Effect of biofertilizers on yield and morphological parameters of onion cultivars

The present study evaluated the effect of different organic fertilizers on the morphological parameters and yield in two different onion cultivars. Proper use of organic fertilizers in appropriate amounts could be helpful to growers from the economic point of view. Field experiments were conducted to study the effect of three different organic biofertilizers on yield and morphological parameters of two onion cultivars ‘Stuttgarter Riesen’ and ‘Rote Laaer’ during 2016 and 2017. The investigated treatments included: B-Stimul^® – a mixture of bacterial and algal extracts, EkoBooster 2^® – organic matter and NPK, and VermiFit A® – an extract of compost produced by Californian earthworms, peat, nutrients, plant hormones, enzymes, amino acids, and sugars. The following parameters of onion plants were evaluated: number of leaves, bulb diameter, bulb weight, marketable and total yields. The study showed that all the results were affected by the growing season (higher values were recorded in 2016). In ‘Stuttgarter Riesen’, EkoBooster 2^® application resulted in the highest bulb weight in 2016 (67.16 g) and in 2017 (55.17 g) and in the highest number of leaves in 2016 (6.66) and in 2017 (6.30), which led to the highest marketable bulb yield in 2016 (3.47 kg m⁻²) and in 2017 (2.53 kg m⁻²). In ‘Rote Laaer’ in 2016, EkoBooster 2^® application resulted in the highest number of leaves (7.06), bulb diameter (54.32 mm) and bulb weight (79.30 g). In 2017, the largest bulb diameter (54.13 mm) and the highest bulb weight (71.79 g) and marketable bulb yield (2.39 kg m⁻²) were determined after VermiFit A^® application. EkoBooster 2^® showed the best effect on parameters such as the number of leaves, bulb weight, and marketable bulb yield of the cultivar ‘Stuttgarter Riesen’ and positively affected the parameters of ‘Rote Laaer’ during 2016, while in 2017 VermiFit A^® showed better results as compared to the other treatments.