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Open field experiments were conducted to investigate the effects of plant growth promoting rhizobacteria (PGPR) biofertilizer on processing tomato, grown under three different irrigation regimes. The field effectiveness of rhizobacteria inoculation on total biomass, yield, water use efficiency (WUE), carotenoid, and ascorbic acid production was examined in 2015 and 2016. The experimental design used was randomized block and the number of replications was four for each treatment. There were three different irrigation regimes: rain-fed control (RF), deficit water supply (WS50), and optimum water supply (WS100), which was delivered by drip irrigation in accordance with daily evapotranspiration (ETc). The test was performed on the Uno Rosso F1 processing tomato hybrid. Red fruit were measured at harvest in August and high-performance liquid chromatography (HPLC) was used for analysis. We evaluated yield quantity and total carotenoids and their composition (lycopene and β-carotene) depending on water supplement in 2 years. The marketable yield varied between 14.7 t·ha−1 and 126.9 t·ha−1 depending on treatment. The average soluble solids content (SSC) of the treatments ranged from 3.0 to 8.4. The total carotenoid yields of the treatments ranged from 0.8 to 40.4 kg·ha−1 and the average lycopene yield of the treatments ranged from 0.6 to 34.1 kg·ha−1. The effect of PGPR treatment was clearly positive for harvested yield, but this effect only prevailed under irrigated conditions.

Carotenoids and tocopherols are important phytonutrients of orange-colored carrots. The main goal of this work was to investigate the effects of irrigation on the content and composition of carotenoids and tocopherols in an orange-colored carrot cultivar (Bangor) compared with a rain-fed control. The experiment was conducted for 2 years with a considerably different amount of precipitation during the growing season (576 mm in 2010 and 190 mm in 2011). Six carotenoids and four tocopherols were detected and quantitatively determined. Significant negative correlations were found between water supply and content of total carotenoids and total tocopherols. Irrigation significantly decreased the concentrations of these phytonutrients during the arid year of 2011. Water supply did not affect the carotenoid and the tocopherol composition, which can be an important factor for functional food manufacturers. A significant positive correlation was found between total carotenoid and total tocopherol concentrations, which is very favorable from a nutritional point of view.

A 3-year experiment was conducted in central Hungary comparing the effect of an irrigation treatment on content and yield of dry matter, storage carbohydrates, vitamin C, total flavonols, and total polyphenols of onion (Allium cepa L.) grown from sets. Rain-fed plots were set as controls. Conditions during the first 40 days of the growing season had a decisive effect on yield and bulb size; warmer and dryer weather during this period resulted in lower yield. Colder and wetter weather conditions resulted in higher bulb yield, but also decreased accumulation of secondary metabolites. Dry matter content values ranged between 12% and 14% and were not influenced by the water supply. Storage carbohydrate-to-dry matter ratio was not changed by the water supply. Total flavonol contents (sum of the concentrations of nine individual flavonols) varied between 430 and 753 mg·kg−1 on a fresh weight basis. Total polyphenol values ranged between 607 and 1029 mg·kg−1 on a fresh weight basis. A statistically significant correlation was found between flavonol content and polyphenol content for the rain-fed treatment, but this was not the case for the irrigation treatment. Irrigation significantly increased total flavonol and total polyphenol concentrations during the dry years. Irrigation significantly increased the bulb yield by 33% to 160%, depending on the year. Consequently, by applying irrigation, yields of nutritive compounds became 1.5 to two times higher.

Two experiments were carried out in 2010 to determine how cultivation period/harvest season, plant water status/irrigated, or rainfed and foliar sulfur supplementation influences the yield, sulforaphane, phenolics content, and polyphenol composition of broccoli cultivar Parthenon. Yield was significantly higher in the fall harvests. Foliar sulfur treatment induced earliness in irrigated broccoli in the fall harvest season of main florets by 44%. Sulforaphane content was higher in the fall harvests regardless of treatments. Harvest season also influenced total polyphenol content with the highest values measured in the spring season. Sulfur treatment in combination with irrigation increased total polyphenol content by 24% in spring and this change was statistically significant. Harvest season also affected trolox equivalent antioxidant capacity (TEAC) values with the highest values (4.3 mmol·kg−1) also measured in spring. In the irrigated treatment alone or irrigated treatment combined with sulfur treatment, spring season values were higher by 24% and 11%, respectively, compared with fall values and the difference between treatments was significant. Caffeic acid glucoside was one of the major phenolic components in both spring and fall season harvests, whereas ferulic acid glucoside could only be detected in spring florets. From the measured phenolic components, gallic acid content was the only one that was significantly raised by foliar sulfur supplementation in both spring and fall harvests in irrigated or rainfed treatments. Maximum gallic acid values (7.1 to 7.2 mg·kg−1) occurred in the irrigated combined with foliar sulfur treatment of the fall harvest in side and main florets, respectively. The season, irrigation, and foliar sulfur supplementation were related changes in other phenolic component contents and are also described in detail.