Water is considered the most limiting factor in newly transplanted container plants (Costello and Paul, 1975; Scheiber et al., 2007), and the most common cause of death among recently transplanted container-grown plants is water stress (Costello and Paul, 1975; Nelms and Spomer, 1983). This could be attributed to water loss from the original root ball as a result of absorption by roots, evaporation from the soil surface, and movement of water from the root ball into the backfilled soil (Costello and Paul, 1975; Nelms and Spomer, 1983). Moisture in the root ball can be very different from the surrounding soil, and in fact, the root ball may experience drought conditions even when soil is well-watered (Costello and Paul, 1975; Nelms and Spomer, 1983). Water in the surrounding soil does not tend to move into the root ball; thus, until established, water applied to the root ball is critical. In previous research, irrigation outside the original root ball did not aid in rapid establishment of transplanted trees (Gilman et al., 1998). Instead, increasing irrigation frequency was more effective than applying larger volumes of water infrequently to transplanted trees. There appears to be a maximum volume of irrigation water needed for plant functions and, if applied correctly, above which there is no added benefit to the plant (Gilman et al., 1998). This implies that once that volume of water is applied, adding more can be wasteful.
Scheduling landscape irrigation based primarily on daytime air temperature and the number of days of precipitation is not well correlated with plant water needs (Qualls et al., 2001). Instead, monitoring soil moisture is a technological approach that can more accurately quantify plant water use by measuring the rate of drying of the backfill soil and transplanted root ball. Installing soil moisture sensors in both the soil backfill and the transplanted root ball could be used to efficiently schedule and control irrigation, thereby reducing water use and lowering direct costs associated with irrigation (Dukes et al., 2005; Qualls et al., 2001). The objective of this research was to determine the effect of scheduling irrigation application based on volumetric water content in either the backfill soil or root ball on establishment and growth of two native shrub taxa.
Dukes, M.D., Cardenas-Lailhacar, B. & Miller, G.L. 2005 Residential irrigation based on soil moisture Resource, Eng. & Technol. for a Sustainable World 12 4 6
Gilman, E.F., Black, R.J. & Dehgan, B. 1998 Irrigation volume and frequency and tree size affect establishment rate J. Arboricult. 24 1 9
Price, J.G., Wright, A.N., Tilt, K.M. & Boyd, R.L. 2009 Organic matter application improves posttransplant root growth of three native woody shrubs HortScience 44 377 383
Qualls, R.J., Scott, J.M. & DeOreo, W.B. 2001 Soil moisture sensors for urban landscape irrigation: Effectiveness and reliability Amer. Water Resources Assn. 37 547 559
Scheiber, S.M., Gilman, E.F., Paz, M. & Moore, K.A. 2007 Irrigation affects landscape establishment of burford holly, pittisporum, and sweet viburnum HortScience 42 344 348
Wright, A.N., Wright, R.D., Browder, J.F. & Jackson, B.E. 2007 Effects of backfill composition on post-transplant root growth of Kalmia latifolia J. Environ. Hort. 25 145 149