Irrigation management in container nursery production to reduce water use, runoff, and offsite movement of agricultural chemicals

Irrigation applications based on daily water use (DWU) were compared to a traditional irrigation rate to investigate the effects on plant growth, irrigation and runoff volumes, and nutrient quantities carried in runoff for container-grown woody ornamentals. Plant DWU was determined by measuring the change in substrate volumetric moisture content between irrigations. Irrigation treatments were: (1) a control of 19 mm-ha applied per application; (2) 100% DWU per application; (3) alternating every other application with 100% and 75% DWU; and (4) a three application cycle replacing 100% DWU followed by two applications of 75% DWU. Total irrigation applied by the 3 DWU treatments was reduced 25% to 75% compared to the control depending on treatment and species. Runoff from irrigation applied at 100% and 75% DWU volumes were 66% and 79% less than the control across all measurement days. For all taxa final growth index of DWU treatments was greater than or equal to the control. Relationships of potential evapotranspiration and growth to actual evapotranspiration of Spiraea fritschiana Schneid. 'Wilma' show promise for developing a model for irrigation scheduling. The DWU treatments used in this study reduced irrigation volumes, runoff, and NO3- -N and PO43- -P losses compared to a control of 19 mm·d-1 while producing the same size or larger plants.