Evaluation of the Efficacy of Two New Biotechnological-Based Freeze-Dried Fertilizers for Sustainable Fe Deficiency Correction of Soybean Plants Grown in Calcareous Soils

Abstract

Currently, fertilization with synthetic chelates is the most effective agricultural practice to prevent iron (Fe) deficiencies in crops, especially in calcareous soils. Because these compounds are not biodegradable, they are persistent in the environment, and so, there is the risk of metal leaching from the soils. Thus, new, more environment-friendly efficient solutions are needed to solve iron-deficiency-induced chlorosis (IDIC) in crops grown in calcareous soils. Therefore, the central aim of this work was to prepare new freeze-dried Fe products, using a biotechnological-based process, from two siderophores bacterial (Azotobacter vinelandii and Bacillus subtilis) cultures (which previously evidenced high Fe complexation ability at pH 9) and test their capacity for amending IDIC of soybean grown in calcareous soils. Results have shown that A. vinelandii iron fertilizer was more stable and interacted less with calcareous soils and its components than B. subtilis one. This behavior was noticeable in pot experiments where chlorotic soybean plants were treated with both fertilizer products. Plants treated with A. vinelandii fertilizer responded more significantly than those treated with B. subtilis one, when evaluated by their growth (20% more dry mass than negative control) and chlorophyll development (30% higher chlorophyll index than negative control) and in most parameters similar to the positive control, ethylenediamine-di(o-hydroxyphenylacetic acid). On average, Fe content was also higher in A. vinelandii-treated plants than on B. subtilis-treated ones. Results suggest that this new siderophore-based formulation product, prepared from A. vinelandii culture, can be regarded as a possible viable alternative for replacing the current nongreen Fe-chelating fertilizers and may envisage a sustainable and environment-friendly mending IDIC of soybean plants grown in calcareous soils.

Nano-Sized Antioxidative Trimetallic Complex Based on Maillard Reaction Improves the Mineral Nutrients of Apple (Malus domestica Borkh.)

“…Zn sprays enhance the fruit Zn content and result in the higher activities of carbohydrate metabolism-related enzymes, contributing to the accumulation of carbohydrates ( 46 ). Fe sprays increase the concentrations in leaves and decrease the fruit firmness and total phenolic compounds ( 40 , 47 ), while they are considered a highly effective method for preventing and amending iron chlorosis ( 48 ). Although the impact of exogenous mineral treatments on fruits has been studied and utilized extensively, there is still a lack of research focusing on mineral nutrition.…”

Foliar application of 3‐hydroxy‐4‐pyridinone Fe‐chelate [Fe(mpp) 3 ] induces responses at the root level amending iron deficiency chlorosis in soybean

“…Chlorophyll levels were lowest at the V3 leaf stage (between 35 and 40 days after planting depending on the Fe treatment, Figure 2), which is coherent with what was described in other studies with field‐grown soybean plants under Fe deficiency (Bai et al, 2018; Nenova, 2006). As shown after supplementation of other Fe‐chelates compounds (Bin et al, 2016; Ferreira et al, 2019; Martín‐Fernández, Solti, et al, 2017; Qiu et al, 2017), the pigment accumulation in leaves increased progressively, putatively reflecting the recovery of the photosynthetic apparatus, which was impaired due to Fe deficiency.…”

“…For example, soil application of Fe‐nanoparticles showed a positive effect in shoot biomass, but not at the root level (Cieschi & Lucena, 2018). Azotochelin chelating agent (Ferreira et al, 2019) or the biodegradable chelating agent [S,S]‐EDDS (López‐Rayo et al, 2019) did not impact biomass accumulation despite increasing SPAD values.…”

“…The chemical characteristics of the soil are described in Table 1. During the assay, the pH was continuously monitored and plants were watered every 2 days with a nutrient solution composed of: 1.2 mM KNO 3 ; 0.8 mM Ca(NO 3 ) 2 ; 0.3 mM MgSO 4 ·7H 2 O; 0.2 mM NH 4 H 2 PO 4 ; 25 μM CaCl 2 ; 25 μM H 3 BO 3 ; 0.5 μM MnSO 4 ; 2 μM ZnSO 4 ·H 2 O; 0.5 μM CuSO 4 ·H 2 O; 0.5 μM MoO 3 ; 0.1 μM NiSO 4 ; 0.1 g L −1 CaO; 0.06 g NaHCO 3 (Ferreira et al, 2019; López‐Rayo et al, 2016).…”

Identification of Beneficial Microbial Consortia and Bioactive Compounds with Potential as Plant Biostimulants for a Sustainable Agriculture

“…Strains belonging to this species have been proven to exert PGP on several crops to do their ability to form biofilm and colonize plant-tissues [ 90 , 91 ]. Among the two strains belonging to the Azotobacter , A. vinelandii DSM 2289 was reported to increase the growth, chlorophyll content and iron content of soybean plants grown in calcareous soil [ 40 ], whereas A. chroococcum LS132 is a nitrogen fixing bacterium with the ability to improve the growth of tomato plants (unpublished results, AGRIGES). B. amyloliquefaciens LMG 9814 is a PGP strain known to produce alpha-amylase, alpha-glucosidase, iso-amylase production, and B. licheniformis PS 141 is an indole acetic acid (IAA) producing bacterium isolated from rhizosphere (unpublished results, AGRIGES).…”