigations were scheduled on the basis of soil-water potential measurements in 1977 and 1978, using tensiometers. In the following years, irrigations were scheduled on the basis of pan evaporation. During 1977 and 1978, the control plots were irrigated when the soil-water tension 20 cm below the trickle lines reached 0.25 bars. Treatments in 1977 received 60, 70 and 80 percent of water applied to the control plots. In 1978, treatments received 80, 120 and 140 percent of the water applied to the control plots. After 1978, the amount of water applied to the control plots was determined from pan evaporation data using an empirically determined pan factor, which was a function of the leaf area index (see figure 1). For a given leaf area index, the treatments received 80, 120 and 140 percent of the water applied to the control plots in 1979 and 1980, and 60, 80, 120 and 140 percent of the water applied to the control plots in 1981. Differential treatments were started on June 19, 1979, June 16, 1980 and June 14, 1981. Before the start of treatments, plots were generally irrigated once a week. After treatments were started plots were irrigated three times per week in the years 1979-1981 There were six replications in 1977, five replications in 1978, 1979 and 1980 and four replications per treatment in 1981.

chart illustrating Ratios of evapotranspiration to measured pan evaporation as a function of leaf area index

Fig. 1. Ratios of evapotranspiration to measured pan evaporation as a function of leaf area index

Sections of all plots were harvested to determine green and red chile yields each year. In 1977 and 1978, the area of land harvested was 24.8 m2 per plot and in 1979 it was 8.4 m2 per plot. In 1980 and 1981, it was 24.8 m2 per plot for green chile and 12.4 m2 per plot for red chile. Only the two center rows in each plot were harvested. Harvest dates for green and red chile are listed in table 1. In 1980 and 1981, the chile was analyzed for size, pungency and color. A subsample of 50 chile pods was taken from the chile pods harvested from each plot. The average pod weight was determined for each plot by weighing the subsample and dividing by fifty. The average pod length was determined by measuring the length of each of the 50 pods in the subsample and determining the average length. The pungency of the green chile and the color intensity of the red chile were determined by a commercial laboratory (CAL-COMPACK Foods, Inc., Anaheim, California). High pressure liquid chromatography and spectrofluorometric detection techniques were used for the pungency analysis (Woodbury, 1980).

Table 1. Planting and harvesting dates


Year Planting Date Green Chile Harvest Red Chile Harvest

l977 April 4 August 22 October 6
1978 March 17 August 17 November 15
1979 March 23 August 19 November 1
1980 March 25 September 2 October 31
1981 March 19 August 13 October 17
September 14

RESULTS AND DISCUSSION

Yields of Green and Red Chile

Table 2 shows the yield of green chile for the years 1977 to 1981. In 1981, the plots were harvested twice, and the yield data represent the combined yields from the two harvest periods. In all other years, the plots were harvested only once. The data in table 2 show a strong increase in yield with years. This increase is a result of at least two factors. First, the higher yields are a result of greater amounts of water used for irrigation in the latter years. In 1977 and 1978, the control treatments were irrigated when the soil-water tension at 20 cm below the trickle lines reached 0.25 bars. It appears from the data in table 2, and from detailed tensiometer measurements made during the 1981 season, that a soil water tension of 0.25 bars at 20 cm is too high for chile on the clay loam soil at the experimental site, and that irrigation at this tension leads to insufficient water being applied. In 1979, 1980 and 1981, the standard evaporation pan was used to schedule irrigations, and greater amounts of water were applied resulting in improved yields.


Table 2. Green chile yields1 as influenced by irrigation treatment

Year Treatment Water Applied2 Yield3 C.V.


% of control cm tons/ha %

1977 60 35.2 2.5c 36.0

70 37.2 3.7bc 36.0

80 39.5 5.6b 20.0

100 45.1 11.8a 20.3

1978 80 38.1 11.0d 5.2

100 44.2 14.2c 8.7

120 50.3 16.3b 11.1

140 56.4 19.1a 6.7

1979 80 53.1 13.0b 30.9

100 57.9 18.8ab 26.5

120 63.0 l8.1ab 12.5

140 65.0 22.8a 40.7

1980 80 62.1 18.8b 12.3

100 70.1 28.1a 5.4

120 79.9 30.2a 14.8

140 88.6 28.9a 12.2

1981 60 66.3 7.8c 27.7

80 75.9 24.6b 6.1

100 86.1 33.2a 11.8

120 93.6 37.2a 15.6

140 109.0 33.6a 10.7

1The 1981 yields include yields from the first harvest on August 13 and from the second harvest on September 13. The 100% treatments are the control treatments.

2Includes 10.3 rain in 1977, 3.6 cm rain in 1978, 14.3 cm rain in 1979, 9.8 cm rain in 1980 and 12.8 cm rain in 1981.
3Average yields, within years, having the same letter are not significantly different at the 5% level of probability.

For the years 1977 through 1979, the green chile yields increased with greater amounts of water applied for all treatments. However, in both 1980 and 1981, yields started to decrease for the 140% treatments. Maximum green chile yields were obtained during these latter two years for the 120% treatment. The l00%, or control treatment in 1980 and 1981, was based on pan evaporation data. Because the highest yields were obtained with the 120% treatment, and not with the control treatment, it is clear that the crop water needs of the control treatment were somewhat underestimated. On the other hand, applying 40% more water than to the control clearly reduced the yields in 1980 and 1981. Shmueli and Goldberg (1972) obtained maximum pepper yields when irrigation was at a rate equal to 1.3 times Class A pan evaporation. When more water was applied than 1.3 times Class A pan evaporation to the trickle irrigated chile, yields started to decrease.

The amount of irrigation water needed during any given year for trickle irrigated chile depends on the weather, the stand, the canopy development of the chile, the length of the growing season, the fertilizers used, the insect and disease problems and the yield one wants to obtain. As such, it is difficult to define the irrigation requirements of trickle irrigated chile. In figure 2, the green chile yields were plotted versus total amounts of water applied. Although the data vary considerably from year to year, it appears that between 90 and 95 cm (including 10 to 13 cm total rainfall) of water are required for maximum yields.

chart illustrating yield of green chile versus water applied (rainfall included) for the years 1977-1981

Fig. 2. Yield of green chile versus water applied (rainfall included) for the years 1977-1981

Table 3 shows the red chile yields for the years 1977 through 1981. As was the case for green chile, red chile yields also increased with greater amounts of water applied. However, the trend is not as clear as for the green chile yields. Red chile harvests in 1977, 1978 and 1979, included some nonmarketable chile, while in 1980 and 1981, only the marketable chile was harvested. Secondly, a virus infestation affected red chile yield in 1981, reducing yields as compared to the two previous years. Furthermore, it is possible that red chile yields are less affected by water treatments than green chile yields. Studies now underway are directed at investigating the effects of inducing stress conditions at various stages of the growth cycle. They should help in determining the effects of water treatments on yields of green and red chile. In figure 3, the yield of red chile is plotted versus irrigation water applied. The data show a fairly wide scatter which may be a result of the different management and harvest procedures used during the five year study, and of the different climatological conditions. In particular, the yield data before 1980 may be too high as a result of the inclusion of some nonmarketable chile in the yield data. Nevertheless, there is a clear trend in the yield data indicating higher yields with more water applied until about 60-70 cm of irrigation water, beyond which yield increases in red chile are much smaller or nonexistent.

Table 3. Red chile yields1 as influenced by irrigation treatment.
All yields were adjusted to eight percent water content.

Year Treatment Water Applied2 Yield3 C.V.


% of control cm tons/ha %

1977 60 30.2 0.84c 35.4

70 33.0 1.29bc 25.2

80 36.1 1.78 b 16.6

100 43.4 3.34a 22.1

1978 80 41.7 4.36a 11.9

100 49.5 4.80a 20.7

120 57.4 5.21a 12.8

140 65.3 5.36a 13.1

1979 80 45.2 4.41b 22.9

100 52.8 5.54ab 19.1

120 59.4 5.61ab 25.8

140 66.3 6.43a 23.7

1980 80 58.4 4.60a 7.2

100 67.8 5.36a 7.7

120 80.8 5.77a 11.3

140 90.9 5.49a 12.9

1981 60 56.6 2.69c 6.2

80 66.9 4.58b 5.9

100 77.9 4.92b 5.2

120 86.5 5.34a 6.8

140 98.6 4.86b 3.7

1The l00% treatments are the control treatments.
2Does not included 17 cm rain in 1977, l3.5 cm rain in 1978, 13.5 cm rain in 1979, 18.5 cm rain in 1980 and 12.8 cm in 1981.
3Average yields, within years, having the same letter are not significantly different at the 5% level of probability.

chart illustrating the ield of red chile versus water applied (excluding rain) for the years 1977-1981

Fig. 3. Yield of red chile versus water applied (excluding rain) for the years 1977-1981.

Table 4 presents the yields of red chile from plot areas harvested previously for green chile. Yields for red after green were not determined for 1977, 1978 and 1979. In both 1980 and 1981, yields for red after green were rather high compared with farm yields. The higher yields were obtained in 1981 which averaged 2,302 kg/ha, compared with 1,592 kg/ha in 1980, a difference of about 700 kg/ha. In contrast, red chile yields were higher in 1980 by about 400 kg/ha as compared to 1981.

Pungency, Color and Size

Pungency: Table 5 presents data on the pungency (expressed in heat units) of green chile for 1980 and 1981. In 1980 treatments had a significant effect on the pungency, resulting in more pungent chile for the drier treatments. The effect of water treatments on pungency was less clear in 1981, although the driest treatment again tended to produce the more pungent chile. More observations are necessary to determine whether there is a clear effect of irrigation management on pungency.


Table 4. Red after green chile yields1 as influenced by irrigation treatment.
All yields were adjusted to eight percent water content.

Year Treatment Water Applied2 Yield3 C.V.


% of control cm tons/ha %

1980 80 58.4 l.58a 11.3

100 67.8 1.34a 30.7

120 80.8 1.74a 27.3

140 90.9 l.72a 16.5

1981 60 56.6 2.51a 6.9

80 66.9 2.32a 6.5

100 77.9 2.11a 4.1

120 86.5 2.18a 12.0

140 98.6 2.38a 13.1

1The 100% treatments are the control treatments.
2Does not include 18.5 cm rain in 1980 and 12.8 cm rain in 1981.
3Average yields, within years, having the same letter are not significantly different at the 5% level of probability.

Table 5. Pungency, in heat units (1 heat unit is 1000 Scoville), for green chile harvested September 2, 1980, August 13, 1981 and September 13, 19811.

Year Treatment Water Applied2 Pungency3 C.V.


% of control cm heat units %
1980 80 62.1 l.33a 31.4

100 70.1 l.33a 16.8

120 79.9 0.68b 33.0

140 88.6 0.90ab 22.2

1st harvest-August 13, 1981 60 53.6 1.20a 39.0

80 61.0 0.85a 41.1

100 67.3 0.83a 40.1

120 72.4 0.94a 28.5

140 80.0 0.75a 42.6

2nd harvest-September 13, 1981 60 66.3 2.55a 18.3

80 75.9 2.25a 20.0

100 86.1 2.43a 30.1

120 93.6 2.60a 55.6

140 109.0 1.85a 34.9

1Analysis performed by CAL-COMPACK Foods, Inc., Anaheim, Cal. The more pungent chile has the higher heat unit.
2Includes 9.8 cm rain in 1980, 8.6 cm rain By August 13, 1981 and 12.8 cm rain by September 13,1981.
3Average heat units, within years, having the same letter are not significantly different at the 5% level of probability.

Quagliotti (1971) also observed increases in pungency from water stress, while Nour and Jones (1960) reported no effect of irrigation treatments on pungency, as measured by the length of the vein where the pungency is most concentrated. The data in table 5 clearly showed that for 1981 the chile harvested in September was much more pungent than the chile harvested in August, e.g. 0.91 heat units versus 2.33 heat units for the September harvest.

Color: Table 6 lists the color of the red chile harvested in 1981. Highest color was obtained for the 60% treatment and lowest color for the 120% treatment. Apparently, water stress increases the color intensity of the red chile. This suggests that, to obtain chile with high color, rates of water application should be reduced near the end of the growing season. This agrees with Palevitch et al. (1975) who reported increased paprika pigment yields by "early" termination of irrigation (see also Cotter, 1980). Too much stress throughout the growing season, however, reduces red chile yields (table 3), which is undesirable. Additional studies are needed to more precisely determine the effects of water treatments on color content of trickle irrigated chile. In particular, the effects of stress applied at various stages during the growing period on pungency and color content should be investigated.

Table 6. ASTA color1 for red chile in 1981, and average pod weight and pod length of green chile in 1980 and 19812.

Year Treatment Color Pod Weight Pod Length


% of control ASTA g/pod cm/pod

1980 80 -- 43.9c 12.2c

100 -- 49.0b 13.2b

120 -- 54.la 13.5a

140 -- 53.9a l3.5a

1981 60 l36a 38.0b 11.8b

80 133ab 47.7a 13.5a

100 122bc 50.5a 13.9a

120 114c 52.4a 14.1a

140 120c 55.5a 13.7a

1Higher ASTA color numbers refer to more intense red color.
2Average values having the same letter are not significantly different at the 5% level of probability.
Pod weight and pod length: The average pod weights and pod lengths for the green chile harvested in 1980 and 1981 are listed in table 6. In both years, pod weights and pod lengths increased with amount of water applied up to the 120% treatment but decreased (except for the 1981 pod weight) for the 140% treatment. Except for the 1981 pod weights, highest weights and lengths were obtained for the 120% treatment. Thus, too little and too much water not only decreases the yield but also decreases the size and weight of the individual pods.

REFERENCES

  1. Al-Khafaf, S., P. J. Wierenga and B. C. Williams. 1978. Evaporative flux from irrigated cotton as related to leaf area index, soil water and evaporative demand. Agron. J. 20:912-917.
  2. Beese, F., R. Horton, and P. J. Wierenga. 1982. Physiological response of chile pepper to trickle irrigation. Agron. J. 74:551-555.
  3. Cotter, D. J. 1980. A review of studies on chile. N. Mex. Agri. Exp. Sta. Bull. 673 pp. 29.
  4. Gardner, W. R. and R. H. Nieman. 1962. Lower limit of water availability to plants. Science 143:1460-1462.
  5. Gee, G. W., W. Liu, H. Olvang, and B. E. James. 1973. Measurement and control of water potential in a soil-plant system. Soil Sci. 115:336-342.
  6. Goldberg, D., B. Gornat, and D. Rimon. 1976. Drip irrigation: Principles, design and agricultural practices. Drip Irrig. Scientific Publ. Kfar Shmaryahu, Israel.
  7. Hagan, R. M. and 3. Stewart. 1972. Water deficits-irrigation design and programming. J. Irr. Drain. Div., Amer. Soc. Civil Eng. 98:215-237.
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  9. Meiri, A. and J. Shalhevit. 1973. Pepper plant response to irrigation water quality and timing of leaching. In: Physical Aspects of Soil Water and Salts in Ecosystems (A. Hadas et al. Ed.) Ecological Studies. Vol. 4.
  10. Nour, M. and H. B. Jones. 1960. Irrigation and fertilization of chile. N. Mex. Agri. Expt. Sta. Res. Rpt. 47.
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  12. Quagliotti, L. 1971. Effects of soil moisture and nitrogen level on the pungency of berries of Capsicum annuum L., Hort. Res. 2:93-97.
  13. Shmueli, M. and D. Goldberg. 1972. Response of trickle-irrigated pepper in an arid zone to various water regimes. Hort Science 13:241-243.
  14. Stewart, J. I., R. M. Hagan, and W. O. Pruitt. 1974. Functions to predict optimal irrigation programs. J. Irr. Drain Div., Amer. Soc. Civil Eng. 100:179-199.
  15. Stewart, J. I., R. M. Hagan, W. O Pruitt, and W. A. Hall. 1973. Water production functions and irrigation programming for greater economy in project and irrigation system design and for increased efficiency in water use. Final Report U.S. Dept. of Int. Bureau of Reclamation No. 14-06 D-7329. 161 pp.
  16. Stewart, J. I., R. D. Misra, W. O. Pruitt, and R. M. Hagan. 1975. Irrigating corn and grain sorghum with a deficit water supply. Trans. Amer. Soc. Agr. Eng. 18:270-280.
  17. Wierenga, P. J. 1977. Influence of trickle irrigation and surface irrigation on return flow quality. U.S. Environmental Protection Agency, Ada, Oklahoma. EPA-600/2-77/093.
  18. Woodbury, J. E. 1980. Determination of capsicum pungency by high pressure liquid chromatography and spectrofluorometric detection. J. Assoc. Off. Anal. Chem. 63:556-558.

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