Organic onion growth, yield and storage improved by foliar sprays of microalgae and fulvic acid as a natural biofertilizer

Abstract

The use of microalgae as natural biofertilizer in horticulture has recently been reported, while the use of humic substances is widespread. However, the combined use of microalgae with humic substances applied to plant leaves is still unexploited. Thus, the objective of this work was to combine fulvic acid (FA) with the Scenedesmus subspicatus microalga biomass (SC) as a natural biofertilizer applied via leaf in two onion cultivars in organic system. Four experiments were conducted: i) bioassays to verify the bioactive effect of FA, SC and combinations using the Vigna radiata model plant; ii) greenhouse pot experiment with foliar applications of FA, SC and combination in two onion cultivars; iii) field experiment in organic system with foliar applications of FA, SC and combination in two onion cultivars; and iv) onion bulb storage experiment. The bioactive effect of SC, FA and their combinations was identified by promoting changes in root growth of V. radiata. In pots, treatments containing FA, SC and combination promoted increase in fresh and dry leaf mass. The foliar application of FA, SC and combination promoted an increase in field bulb productivity, reduced mass loss in stored bulbs and increased carbohydrate, amino acid and protein contents in onion bulbs.

Microalgae as next generation plant growth additives: Functions, applications, challenges and circular bioeconomy based solutions

“…Foliar application of microalgae extracts has been proven successful in enhancing the growth of several crop plants. Cellular extracts of Chlorella vulgaris , Spirulina platensis , Scenedesmus spp., Nostoc spp., Anabaena spp., Dunaliella salina have been reported to enhance the growth, biomass yield (shoot weight), fruit yield, leaf pigment content, tolerance to abiotic stress such as drought, salinity and temperature stress in horticultural crops such as tomato ( Gitau et al., 2022 ), lettuce ( La Bella et al., 2021 ; Puglisi et al., 2022 ), capsicum ( Elarroussia et al., 2016 ), onion ( Gemin et al., 2022 ) and beans ( Li et al., 2014 ; Elarroussia et al., 2016 ). In addition to the horticulture crops, FS of cellular extracts of Spirulina platensis and Scenedesmus spp., resulted in enhanced root weight, plant growth, number of flowers per plant, earliness of flowering and flower diameter in Petunia x hybrid plant ( Plaza et al., 2018 ).…”

Morphophysiological Parameters and Leek Seed Production Depending on Fulvohumin Treatment and Date of Planting Seedlings

“…Top dressing foliar fertilizer with humates also significantly increased bulb weight and dry matter concentration. Foliar top dressing of onions with fulvic acid increased the fresh and dry weight of leaves, and the content of carbohydrates and protein (Gemin et al 2022).…”