African Crop Science Journal African Crop Science Society ISSN: 1021-9730 EISSN: 2072-6589 Vol. 4, Num. 3, 1996, pp. 289-294

Taro yield and dry matter distribution under upland conditions in Puerto Rico

R. GOENAGA

USDA, ARS, Tropical Agriculture Research Station, P.O. Box 70, Mayaguez, Puerto Rico 00681

(Received 12 January, 1996; accepted 9 September, 1996)

Code Number: CS96068
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ABSTRACT

Yield performance of taro (Colocasia esculenta (L.) Schott), has received limited research attention, particularly under intensive cropping systems needed to meet demands of a growing population and supply corms for export markets. Four taro cultivars were evaluated for yield and dry matter distribution at two locations in Puerto Rico. Averaged across locations and cultivars, leaves, petioles, roots, corms, and suckers represented about 3%, 6%, 2%, 37%, and 52%, respectively, of the total plant dry matter. At both locations, cultivar Lila showed highest fresh corm yield (19,533 kg ha^-1), corm dry matter yield (6,648 kg ha^-1), and harvest index (0.49) among the cultivars studied. This formation is valuable for the development of an upland taro industry.

Key Words: Colocasia esculenta, corm yield

RESUME

La performance en rendement de taro (Colocasia esculenta (L.) Schott) a recu une attention limitee, en particulier dans les systemes de culture intensive qui ont pour but de satisfaire la demande en recolte d' une population croissante et de fournir des bulbes pour les marches etrangers. Quatre varietes de taro ont ete evaluees a deux endroits differents de Porto Rico pour examiner leur rendement et leur distribution en matiere seche. En moyenne, compte tenu des differences de sites et de varietes, les feuilles, les tiges, les racines, les bulbes et les surgeons representent respectivement 3%, 6%, 2%, 37%, et 52% du total de la matiere seche de la plante. A chaque endroit, la variete Lila a donne un rendement plus eleve en bulbes frais (19,533 kg par hectare), en matiere seche de bulbes (6,648 kg par hectare), et en indice de recolte (0.49), entre les varietes etudiees. Ce renseignement est utile pour le developpement de l'industrie du taro.

Mots Cles: Colocasia esculenta, rendement

INTRODUCTION

Taro (Colocasia esculenta (L.) Schott) is a staple root crop for inhabitants of the Caribbean Basin as well as Southeast Asia, India, Oceania, and West Africa (Goenaga et al., 1991). However, production of taro in the Caribbean Basin has been lagging behind that of other root and tuber crops (e.g., tanier, yam, and cassava), partly because it has received very little research attention.

Current yield levels in taro production are low. On a worldwide basis, the crop yields only about 6,000 kg ha^-1 compared with 14,746 kg ha^-1 for potato (Solanum tuberosum L.), and 13,628 kg ha^-1 for sweet potato (Ipomoea batatas L.) (F.A.O., 1992). In traditional farming situations in the tropics, taro is grown under rainfed conditions, which can lead to drastic yield declines after transient drought periods. In addition, yield potential of taro is seldom realised because of lack of knowledge concerning diseases and proper management practices, and scarcity of superior cultivars.

Research conducted in Hawaii and Puerto Rico (Silva et al., 1992; Goenaga and Chard—n, 1995) has demonstrated that, depending on plant density, taro is capable of yielding between 21,000 and 73,000 kg ha^-1 when grown under intensive commercial management. This illustrates that much of the potential for taro lies in commercial rather than subsistence production, particularly if the goal is to increase food production for the growing population in the tropics and for the establishment of export markets.

The objective of this study was to evaluate local and introduced taro cultivars grown under intensive management at two locations for yield and dry matter distribution. This study also forms part of an ongoing effort to validate the SUBSTOR-Aroids model developed to accelerate transfer of agrotechnologies for aroid production in the tropics (Goenaga et al., 1991; Singh et al., 1992).

MATERIALS AND METHODS

The study was conducted in Puerto Rico during 1993-94 at the USDA-ARS Research Farms in Mayaguez (Consumo clay, clayey, mixed, isohyperthermic Typic Haplohumults) and Isabela (Coto clay, clayey, kaolinitic isohyperthermic Typic Eutrustox). Taro suckers of local cultivars 'Blanca' and 'Lila' as well as the Hawaiian cultivars 'Lehua' and 'Niue' were planted on 14 September 1993 (Mayaguez) and 21 September 1993 (Isabela) in a randomised complete block design with five replications at each location. Within a replication, plots for each cultivar consisted of four rows of ten plants spaced 0.91 x 0.46 m apart. The experiment was surrounded by two rows of guard plants.

Relevant soil fertility data for both locations are given in Table 1. Weather data (Table 2) were collected throughout the experimental period using an automated weather station (LI-1200S, LI-COR1, Lincoln, NE).

At planting, each plant received 3.5 g of phosphorus provided as triple superphosphate. Plots were drip irrigated when the soil water tension, measured with tensiometers at a depth of 15 cm, exceeded 20 kPa. Throughout the nine-month experimental period, fertilizer was provided weekly through the drip system at the rate of 2.8 and 5.2 kg ha^-1 of N and K, respectively, using a mixture of potassium nitrate and urea as the nutrient sources.

Linear measurements of leaf blades were taken at 29, 69, 119, 149, 169, 203, and 230 days after planting to estimate leaf area index (LAI) of plants nondestructively (Goenaga and Singh, In Press). At harvest, leaves of plants were cut at the midrib-petiole intersection and brought to the laboratory for leaf area determination using a LI-COR 3000A area meter. Plants were then harvested by digging an area of 0.42 m^2 around each plant and to a depth of 30.5 cm. Plants were pulled from the soil, washed, and separated into petioles, corms, roots, and sucker components (cormels, leaves, petioles, and roots). Samples were dried to constant weight at 700C for dry matter determination. Harvest index (HI) was calculated as the ratio of corm dry weight to total dry matter yield.

Analysis of variance and best-fit curves were determined using the ANOVA and GLM procedures of the SAS program package (SAS Institute, 1987).

Table 1

Table 2

Table 3

Climatic conditions differed at the two locations. At Mayaguez, 54% of the total rain fell during the months of September and October, whereas rainfall at Isabela was more evenly distributed (Table 2). Average monthly solar radiation was 17% higher at Isabela than at Mayaguez, but maximum air temperature was higher at Mayaguez.

At harvest, total dry matter content did not differ significantly between locations and among cultivars; however, the location x cultivar interaction was highly significant (Table 3). Cultivars Lila and Lehua had higher dry matter content at Isabela, whereas cultivars Niue and Blanca had higher dry matter content at Mayaguez. Averaged across locations and cultivars, leaves represented about 3%; petioles 6%; roots 2%; corms 37%; and suckers, 52% of the total plant dry matter. However, cultivars varied significantly in their distribution of dry matter to plant parts (Table 3). Averaged across locations, cultivars Blanca, Lehua, and Niue allocated between 52% and 56% of their total dry matter to suckers and between 29% and 39% to edible corms. This was in contrast to cultivar Lila, which allocated 45% of its total dry matter to suckers and 49% to corms (Table 3).

It is noteworthy that the suckers (including nonsprouted cormels) were the predominant sink of dry matter in the plant. The partitioning of a significant percentage of dry matter to suckers and cormels is of particular importance because, when taro is grown under upland conditions, unsprouted cormels and corms of suckers seldom reach a marketable size and may compete for assimilates with the marketable main-plant corm. This situation contrasts greatly with that found in other root crops (e.g., sweet potato, cassava, and yam) in which photosynthate is translocated primarily to a single and dominant storage organ during the bulking period.

At harvest, leaves accounted for less than 2% of the total dry matter produced by each cultivar (Table 3). An exception was cultivar Blanca, which, at both locations, had significantly higher leaf dry matter content and LAI (Table 3). At Mayaguez, cultivars Blanca and Niue produced significantly higher petiole dry matter; whereas, at Isabela, production was similar among cultivars except for Lila, whose petiole dry matter was significantly lower.

Production of corm dry matter was significantly different among the cultivars (Table 3). A significant location x cultivar interaction indicated that production of corm dry matter varied with location. At Mayaguez, plants of cultivar Lila produced at least 43% more corm dry matter than those of the other cultivars. At Isabela, cultivars Lila and Lehua did not differ significantly in their production of corm dry matter, which was, on the average, 84% higher than that of Blanca and Niue (Table 3). Cultivar Lehua yielded 45% less corm dry matter at Mayaguez than at Isabela (Table 3). It is possible that, in contrast to the other cultivars used in this study, cultivar Lehua is less tolerant to high soil-moisture conditions and to the heavy soils found at Mayaguez. Therefore, the heavy rains that fell during September and October at Mayaguez (Table 2) may have created a soil environment that affected root respiration in plants of this cultivar. This, in turn, could have caused a decline in LAI (Fig. 1), less assimilate production and, therefore, the subsequent reduction in corm yield. A study by de la Pe–a and Melchor (1984) indicated that the chemical properties of water-saturated soils can cause a decline in corm yield.

Figure 1

There was no significant difference in fresh corm yield between locations. However, the effect of cultivar and the location x cultivar interaction were significant (Table 3). At both locations, cultivar Lila had higher fresh corm yield, indicating the superior performance of this cultivar. Although fresh corm yield at Mayaguez was similar for cultivars Blanca and Lila, their corm dry matter content differed as a result of a higher water content in Blanca corms (Table 3).

The results of this study demonstrated varietal differences in fresh and dry corm yields. This information is essential as an initial step in the development of a modern upland-taro industry that can meet the demand of the local population and supply future export markets in the Caribbean Basin. Information obtained is currently being used as part of a data base on taro for the validation of the SUBSTOR-Aroids model, which was developed to improve agrotechnology transfer of the crop.

ACKNOWLEDGMENTS

I thank Dr. Ramon de la Pena, University of Hawaii, for kindly providing the planting material for cultivars Lehua and Niue.

REFERENCES

de la Pena, R.S. and Melchor, F.M. 1984. Water use and efficiency in lowland taro production. In: Proceedings of the Sixth Symposium of the International Society for Tropical Root Crops. pp. 97-101. International Potato Center, Lima, Peru.

F.A.O. (Food and Agriculture Organization). 1992. Production Yearbook 45:67-184. Rome, Italy: FAO.

Goenaga, R., Singh, U., Beinroth, F.H. and Prasad, K. 1991. SUBSTOR-Aroid: A model in the making. Agrotechnology Transfer 14:1-4.

Goenaga, R. and Chardon, U. 1995. Growth, yield and nutrient uptake of taro grown under upland conditions. Journal of Plant Nutrition 18:1037-1048.

Goenaga, R. and Singh, U. Estimation of leaf area of taro (Colocasia esculenta (L.) Schott) from linear measurements. Journal of Agriculture of the University of Puerto Rico 80(3):In Press.

SAS Institute, Inc. 1978. SAS/STAT guide for personal computers. Cary, North Carolina.

Silva, J.A., Coltman, R., Paull, R. and Arakaki, A. 1992. Response of Chinese taro to nitrogen fertilization and plant population. In: Proceedings of the Workshop on Taro and Tanier Modeling. Singh, U. (Ed.), pp. 13-16. University of Hawaii, College of Tropical Agriculture and Human Resources, Honolulu, Hawaii.

Singh, U., Tsuji, G.Y., Goenaga, R. and Prasad, H.K. 1992. Modeling growth and development of taro and tanier. In: Proceedings of the Workshop on Taro and Tanier Modeling.

Singh, U. (Ed.), pp. 45-56. University of Hawaii, College of Tropical Agriculture and Human Resources, Honolulu, Hawaii.

Copyright 1996 The African Crop Science Society

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