Abstract
Plant biostimulants are of interest as they can stimulate plant growth and increase resource utilization. There is still no information on the use of plant growth-promoters under variable nutritional conditions in the nursery and the effects on tomato seedling growth and plant performance after transplant. This study aimed to evaluate the suitability of gibberellic acid (GA3) or bacterial biostimulant treatments to enhance the growth and quality of greenhouse-grown tomato (Solanum lycopersicum ‘Marmande’) seedlings, fertigated with increasing nutrient rates and to assess the efficacy of these treatments on the early growth of tomato plants. During autumn 2019, tomato seedlings were inoculated with 1.5 g L−1 of TNC BactorrS13 (a commercial biostimulant containing 1.3 × 108 CFU g−1 of Bacillus spp.) or sprayed with 10−5 M GA3 and fertigated with a nutrient solution containing 0, 1, 2 and 4 g L−1 of NPK fertilizer (20-20-20) when they reached the 11th BBCH growth stage for tomato. Subsequently, the seedlings were evaluated in greenhouse cultivation for 60 days until at least the 61st BBCH growth stage (January 2020). The growth of the tomato seedlings increased curvilinearly in relation to the fertigation rates. The GA3-treated seedlings showed similar or even higher growth parameters than the control seedlings fed with 4 g L−1 of fertilizer but with half of the nutrients. The inoculation of the substrate with Bacillus spp. had negative effects in the absence of fertigation but determined a greater growth at the highest fertigation rate. The bacterial inoculum of seedlings had longer-term effects than the GA3 treatment during the plant growth, but these effects were noticeable mainly when the bacterial biostimulant was associated with the highest fertigation rate.
Highlights
Container-grown vegetables are an important agricultural commodity and the seedling nursery production is a sector in constant evolution mainly thanks to the introduction of new technologies, techniques, and cultivars
Seeds of Solanum lycopersicum ‘Marmande’ (Vilmorin, La Ménitré, France) were sown into 24 polystyrene trays (104 cells each) filled with a commercial substrate (SER CA-V7 Special semine, Vigorplant Italia srl, Fombio, Italy, containing 800 g m−3 of a mineral fertilizer NPK 12-11-18) and into 12 similar trays filled with the same substrate inoculated with 1.5 g L−1 of TNC BactorrS13, a commercial bacterial biostimulant with plant growth-promoting bacteria (1.3 × 108 CFU g−1 of Bacillus amyloliquefaciens, B. brevis, B.circulans, B. coagulans, B. firmus, B. halodenitrificans, B. laterosporus, B. licheniformis, B. megaterium, B. mycoides, B. pasteurii, B. subtilis, Paenibacillus polymyxa) and soluble humates, natural plant growth regulators, amino acids, vitamins and trace elements derived from Ascophylum nodosum
We found the highest increase in nitrogen use efficiency (NUE) in GA3 -treated seedlings (+19.1% and +23.2%, respectively, with 2 and 4 g L−1 of fertilizer), whereas the inoculated seedlings had the worst NUE at the lowest fertigation rates (0 and 1 g L−1 ) and did not differ from GA3 -treated seedlings at the highest fertigation rates (2 and 4 g L−1 ), confirming that part of the nitrogen supplied was immobilized by bacteria determining the nutritional stress to tomato seedlings
Summary
Container-grown vegetables are an important agricultural commodity and the seedling nursery production is a sector in constant evolution mainly thanks to the introduction of new technologies, techniques, and cultivars. It is possible to adopt other strategies that aim at improving the water and nutrient use efficiency of the seedlings to reduce the consumption of these resources in the production system, limiting environmental problems and increasing nursery industry sustainability. These goals might be reached by using growth-promoting microorganisms and plant growth regulators [8,9,10,11,12]
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