Efficiency of foliar application of sparingly soluble sources of boron and zinc in citrus

Abstract

This study evaluated leaf supply of zinc (Zn) and boron (B) using either soluble or sparingly soluble fertilizers in young sweet orange trees. Three experiments were set up in a greenhouse to compare two sources and four doses (control, low, adequate and high) of fertilizers as follows: (i) Experiment I (B): boric acid and calcium borate; (ii) Experiment II (Zn): Zn sulfate and Zn oxide; and (iii) Experiment III (B + Zn): boric acid + Zn Sulfate and Zn Borate. The sparingly soluble sources were effective in increasing the Zn and B leaf concentration. Dry matter of the aerial part increased 18 % with B applications in adequate concentration independent of the B fertilizer sources. In contrast, trees did not grow well with applications of adequate concentration of Zn as Zn Sulfate or high Zn concentration as Zn borate. Superoxide dismutase activity in leaves increased with applications of low concentration of Zn as Zn oxide and decreased with high concentration of Zn from either source. Polyphenol oxidase activity increased with application of adequate concentration of B as boric acid and high concentration of B as calcium borate. Furthermore, the upper concentrations of Zn were toxic in orange trees when the source was Zn sulfate. Increases in plant growth without damage to leaf tissue and positive responses of key enzymes of orange trees in a range of nutrient concentration applications demonstrated the practical use of sparingly soluble fertilizers to supplying B and Zn foliarily to plants.

Characterization and use efficiency of sparingly soluble fertilizer of boron and zinc for foliar application in coffee plants

“…This decrease seems not to have been regulated by leaf concentration since the soluble source provided a smaller concentration of Zn in the leaves when compared to Zn oxide and Zn borate. Thus, the cause of toxicity to plants with a high dose of Zn sulfate may have been due to the high saline concentration of the spray solution prepared with a soluble source, which in contact with the leaves causes tissue damage and can reduce the LA , Macedo et al 2021. This damage can Characterization of B and Zn sources for coffee be verified in coffee leaves of the experiments II (Zn) and III (B and Zn), characterized by yellowish sores that evolved in the leaf limb (Figs.…”

“…However, these fertilizer sources still offer challenges regarding application technology, such as the limited amount to be applied in the leaves to avoid phytotoxicity due to high saline indices (Kah et al 2018), the interaction that may occur with other products in the spray tank mix , and the necessity to perform new applications with each new shoot, since these micronutrients have low mobility in the phloem (Lacerda et al 2018;Leite et al 2007). In this scenario, the development of concentrated suspensions, based on micronutrients in Sparingly soluble fertilizers (SSF), such as oxides and carbonates, is the most significant technological advance that has resulted in a wide range of products optimized for growers (Bell and Dell 2008;Macedo et al 2017;Macedo et al 2021). To improve the efficiency of micronutrients in SSF, they have been used as micro or nanoparticles, since sources of low solubility with smaller particle sizes may favor the absorption of nutrients by plants due to greater contact surfaces (Du et al 2015).…”

“…During the use of SSF, the particles are adhered to the leaf surface and can serve as a solid phase to prolong the supply of micronutrients to the plant (Wang and Nguyen 2018). In contrast, the foliar application of soluble sources generally results in high uptake of the micronutrient by the leaves at first, but soon there is decrease in the rate of absorption (Rossi et al 2019;Macedo et al 2021).…”

Foliar Application of ZnSO4 and CuSO4 Affects the Growth, Productivity, and Fruit Quality of Washington Navel Orange Trees (Citrus sinensis L.) Osbeck

“…Zn participates in the activity of several enzymes (RNA, DNA polymerases, and dehydrogenases), as well as the maintenance of membrane structure and cell division [39][40][41]. Moreover, [42] demonstrated that providing B and Zn through foliar application to orange plants increased nutrient concentrations in leaves and promoted plant growth. Micronutrients are essential macronutrients for plant growth, yield, and quality.…”

Application of Optimal Combined Microfertilizers of Boron, Molybdenum, and Copper Improves Root Tuber Yield Trait and Photosynthetic Response Characteristics in Pseudostellaria heterophylla

“…Boron, Mo, and Cu are essential elements for plant growth and development (Wu et al, 2017a). These elements play important roles in regulating plant growth and development, especially in photosynthesis and other metabolic processes, and in organic matter transportation and distribution, and have been verified in many plants (Macedo et al, 2021). For example, one study showed that spraying B fertilizer on the leaves of Raphanus sativus effectively increased the chlorophyll content, enhanced photosynthesis, and promoted sugar metabolism during the flowering process (Wang et al, 2018).…”