Weed suppression through physical methods in cultivation constitutes of many methods but this experiment focused on application of various mulches. Recently, herbicide-free weed control methods in the world are getting more attention due to environmental and ecological factors. Green pepper production requires good management practices in order to attain potential yields. Most of the known physical practices of weed control cause both positive and negative effects. Therefore, great attention should be paid when selecting the appropriate mulch with the aim of weed suppression in any specific cultivation. Three types of mulches were examined for weed control namely; black plastic mulch, transparent plastic mulch, straw mulch and bare soil as control during the 2015 short and long raining seasons in Busia County. In both seasons, the black plastic mulch treatment significantly (P<0.05) showed the lowest number of weed species (3) per m 2 quadrat while the control had the highest with a maximum of 8 and 7 during the long and short raining seasons respectively. The number of species reduced after four weeks from transplanting when the first sampling was carried out. The lowest weed vigor was exhibited in the plastic treatments for both seasons at 4, 6 and 8 weeks after transplanting. Control had the highest weed fresh biomass for both seasons at all the sampling stages with the highest observed during the short raining season with 1626 g/m 2 at 4 weeks after transplanting. This also translated to the highest weed dry biomass for both seasons in the control plots with the lowest recorded in the black plastic mulch. Out of several physical methods of weed control, mulching seems to be the most appropriate with the black plastic mulch being the best.

A field experiment was conducted at the Kenya Agricultural and Livestock Research Organization, Alupe Research Farm, Busia County for two cropping seasons during the year 2015 to determine the impact of row spacing and mulching materials on weed management of two green pepper varieties. The two varieties California Wonder and Yolo Wonder were sown in a randomized complete block design in factorial arrangements, comprising three-row spacing treatments and four mulching materials then replicated thrice. The row spacing were; 30, 40 and 50 cm whereas the mulching materials were; black plastic mulch, transparent plastic mulch, straw mulch and bare soil which was the control. Data collected was subjected to SAS statistical software for analysis and means separated using LSD at P≤0.05. Significant differences (p≤0.05) were observed between the treatment combination of mulch and row spacing in the fresh and dry weed biomass, weed species density per m 2 and the weed growth vigor. The highest fresh weed biomass (5008 g.m -2 ) was elicited by the control mulch treatment at the widest row spacing during the long rains season while the lowest (188 g.m -2 ) was observed in the black plastic mulch at the narrow row spacing of 30 cm. The weed species density was highest (7) in the control at 40 cm row spacing with the lowest elicited in the black plastic mulch at the 40 cm row spacing (1.7) during the short rain seasons. The weed growth vigor was highest in all the control mulch treatments at 30 cm row spacing while the lowest vigor was in the black plastic mulch which was closely followed by the transparent mulch at the various row spacings. The competitiveness of sweet pepper with weeds can be significantly enhanced by using black plastic as mulch under narrow row spacing with an optimum of 30 cm.