Replicated irrigation trials were performed on cauliflower (Brassica oleracea var. botrytis cv. Symphony) in California’s Salinas Valley during 2018 and 2019. The CropManage online decision-support system was used to guide evapotranspiration-based irrigation scheduling. Overhead sprinklers were used to establish the crop with 60-70 mm of water, followed by surface drip for the remaining crop cycle. A randomized complete block design, with six replications, was used to administer four treatments near 50%, 75%, 100% and 150% of estimated full crop water requirement (T50, T75, T100, T150) during the drip phase. An additional drip treatment at 125% (T125) was added in 2019. Applied water totals across treatments ranged from 199-410 mm in 2018 and 179-369 mm in 2019 (plus 35 mm of precipitation). No significant differences were observed between total curd (head) yields from T100 and T150 in year 1 (> 30 Mg ha-1), although marketable yield from T150 was greater. Total yield of T100 and T125 were significantly greater than T150 during year 2, but marketable yield was similar among T100-T150. No significant difference was observed in fresh or aboveground dry biomass production from T100 and T150. Significant reductions in yields and biomass production were observed in T50 and T75 for both years. T100 and T150 had the highest irrigation water productivity with respect to marketable yield. Nitrogen uptake and fertilizer N recovery were highest in T100 and T150 during 2018, but no significant treatment differences were observed in 2019. These field trials demonstrated that estimating crop evapotranspiration and irrigation requirements of cauliflower through a decision support service such as CropManage can be a reliable tool for irrigation scheduling.
