Wood chip mulch thickness effects on soil water, soil temperature, weed growth and landscape plant growth.

Wood chip mulches are used in landscapes to reduce soil water evaporation and competition from weeds. A study was conducted over a three-year period to determine soil water content at various depths under four wood chip mulch treatments and to evaluate the effects of wood chip thickness on growth of 'Husker Red' Penstemon digitalis Nutt. plants. The effects of four wood chip thicknesses (depth of application: 0, 2.5, 5, and 10 cm) on soil water content, weed numbers, soil temperature, and height, width, stalk number, and first flower date of 'Husker Red' Penstemon were investigated. The addition of mulch, at all mulch thicknesses, conserved soil water compared to when no mulch was used. The differences in soil water content likely influenced some of the plant growth factors measured. Weed numbers were significantly higher at the 0 and 2.5 cm mulch thickness compared to the 5 and 10 cm thickness In general, mid-day soil temperatures were highest at the shallower soil depths in the unmulched plots. Flowering plants in 2008 in the unmulched treatment were slightly shorter than in the mulched treatments. There were no significant differences in the number of flower stalks per plant although there was a trend for a lower number of stalks with the mulched treatment. The time of first flower was, on the average, about 2 days earlier for the unmulched treatment compared to the 10 cm mulch thickness. Wood chip mulch helped conserve soil water, which in turn had some effects on plant growth