Increased plant quality and water savings in Pelargonium × hortorum in response to reduced irrigation frequency

Abstract

Limiting irrigation frequency may present an alternative approach to conventional irrigation practices, leading to water savings whilst maintaining crop yield and/or quality. This may be particularly relevant in commercial nurseries with appropriate irrigation technology. Pelargonium × hortorum Bullseye Cherry plants were grown under glasshouse conditions under either well-watered (WW; daily replacement of 100% of evapotranspiration (ET)), frequent (FDI), or infrequent (IDI) deficit irrigation regimes (50% of ET supplied daily or cumulatively every 4 days, respectively) for 24 days. Stomatal conductance (gs) and leaf water potential (Ψleaf) were measured as indicators of plant water relations. Plant quality was determined by canopy volume. Water use efficiency (WUE) was established as the ratio of shoot dry biomass to total water applied. Both FDI and IDI decreased g. FDI resulted in a more positive Ψleaf, whilst IDI decreased Ψleaf over the experimental period. Deficit irrigation frequency had no effect on either plant volume or biomass during the initial 12 days of the experiment, although by Day 24, both IDI and FDI were significantly lower than WW plants (albeit FDI plants had a greater biomass than IDI plants). This corresponded with IDI and FDI showing a higher WUE than WW plants during the first half of the experiment, but this effect was diminished as growth decreased under both deficit irrigation treatments. During deficit irrigation, irrigation frequency had two main effects on P. hortorum. FDI prevents the onset of leaf water deficit and partially maintains biomass accumulation. However, IDI reduces growth compared to FDI and produces more compact plants, thereby increasing ornamental quality, whilst also enhancing WUE during the early stages of the experiment. This suggests that irrigation frequency can be altered to deliver specific grower objectives.