Layered double hydroxides intercalated with borate anions: a new source of boron for plants
Boron (B) is generally present in soil as boric acid (H3BO3), a non-ionized molecule with weak retention in the soil and very leachable. The B leaching may occur especially when soluble sources are applied in sandy soils in high-rainfall environments and high rates of B may cause toxicity in plants....
| Autor: | |
|---|---|
| Tipo de recurso: | tesis doctoral |
| Estado: | Versión publicada |
| Fecha de publicación: | 2020 |
| País: | Brasil |
| Institución: | Universidade Federal de Viçosa (UFV) |
| Repositorio: | LOCUS Repositório Institucional da UFV |
| Idioma: | inglés |
| OAI Identifier: | oai:locus.ufv.br:123456789/33825 |
| Acceso en línea: | https://locus.ufv.br/handle/123456789/33825 |
| Access Level: | acceso abierto |
| Palabra clave: | Fertilizantes de micronutrientes Fertilidade do solo Nanotecnologia Polímeros CIENCIAS AGRARIAS::AGRONOMIA::CIENCIA DO SOLO |
| Sumario: | Boron (B) is generally present in soil as boric acid (H3BO3), a non-ionized molecule with weak retention in the soil and very leachable. The B leaching may occur especially when soluble sources are applied in sandy soils in high-rainfall environments and high rates of B may cause toxicity in plants. The use of a slow release source of B, such as layered double hydroxides (LDHs) intercalated with borate can potentially minimize the B leaching 1n soils, and reduce the plant toxicity. This thesis consists of four chapters with the following objectives: (1) synthesize and characterize the magnesium-aluminum LDH intercalated with borate (Mg>Al-B-LDH) and evaluate the potential of this source as a matrix for storage and sustaimed release of B for plants 1n a clayey soil; (ir) evaluate the B availabihty and leaching from Mg>A1-B-LDH and H3BOs in a sandy soil, and the B bioavailability of these two sources mn consecutive cultivations of sunflower; (iii) synthesize, characterize, and evaluate the agronomic performance of a new fertilizer produced from alginate microspheres containing Mg>Al-B-LDH (LDH-B-ALG); and (iv) investigate the leaching and bioavailabihty of B1n a sandy soil, in which H3BOs, Ulexite, alginate beads containing H3BO3 (BA-ALG), and LDH-B-ALG sources were used. The fertilizers synthesized were characterized by X-ray diffraction (XRD), attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), and scanning electronic microscopy (SEM). A soil incubation study and single greenhouse experiment with sunflower plants were performed mn a clayey soil using H3BOs and Mg>AI-B-LDH sources. Mg>2AI-B-LDH and H3BO: at two rates of B (10 and 20 mg dm”) were also incubated (1, 2, 3, 5, 10, 20, and 40 days) in a sandy soil with 81% of sand, and the B availability was evaluated. For the leaching study, 20 mg dm” of B from Mg>AI-B-LDH and HsBO3 was Incorporated into to a sandy soil, and incubated between 1 and 30 days before leaching. Sunflower plants were cultivated 1n two consecutive seasons (greenhouse experiment) using Mg>AI-B-LDH and H3BOs sources, and six rates of B (0, 0.5, 1,2,3, and 5 mg dm”). The new slow release fertilizer LDH-B-ALG was synthesized, characterized, and evaluated through the B release and leaching test in soil with 71% of sand. A greenhouse experiment with two responsive species (sunflower and cotton) was carried out using a factorial 2 x (4 + 1) with two soil pH (6.5 and 7.5), four sources of B (LDH-B-ALG, BA-ALG, H5BO3, and Ulexite), and a treatment control, without the application of B. Additionally, the leaching study was replicated 1n a sandy soil with 92% of sand, in which 20 mg/dm” of B from LDH-B-ALG, BA-ALG, HBO», and Ulexite were Incorporated 1n the soil and incubated between 1 and 40 days before leaching. A greenhouse experiment with leaching was established with the rate of total B of 2 mg dm” 3 four sources of B (LDH-B-ALG, BA-ALG, H:BOs, and Ulexite), and one treatment without application of B. In the greenhouse experiment with single cultivation of sunflower in the clayey soil, Mg>2AI-B-LDH and HsBOs sources were solubilized similarly and released B equally to the plants. Thus, the profile of B release from Mg2Al- B-LDH (powder form) used in agricultural soils with normal acid pH value can be compared to the commercially soluble source (H3BO3). In the leaching test carried out in a sandy soil (81% of sand), the slow release of B from Mg>Al-B-LDH resulted im a significant reduction in B leached compared to H3BOs. After two consecutive cultivations of sunflower in a sandy soil, the boron rate of 5 mg dm” applied as H3BO» resulted in plant toxicity, while Mg>AI-B-LDH promoted a slow release of B to the plants. The chemical characterization by XRD, ATR-FTIR, and SEM analyses for LDH-B-ALG showed that Mg>A1-B-LDH (powder) was successfully incorporated into to alginate polymer. The B release and leaching were much lower from LDH-B-ALG compared to conventional B sources. The new fertilizer LDH-B-ALG showed be a suitable source in high-rainfall areas, especially for sandy soils, supplying B im a more adjusted way and reducing leaching losses. In the B leaching test in soil with 92% of sand, throughout the incubation period, the percentage of B leached from LDH-B-ALG was significantly lower compared to all B sources. The lower leaching from LDH-B-ALG application im a greenhouse experiment with leaching, resulted in a higher shoot and total B uptake from total cultivation of sunflower and cotton. The LDH-B-ALG application under controlled conditions was the most promising B source to be used 1n soils prone to B leaching. This study lays a robust platform for future field studies on the validation of these slow-release materials 1n agricultural settings. Additionally, the alginate beads contamning LDHSs and fertilizers will serve as foundation for future studies focusmg on macro and micronutrients, that 1t 1s Important to sustaimnabihty of agriculture and food security. Keywords: Slow-release. Micronutrient. Fertilizer. Polymer. Nanotechnology. |
|---|