Biostimulant Application, under Reduced Nutrient Supply, Enhances Quality and Sustainability of Ornamental Containerized Transplants

Abstract

Ornamental containerized transplant production needs high doses of controlled release fertilizers (CFR), but it is known that there is an environmental risk caused by inadequate fertilization management. To the best of our knowledge, amino acid-(AaB) and seaweed extract-(SeB) based biostimulant application, in ornamental transplant production, is still poorly studied. Therefore, the aim of this work was to assess the hypothesis that, under reduced nutrient supply, SeB and AaB applications, via foliar spray, can promote quality and sustainability in the production of high-quality ornamental seedlings with a 90-day growing cycle. The CRF incorporated into the peat-growing medium was Osmocote Exact Mini in formulation N:P:K = 15 + 9 + 11 (3 months). Six treatments were compared in two economically important potted (0.3 L in volume) ornamentals: Abelia × grandiflora and Lantana camara: T1 = conventional full CRF dose: 4 gL−1 per pot; T2 = limited CRF dose: 50% of T1; T3 = T2 + MC-Extra® [SeB 0.5 gL−1]; T4 = T2 + MC-Extra® [SeB 1.0 gL−1]; T5 = T2 + Megafol® [AaB 1.5 mL L−1]; T6 = T2 + Megafol® [AaB 2.5 mL L−1]. The research results showed that the application of 50% CRF plus biostimulant application resulted in plant performance greater than or equal to those raised under the conventional CRF full dose. In particular, S1 (Abelia × grandiflora ‘Edward Goucher’) and S2 (Lantana camara ‘Little Lucky’) behaved differently concerning the Megafol® dose under 50% CRF; compared to T1, in A. × grandiflora young transplants, T5 increased root morphological characteristics, as well as number of leaves, leaf area, and dry biomass accumulation; in L. camara, T6 achieved higher performance. The application of biostimulants under 50% CRF also improved, in both A. × grandiflora and L. camara, the physiological and agronomical Nitrogen Use Efficiency, compared to a full CRF dose. This study can support decision-making in terms of agronomic technique choices in line with the sustainable development of high-quality ornamental transplant production.