Evaluation of Agronomic Performance of Green Gram Accessions Grown under Reduced Light Intensity in the Arid and Semi-Arid Areas of Kenya

Green gram (Vigna radiata (L.) is the hardiest of all pulses and is well adapted to Arid and Semi-Arid Areas (ASALs). However, the high light intensities, temperatures and erratic rainfall experienced in these areas lead to high evapo-transpiration rates leaving very little water available for plant use, thus negatively affecting growth and yield parameters. This study was conducted to evaluate the effect of reduced light intensity on agronomic performance of four high yielding green gram accessions (GBK-022494A, GBK-022501A, GBK-022502A and Nylon-1). The study was carried out at Kiboko in Makueni County, Kenya during the 2012 short and 2013 long rain seasons. A Shade net used in this study reduces light intensity by 35 percent. The experiment was laid out in a split-plot arrangement with three replications. The main plot treatment was shading at two levels; shaded and non-shaded while the 4 accessions formed the sub-plots. Data on plant height, days to flowering, days to maturity, pods per plant, seeds per pod, weight of 100 seeds and seed yield was collected. Results indicated that during the short rain season, accessions had significant (P≤.01) differences in the number of pods per plant, seed weight and plant height. Accession GBK-022501A was the tallest (55.1 cm) while Nylon-1 was the shortest (44.4 cm); Nylon-1 had the least (12.4 g) seed yield while GBK-022501A had the highest (17.2 g) seed yield. Shading created significant (P<.05) differences in seeds obtained per pod where production under shade gave an average of 9 seeds per pod compared to each 8 seeds in the open sunlight condition during the short rain seasons. During 2013 rain season, shade had significant (P<.05) effect on plant height and pod length. Under shade net plant height was 54.7 cm while under control, open sunshine condition it was 50 cm. Pod length under shade was 7.7 cm while under control, it was 7.4 cm. Generally, agronomic performance of green gram was improved by shading during the short rains unlike the long rains where growing in the open sunshine condition led to more robust growth and yield. It is therefore recommended that growers incorporate shading in their green gram production during periods of high light intensity.