Effects Of Plant Support System And Intercropping With Long Bean (Vigna Sinensis) On Growth, Yield And Fruit Quality Of Red Dragon Fruit (Hylocereus Polyrhizus).

Climbing epiphytic cacti, particularly members of the genera Hylocereus known as pitaya or dragon fruit, have recently drawn much attention of growers worldwide because of their economic value as food products and also owing to their high nutritive and medicinal values. These cacti are branched climbers needing strong structures to ensure their vigorous growth and heavy fruit yield for maximum yield production. Various designs of structure have been used to provide such support. In addition, it normally takes 12 to 18 months for dragon fruit to bear fruits after planting. Thus, it would be useful if intercropping could be practiced during this juvenile period of dragon fruit. Therefore a study was conducted to determine the effects of using three plant support systems, the pole, T bar trellis and V shape on growth, yield and fruit quality of dragon fruit and to evaluate the use of long bean as an intercrop with dragon fruit. Red dragon fruit (Hylocereus polyrhizus) as the main crop and long bean (Vigna sinensis) as the intercrop were used in this study. Two experiments were conducted, one involving field planting of dragon fruit with the respective support systems intercropped with long bean while the other was conducted using box planting to evaluate root interaction between dragon fruit and long bean. In the first experiment, the support systems indicated significant effects during the reproductive stage of dragon fruit resulting in differences in total number of flower buds produced, percentage of flowers aborted, fruit number and total fruit weight. Dragon fruit plants using the pole system showed 17–38% more flower buds produced, 15–36% more fruits and 24% heavier total fruit weight compared to those of the T-bar trellis and V- shape systems, respectively. There were also significant effects of plant support systems on soluble solid concentration (% Brix) where T-bar trellis and pole systems showed 7% higher in the value of soluble solid concentration than the V-shape system. Intercropping had no influence in all the parameters measured. Support systems did not have any significant effect on the vegetative characteristics of dragon fruit plants, such as days to produce new shoot from planting, number of shoots produced per cutting, stem diameter of dragon fruit, total stem surface area, chlorophyll content of stem and length of branch. Support systems also showed no significant effects on fruit size and days to attain fruit maturity in dragon fruit, and in the yield of long bean (two cycles). Similarly, fruit quality including fruit pH, peel and pulp colour and titratable acidity were not affected by different support systems or intercropping. Intercropping of long bean with dragon fruit, however, increased the incidence of insect damage. Based on the cost of the support system and yield of fruit obtained, the most cost effective support system is the pole system, which had the highest potential for fruit yield to recover its higher initial cost of construction especially if cheaper construction materials were made available. Although the V-shaped and T-bar trellis support systems had lower cost of construction than the pole system, their lower fruit yield would not generate high farm income over a longer period. Besides the pole support system had the advantage of simpler construction design and easier weed control. Land equivalent ratio (LER) for intercropping was shown to be higher than monocropping as indicated by an LER value greater than 1. Relative value total (RVT) of the V-shape system was higher than those of pole and T-bar trellis systems. Intercropping of dragon fruit and long bean also resulted in higher profitability index compared to dragon fruit as a sole crop. In the second experiment, dragon fruit showed 87% greater root volume when grown with long bean with the presence of soil partition than when grown as a monocrop in boxes. This indicated that there was more competition for root space between the dragon fruit plants when they were grown as a monocrop than when they were intercropped with long bean. Dragon fruit roots grow laterally while those of long bean grow deeper with prominent tap root system. Dragon fruit planted with long bean with or without the soil partition had higher total root surface area compared with dragon fruit as a sole crop. Similar trend was detected in average root diameter of dragon fruit.

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