Short-cycle, plant production requires frequent irrigation and readily available nutrients to support plant growth. However, excess irrigation can lead to higher leach volumes and nutrient losses that can slow plant growth while increasing offsite nutrient movement into sensitive areas. The objective of this study was to evaluate the effect reducing leaching has on P losses during coleus (Plectranthus scutellarioides) production over a four-week production cycle. Coleus plugs were grown in 3-quart containers filled with a 3 pinebark:1 peat:1 vermiculite substrate amended with 0.3 kg m–3 N and P2O5 kg m-3. Irrigation was applied at 298 mL (1.05 cm) during a single two-minute cycle per day as a standard treatment versus coleus grown under a sensor-controlled irrigation system that ceased application once leaching occurred. Leachate was captured in one plant per replication for weekly measurement of pH, EC, and DRP. No differences in coleus growth index or shoot and root biomasses at 4 weeks after planting (WAP) occurred between coleus following either irrigation regimen. However, coleus subject to the sensor-controlled irrigation resulted in reductions in cumulative irrigation and leachate volumes of 40% and 69%, respectively, that led to a 45% reduction in cumulative DRP leached compared to coleus following the standard timed irrigation regimen. Limiting irrigation to reduce the incidence and volume of leaching can significantly decrease DRP losses without sacrificing coleus growth.
