Effect of Potassium Levels on Soil and Leaf Nutrient Status of Nagpur Mandarin (Citrus reticulata)

Abstract

Potassium regulates enzymatic activities and stomatal movement, improving water-use efficiency and sugar transport within plants. Along with phosphorus, it supports rapid root growth and promotes protein synthesis. It also improves plant health and resistance to diseases, pests, and nematodes. Potassium deficiency reduces photosynthesis and yield, while excess nitrogen with low potassium can lead to poor fruiting and physiological disorders. The study highlights the significance of balanced and split potassium application along with foliar nutrition in enhancing macro- and micronutrient uptake, which is crucial for sustainable citrus production systems. A field experiment was conducted during 2022–23 at farmers’ fields in Pardi and Sawandri villages of Nagpur district on 10–12-year-old fruit-bearing orchards. The experiment included different potassium treatments and was laid out in a Randomized Block Design. Among all treatments, T₉ (RDF + 300 g K at BT (December) + 300 g K after 60 days + KNO₃ @ 1.5% spray after 90 days) was found significantly superior over other treatments. This treatment recorded higher leaf nutrient concentrations, including total nitrogen (2.19 and 2.29%), total phosphorus (0.099 and 0.123%), total potassium (1.40 and 1.46%), and total sulphur (0.24 and 0.23%) at Pardi and Sawandri villages, respectively. Similarly, total micronutrient content in leaves was also higher under this treatment, with iron (79.46 and 79.47 mg kg⁻¹), zinc (18.50 and 19.34 mg kg⁻¹), manganese (61.51 and 62.79 mg kg⁻¹), and copper (14.00 and 14.17 mg kg⁻¹) at Pardi and Sawandri, respectively. In addition, improved soil nutrient availability was observed with the same potassium treatment. The values recorded were nitrogen (322.50 and 331.30 kg ha⁻¹), potassium (498.19 and 435.32 kg ha⁻¹), iron (7.29 and 7.33 mg kg⁻¹), and zinc (0.86 and 0.84 mg kg⁻¹) at Pardi and Sawandri villages, respectively. Overall, the results indicated that the combined application of RDF with split doses of potassium and foliar spray of KNO₃ significantly enhanced both leaf nutrient status and soil nutrient availability in Nagpur mandarin orchards.