2018 ASHS Annual Conference

Scientific evidence of soil water potential impact on yield and quality of celery (Apium graveolens L.) production is very limited. A better understanding of the subject could set actionable targets for irrigation scheduling and the use of soil water potential sensors. Celery yield and quality, water use, soil mineral nitrogen (N), plant total N, soil electrical conductivity, root depth and canopy cover were assessed under four irrigation treatments initiated at four different soil water potential targets in Oxnard, CA during Spring 2017. Soil water potential was monitored at 8 and 18 inch depth using Hortau®’s TX4 Field Monitoring Stations. The four treatments consisted of initiating irrigation when soil water potential readings at 8-inch depth reached -20, -30, -40 and -50 kPa, named T-20, T-30, T-40 and T-50, respectively. The amount of water applied at each irrigation was calculated based on the crop evapotranspiration since the last irrigation, with an additional leaching requirement of 30%. Treatments were replicated four times within a randomized complete block design. Each plot consisted of three side-by-side 40 inches-wide and 75 ft long beds, with two celery rows in each bed, and a drip tape on the top and center of the bed. Yield and quality data were collected in the center 20ft of the middle bed of each plot. Total and marketable yield and plant height linearly decreased from T-20 to T-50 (P<0.050). Total and marketable yield were 11.4% and 9.0% smaller, respectively, for T-50 compared to T-20. Whole plant weight and marketable plant weight also decreased from T-20 to to T-50, with significant differences (P<0.05) between T-20 and T-50. There were no trends nor significant differences (P=0.596) of pith among treatments. Water use was very similar, totaling 19.7, 18.9, 18.6 and 18.4 inches for T-20, T-30, T-40 and T-50, respectively. Soil mineral N, plant total N, soil electrical conductivity, rooting depth and canopy cover at harvest were very similar and not significantly different (P>0.05) among treatments. The averages of the highest soil water potential values at 8-inch depth prior to each irrigation were -25.9, -36.2, -43.7 and -52.0 kPa for T-20, T-30, T-40 and T-50, respectively. Overall, the results of this study suggest that initiating irrigation at soil water potential lower than -20 kPa decreases celery yield, plant height and plant weight in proportion with the decrease of soil water potential down to -50 kPa, but it didn’t affect pith.