David L. Coffey and Jimmy R. Summerlin, Jr.

Bell pepper ‘Camelot’ cv. plants grown on metalized UV reflective silver colored plastic mulch yielded significantly fewer fruits, and subsequently, produced lower total marketable yields than plants grown on black or white colored plastic. Individual fruit size from plants grown among all plastic and bare ground treatments were no different. Plants grown on the silver mulch exhibited a chlorotic appearance during much of the hotter portion of the growing season.

Continued research involving plasticulture technology is being conducted at the University of Tennessee to determine means to increase the yield and quality of bell peppers. Higher yields of larger, better grade-out fruits than are currently achieved by most growers of bell peppers for the fresh market are needed for growers to maximize their returns from the production of this crop.

Field plots were established in a randomized complete block design with four replications. Mulches evaluated were the three plastic colors: black, white, silver, and a bare ground check. Rows were 45 ft long on 6 ft centers and were equipped with trickle irrigation. Bare ground rows and all row middles received Command at the labeled rate for weed control. Commercial transplants of the variety ‘Camelot’ were planted June 12, 2000. Transplanting occurred in staggered double rows with rows and plants spaced 18 in. apart on the plastic with 54 plants per plot. Transplants received a drench application of Terrachlor for disease control. Plots were fertigated with Pro-Sol 20-20-20, KNO₃, CaNO₃, and NH₄NO₃ combinations beginning June 15, 2000 and continuing until final pepper harvest for a total of 65 lbs N/A as 92 lbs Pro-Sol/A, 60 lbs CaNO₃/A, 43 lbs KNO₃/A and 94 lbs NH₄NO₃/A. Bare ground plots were hand weeded before first harvest. Fruits were harvested five times beginning August 8 and ending September 28. All data were analyzed by ANOVA methods and means of significant treatment differences were separated using Fisher’s Protected LSD at the 0.05 level of probability.

Pepper fruits (pod number ) at the first harvest were the same for all treatments (Table 1) . At the first harvest, all treatments yielded equally (Table 2). Differences were observed at later harvests with yields from plants on the metalized UV reflective silver mulch being lower. Total yield from the silver mulch treatment was less than half those from the other two mulch treatments (Table 2). Yield of plants growing on bare ground were slightly less than those growing on the silver mulch.

Plants growing on the silver mulch exhibited some degree of chlorosis during the hotter part of the growing season and generally, were not quite as vigorous as those growing on the other mulches. The cause of the chlorosis is unknown, but it is speculated that the intense reflection of the sunlight from the silver surface back into the leaf canopy may have had some destructive effect (light saturation) on the chlorophyll content subsequently reducing the photosynthetic efficiency of the plants growing on the silver mulch. Under intense light conditions experienced during the summer, light saturation which is accompanied with some degree of chlorophyll destruction is a common occurrence in many plant species, particularity species that have the C-3 photosynthetic metabolism. Pepper is one of those species Quantification of chlorophyll is planned in future studies. No significant differences were found in individual pepper fruit pod weight (Table 3). However, the number of fruits produced by plants on the silver mulch was significantly less than the numbers from plants growing on the other two mulch treatments. This also suggests that perhaps the difference in the reflected light intensity from the plastic may have influenced fruit set of the plants growing on it. These results are supported by similar finding from 1999 studies which included only black and white mulches.

Table 1.Pepper fruit numbers (pods/ plot) by harvest at the University of Tennessee Knoxville Experiment Station, 2000.

Means in the same column followed by the same letter are not significantly different according to Fisher’s Protected LSD at P=0.05.

Table 2.Pepper fruit yield (lbs/plot) by harvest at the University of Tennessee Knoxville Experiment Station, 2000.

Means in the same column followed by the same letter are not significantly different according to Fisher’s Protected LSD at P=0.05.

Table 3.Individual pepper fruit (lbs/pod) by harvest at the Univeristy of Tennessee Knoxville Experiment Station, 2000.

Means in the same column followed by the same letter are not significantly different according to Fisher’s Protected LSD at P=0.05.