Microalgae-Based Biostimulants Change Physiological, Agronomic and Fruit Quality Traits of `Solu Red' and `Wakefield' Raspberries

This study illustrates the effect of the microalgae-based biostimulants ‘Algafert’ (0.75% N; 7.40% P2O5, 3.20% K2O, 5.60% free amino acids) and ‘Biofat 600’ (2.70% N, 6.70% Ca, 0.10% P2O5, 0.10% K2O, 6% free amino acids) on the leaf concentration of chlorophyll (SPAD) and nitrogen (mg g-1), cane architecture traits, productivity, biometric and chemical fruit properties of raspberry cultivars ‘Solu Red’ and ‘Wakefield’. This research was carried out in a raspberry plantation established in 10-l pots filled with coco peat in the spring of 2022 (company ‘Floriva’, municipality of Ivanjica). The following treatments were applied: T1 – ʽBiofat 600ʼ (2 foliar applications, 2 l ha-1 per application); T2 – ʽAlgafertʼ (2 foliar applications, 1 l ha-1 per application) + ʽBiofat 600ʼ (1 foliar application, 2 l ha-1) and T0 – control treatment. The first application was performed on May 17, 2024 (40% of opened flowers) followed by the second application during the fruit setting and growth. Both biostimulants’ treatments significantly increased concentrations of chlorophyll and nitrogen after the second application compared to the control. ‘Wakefield’ exhibited significantly higher chlorophyll and nitrogen concentrations compared to ‘Solu Red’. A significantly higher number of fruiting laterals (32.6) and yield per cane (1261.3 g) were recorded in ‘Solu Red’, while the number of fruits per cane did not differ significantly between the tested cultivars. ‘Solu Red’ showed significantly higher values for the fruit volume-related traits and total acids compared to ‘Wakefield’. This study revealed that microalgae-based biostimulants offer a unique opportunity to strengthen the plants’ capacity to cope with challenges amplified by climate change.