PERFORMANCE OF FIVE WINTER VEGETABLES UNDER DIFFERENT LIGHT CONDITIONS FOR AGROFORESTRY SYSTEMS

Abstract

The performance of five winter vegetables was evaluated under four different light levels i.e., 100, 75, 50 and 25 percent Photosynthetically Active Radiation (PAR) at the experimental farm of the Bangabandhu Sheikh Mujibur Rahman Agricultural University, Salna, Gazipur during November 1999 to March 2000. Different light levels i.e., 75, 50 and 25 percent PAR were attained by using nets of different pore sizes. Four winter vegetables i.e., cabbage, carrot, radish and tomato were grown as in individual experiments following the RCBD design and three varieties of eggplant i.e., Nayantara, Kajla and Uttara were grown separately in Split Plot Design. Plant height of all the five vegetables increased gradually with the decreased of light level and significantly the longest plant was found under 25 percent PAR level i.e. severe shade level. Other parameters of the tested vegetables varied differentially due to variation of light levels. In cabbage, outer leaf length increased gradually with the decreased of light levels. Outer leaf breadth and yield contributing characteristics of cabbage i.e. head length, head breadth and head fresh weight were increased progressively up to 50 percent reduction of light levels. Further reduction of light level, the above parameters were drastically decreased. Fresh and dry yield (ton/ha) of cabbage produced under 50 percent PAR level were numerically higher (29.98 and 1.90, respectively) than those of yields obtained under full sunlight (28.92 and 1.72, respectively) and 75 percent PAR (29.52 and 1.89, respectively). In carrot, two parameters, i.e. plant height and leaf length were increased with the decreased of light levels. But the other parameters showed the superior performances under 25 percent reduced light level (75% PAR) and the least performances under 25 percent PAR level. The highest yield (30.64 ton/ha) was found under 75 percent PAR (25% reduced light) which was even statistically higher than those of the yields obtained under full sunlight (100% PAR) and 50 percent PAR. In radish, leaf length and leaf breadth increased gradually with the decreased of light level. In case of number of leaves per plant and dry weight of leaves per plant, the best performances were observed under 75 percent PAR level (25% shade level) and the poorest performances were observed under 25 percent PAR level (75% shade level). The values of the yield contributing characteristics such as radish length and radish girth were found the highest under 75 percent PAR level. Similarly, significantly the highest fresh yield of radish was found under 75 percent PAR level. In tomato, some parameters such as number of primary branches, number of fruit per cluster, fruit diameter, fruit weight were decreased with the decreased of light levels, and other parameters such as number of leaves per plant, number of cluster per plant, number of fruit per plant and yield were increased up to 25 percent reduction of PAR level. Further reduction of PAR level, these parameters vi were decreased gradually. The total yield of tomato obtained under full sunlight (94.62 ton/ha), 25 percent reduced light (96.02 ton/ha) and 50 percent reduced light (87.70 ton/ha) did not vary significantly but yield obtained under 75 percent reduced light level decreased remarkably. Among three varieties of eggplant, primary branches of Nayantara and number of leaves per plant of all the varieties were the highest under 75 percent PAR level. Fruit length and number of fruits per plant of all the three varieties were higher under 100 percent PAR. Fruit diameter of Nayantara only and fruit weight of all the varieties were higher under 75 percent PAR level. Fruit diameter of other two varieties i.e. Kajla and Uttara were higher under 100 percent PAR. Yield (t/ha) of eggplant irrespective of varieties were the highest under 100 percent PAR. However, yields decreased gradually with decreased of light levels. Relationship between light and yields of the studied vegetables were estimated. In case of eggplant, linear relationship between fresh yield and percent PAR was found, whereas in case of cabbage, carrot, radish and tomato quadratic (polynomial) relationships were found. From the above studies, it may be stated that the performances of different winter vegetables under different light levels were different. But their degree of adaptability to the different light levels ie., ability to grow under shade levels in agroforestry system may be ranked as cabbage>carrot> tomato>radish>eggplant (Kajla/Nayantara>Uttara).