Use of Routine Leaching Fraction Testing to Guide Irrigation at a Container Nursery

Abstract

Efficient irrigation during container plant production is difficult to achieve as irrigation is scheduled daily or multiple times per day to maintain an adequate supply of water in the limited substrate volume. Leaching fraction (container drainage/water applied) testing is one strategy to monitor and adjust irrigation to limit excessive container drainage. We compared an automated irrigation schedule based on routine leaching fraction testing and weather (LFI) with a nursery's traditional irrigation practice (TIP). Compared to TIP, LFI reduced water applied in four of five sprinkler-irrigated trials without a notable growth affect; LFI increased water applied in a fifth trial but plant growth was also increased. Compared to TIP, LFI reduced water applied in all three micro-irrigated trials but also reduced growth in one of the trials. LFI reduced water applied by an average of 21% [57.8 vs. 73.1 kL·ha−1· d−1 (15,300 gal/acre/day) or $3,000 ha−1yr−1 ($1,200/acre/year) at a pumping cost of $0.53/kL ($0.20/1000 gal). We concluded that the greater economic benefit of water savings was to provide increased capacity for additional production under consumptive water use limitations rather than to reduce the unit cost of production. Index words: automation, evapotranspiration, sprinkler, micro-irrigation, weather. Species used in this study: Leyland cypress, Cupressus × leylandii A.B. Jacks. and Dallim., Parson juniper, Juniperus squamata Gordon ‘Expansa Parsonii', crape myrtle, Lagerstroemia indica L. × fauriei Koehne ‘Natchez', Indian hawthorn, Raphiolepis indica (L.) Lindl., sweet viburnum, Viburnum odoratissimum Ker Gawl.