Container-grown Ornamental Plant Growth and Water Runoff Nutrient Content and Volume Under Four Irrigation Treatments

Abstract

Container-grown woody ornamentals were irrigated according to a percentage of daily water use (DWU) or a traditional irrigation rate to evaluate plant growth, irrigation volume, runoff, and nutrient loss from each irrigation treatment. Deutzia gracilis Sieb. and Zucc. ‘Duncan’, Kerria japonica (L.) DC. ‘Albiflora’, Thuja plicata D. Don. ‘Atrovirens’, and Viburnum dentatum L. ‘Ralph Senior’ were grown in 10.2-L (# 3) containers under four overhead irrigation treatments: 1) a control irrigation rate of 19 mm per application (control); 2) irrigation scheduled to replace 100% DWU per application (100DWU); 3) irrigation alternating every other application with 100% replacement of DWU and 75% DWU (100–75); and 4) irrigation scheduled on a three-application cycle with one application of 100% DWU followed by two applications replacing 75% DWU (100–75–75). Applications were separated by at least 24 h. Total irrigation applied for the 100DWU, 100–75, and 100–75–75 treatments was 33%, 41%, and 44% less, respectively, than the total water applied by the control treatment of 123 L per container. Plants grown under the three DWU treatments had a final growth index greater than or equal to plants irrigated by the control treatment depending on species. Daily average runoff volumes from production areas irrigated with 100% and 75% DWU were 66% and 79% lower than average control runoff of 11.4 L·m−2·d−1 across all collection days. Quantity of NO3–-N lost daily across all collection days for the 100% DWU and 75% DWU irrigation volumes averaged 38% and 59% less, respectively, than the control. Daily losses of PO43–- P quantities across all collection days under the 100% and 75% DWU volumes were 46% and 74% lower, respectively, compared with the control. Irrigating according to the DWU treatments used in this study reduced irrigation and runoff volumes and NO3–-N and PO43–-P losses compared with a control of 19 mm per application while producing the same size or larger plants.