Effects of different colored film mulches on the growth and bolting time of radish (Raphanus sativus L.)

Abstract

Radish (Raphanus sativus L.) is cultivated for the production of leafy and root vegetables and is one of the most economically important vegetables in Asia. Plastic film mulches are often used to improve vegetable yield. However, their effects on radish root zone temperature (RZT) and yield have not been well evaluated. The objective of this study was to determine the effects of RZT, as affected by different colored plastic mulches, on the growth and bolting of radish. Treatments were composed of three plastic film mulches (transparent, black, and green) with bare soil as a control. Two cultivation trials were conducted in spring and fall. For spring planting, the soil heat accumulation and the mean diurnal trend of RZT were the highest in the transparent group, followed by black, green, and bare soil. Moreover, film mulching significantly increased the root length, root diameter, and root weight compared to those in bare soil. The mean, maximal, and minimal RZTs at three different stages (seedling, shooting, and mature stages) were also measured and significant differences were found at seedling and shooting stages, but not at the mature stage. Thus, when the foliage of radish covered the top of the row at the mature stage, soil heat accumulation was possibly less affected by direct solar radiation. In the beginning of spring, the temperature often decreased to < 10 °C, which induces premature bolting, a serious problem for radish cultivation. The higher RZT detected under film mulches was significantly effective in suppressing bolting. Our results revealed that transparent film mulches have the best effects on radish yield and bolting, followed by black and green mulches. Further, the high soil heat accumulation mediated by film mulches is beneficial for vegetative growth and yield and delaying bolting in radish.