Plastic Mulches Affect Crop Microenvironment, Plant Growth and Fruit Yield in Bell Pepper (Capsicum annum L.)

There are numerous studies on the use of plastic mulches for peppers, although relatively few have focused on the microenvironmental and physiological impacts of plastic mulches on bell pepper.  The objectives were to determine the effects of plastic film mulches on root zone temperature (RZT), plant growth, and fruit yield in bell pepper.  The study was conducted in Tifton, Ga. in the fall of 2002 and the spring of 2003 using eight colored plastic mulches.  Plastic mulch color influenced the microenvironmental, physiological, and yield responses of bell pepper plants.  Plastic film mulches differed in their soil-warming ability, with RZTs in both spring and fall being highest in black mulches and lowest in silver mulches. The percentage of photosynthetically active radiation (PAR) reflected from the mulches was highest in silver mulches and lowest in black mulches.  The mean RZT under the plastic mulch decreased with increasing percentages of reflected PAR.  Silver mulches had among the highest values of soil water status, although neither soil water content nor soil water potential had relationship with RZT.  In the fall season plant growth attributes during the first 28 days after transplanting were among the highest in silver mulches and the lowest in black mulches.  Both marketable and total yields were higher on silver mulches and lowest on black mulch in the fall, while they were in general higher on silver with a black strip mulch and lowest on white and silver1 mulches in the spring.  The reduced plant growth and fruit yields in black mulches during the fall were probably due to the increased RZTs, and thus higher heat accumulation, that resulted in higher plant heat stress conditions compared to silver and white mulches.  Fruit yield decreased with mean seasonal RZTs above 27 ºC.  The optimal RZT for bell peper fruit yield was calculated to be 26.1 ºC.