Do foliar applications of nickel increase urease activity and nutrient levels in pecan leaflets?

Abstract

Nickel (Ni) deficiency limits the production of pecan. Concentrations of mineral nutrients and urease activity in leaflets of young pecan plants cv. Pawnee were evaluated in response to foliar applications of Ni as Ni sulfate or Ni citrate, or as chelates with EDDHA, EDTA, or DTPA. Significant variations were found in N-total concentration with Ni-EDDHA (27.17 ± 0.98 g/kg) and Ni-sulphate (28 ± 0.89 g/kg), where the latter together with Ni-citrate were high in phosphorus concentrations. Levels of Ni<sup>2+</sup> (3.70 mg/kg), Mn<sup>2+</sup> (222.73 mg/kg) and Zn<sup>2+</sup> (38.69 mg/kg) were all increased in leaflets sprayed with Ni-EDDHA but the Mn<sup>2+</sup> concentrations were similar for leaflets sprayed with Ni-sulphate. The Ni-DTPA spray significantly reduced foliar Fe<sup>2+</sup> concentration (73.66 ± 3.44 mg/kg). No significant effects of the sprays were observed on the concentrations of total chlorophyll or carotenoids. The plants sprayed with Ni-EDDHA showed significant increases in leaflet area and leaflet dry weight and also in root dry weight. The urease showed maximum activity in leaflets sprayed with Ni-EDDHA, Ni-citrate and Ni-sulphate. This study suggests growers of the pecan should consider foliar sprays of Ni-EDDHA or Ni-sulphate to increase the levels of Ni in their trees if Ni is a growth-limiting factor.

Accumulation Capacity of Nickel and Zinc in Yerba Mate Cultivated in Soils with Contrasting Parent Materials

“…The positive effects of Ni on yerba mate leaf and branch production has been observed in other crops such as pecan and soybean (Barman et al, 2020;Barrera et al, 2022). Nickel participates in the structural composition of the urease enzyme (Dixon et al, 1975), which contributes to better N use and consequent production of more shoot dry matter, and plays a physiological role in herbivory defense (Davis et al, 2001) and stress tolerance modulation (Fabiano et al, 2015).…”

“…General recommendations for Ni fertilization are still in formative stages since there are few studies investigating this requirement. Some studies have reported positive responses to Ni application in crops such as soybean, bean, pecan, and coffee (Fernandes et al, 2011;Lopes, 2014;Barman et al, 2020;Barrera et al, 2022).…”