Nepheline Syenite and Phonolite as Alternative Potassium Sources for Maize

Some silicate rocks are a rich source of potassium (K), with the possibility for use in agriculture. The present study aimed to evaluate the agronomic efficiency index (AEI) of nepheline syenite (NS) and phonolite (PN) rocks in comparison with potassium chloride (KCl) as a K source in maize production. An experiment was conducted in a greenhouse in Ilha Solteira, São Paulo, Brazil. A maize hybrid was grown in 8 L pots filled with 6 kg of soil with a low K concentration and contrasting physical attributes (medium and sandy texture). A completely randomized design in a 3 × 6 factorial scheme was used, consisting of three K sources (NS, PN, and KCl) and six rates (0, 50, 100, 150, 200, and 400 mg kg−1) with four replications. All plants were harvested 45 days after emergence to evaluate biomass production, macronutrient (N, P, K, Ca, Mg, and S) concentration and uptake, stem diameter, and leaf chlorophyll index. After crop harvest, soil was collected for further chemical evaluation, which included organic matter (OM), pH, cation exchange capacity (CEC), H+Al, Al, sum of bases (SB), base saturation (BS), P, K, Ca, Mg, and S. In addition, AEI of NS and PN were also verified in relation to KCl. The application of NS and PN had a similar effect on soil chemical attributes (MO, pH, SB, CEC, and BS) as well as on the concentrations of K, Ca, Mg, and S, in both soils. The increase in NS and PN rates provided linear growth of shoot dry matter. Leaf macronutrient concentrations were similar for NS and PN compared to KCl. All three K sources (NS, PN, and KCl) increased K accumulation in maize plants. Maize treated with KCl had the largest AEI, followed by PN and NS. However, the results indicated similar AEI with both rocks as a K source for maize, especially with application of the highest K rates. This research demonstrated the efficiency of NS and PN as alternative K sources for maize.

Bokashi, simple superphosphate, and fertigation for the growth and nutrition of hybrid Cattleya (Orchidaceae)

Potted flower production is an important floricultural activity. However, there have been few studies on the fertilization management of orchids. Fertigation with urea and potassium chloride is feasible, but little information is available regarding the interaction of these fertilizers with other sources of nutrients. Thus, the present study evaluated the effects of application of bokashi and a simple superphosphate and their interactions with fertigation on the growth and nutrition of hybrid Cattleya. Seedlings of Laeliocattleya Drumbeat × Laeliocattleya Gold Digger hybrid were submitted to two ferti-irrigation levels (absent and present) using urea and potassium chloride as nitrogen and potassium sources, respectively. As complementary fertilization, bokashi and superphosphate were applied singly and in combination. A commercial fertilizer (Peters®) was used as an additional control. Fertigation increased plant height; leaf area; number, length, and diameter of pseudobulbs; dry mass of leaves, pseudobulbs, and roots; and content of chlorophyll, carotenoid, and nitrogen. The application of bokashi resulted in dry mass gain in all plant organs. The combination of fertigation and bokashi was superior to the commercial fertilizer in terms of increased leaf area, chlorophyll A content, carotenoid content, and dry mass.

New Insights of Potassium Sources Impacts as Foliar Application on ‘Canino’ Apricot Fruit Yield, Fruit Anatomy, Quality and Storability

This is the first report to study the impacts of potassium sources on apricot fruit yield, quality and storability as a preharvest foliar application. Five sources of potassium (K-humate, K-sulphate, K-nitrate, K-silicate and K-citrate), plus water as a control treatment, were applied individually at 0.2% three times on ‘Canino’ apricot over the 2019 and 2020 seasons. The results showed that all potassium salts, applied foliarly, have potential to improve yield, fruit color, and some fruit physical attributes, such as: weight, size and firmness, as well as a reduced lipid peroxidation, accompanied by a low fruit malondialdehyde content reflected in a high tolerance during storage. The K-nitrate treatment was more effective in the improvement of fruit yield, preharvest quality parameters and keeping fruit postharvest quality characteristics from sharp decline during cold storage. Concerning fruit anatomy, K-nitrate and K-citrate showed thicker cuticle and epidermal parenchyma cell diameters, while the K-silicate induced the highest cell wall thickness. K-nitrate was the most economical, and could be recommended for apricot growers in the Nubaria region of Egypt.