2017 ASHS Annual Conference

Nursery producers are faced with many water management and labor challenges. Irrigation may occur for several hours a day or for 24 hours per day in order to irrigate the entire nursery and require extensive monitoring and labor, especially when operated manually. Leaching volume is easy to measure manually and leaching fraction (LF) [(volume leached)/(volume applied)*100] is a simple calculation to make that can become the basis for refining irrigation. Our objective was to develop an irrigation/leachate volume sensor and a data logger program that could calculate LF in order to automatically irrigate based on maintaining a predetermined LF. Four leachate sensors and an irrigation sensor were deployed in each zone. The program calculated the LF each day and compared it to the previous day’s LF to determine the amount of irrigation needed to maintain a 15% LF. The adjustment in irrigation run time was scaled so that the farther the LF was from 15%, the greater the increase or decrease in run time. The LF-based system was compared to a commercial nursery’s standard irrigation regime of irrigating 2 hours every other day. Volumetric water content (VWC), LF, plant growth and cumulative water use were investigated on Juniperus conferta ‘Blue Pacific’ in 2015 and 2016 and J. horizontalis‘Blue Rug’ in 2015. Only ‘Blue Rug’ junipers were instrumented. In 2015, the LF-based junipers used 67% less water than the control zone and in 2016, they used 61% less water. In 2015, the average daily VWC was 32 and 33% for the juniper LF-based and control irrigation treatments, respectively. In 2016, the average daily VWC was 28 and 31% for juniper LF-based and control treatments, respectively. From July 7 to October 29, 2015, the growth index increase in the LF-based and standard irrigation for ‘Blue Rug’ was 13.1 and 10.5, respectively, and for ‘Blue Pacific’ was 23.5 and 19.1, respectively (P value=0.9400). From August 3 to October 12, 2016, the average growth index increase for ‘Blue Pacific’ in the LF-based and control irrigation was 8.7 and 8.2, respectively (Pvalue=0.0506). From August 20 to September 25, 2015 the average LF for junipers in the LF-based and control irrigation was 38% and 57% respectively, a 33% reduction in LF. From August 24 to October 11, 2016, the average LF for junipers in the LF-based and control irrigation was 20% and 32%, respectively, a 38% reduction in LF.