The experiments reported here were conducted in Georgia, US, to record the effects of coloured mulches on root-zone temperatures, plant growth and yield of broccoli. Six-week-old transplants of cv. Packman were planted 30cm apart in rows on 7 October 2004, 25 March 2005 and 9 October 2008. Five plastic mulches and a bare-soil control were compared in the first two experiments, but in the third the bare-soil treatment was replaced by red-coloured plastic mulch.
Drip irrigation was used underneath the mulches. The root-zone temperature, 10cm below soil level, was increased more by dark-coloured mulches (black, blue, red, and grey) than by light-coloured ones (silver and white). The dark-coloured mulches also produced increases in plant growth and yield but only in the spring-sown crop and then not until the mean root-zone temperature exceeded 21 degsC with this cultivar.
However, root-zone temperatures above 25 degsC are detrimental and more likely under dark mulches in summer. The heads of autumn-sown crops suffered chilling injury if frosts occurred before harvesting.
Root Zone Temperature, Plant Growth and Yield of Broccoli (Brassica oleracea (Plenck) var. italica) as Affected by Plastic Film Mulches by Diaz-Perez (2009). Scientia Horticulturae 123 (2): 156-163. The contents of issues of Scientia Horticulturae and abstracts of papers are provided at www.elsevier.com/locate/scihorti.