Effect of Nano Zinc and Nano Calcium on Growth, Yield, Soil Nutrient Status and Economics of Groundnut (Arachis hypogaea L.) under Rainfed Conditions of the Central Dry Zone of Karnataka, India

Abstract

Groundnut (Arachis hypogaea L.) is one of the most important oilseed crops cultivated under rainfed conditions, where micronutrient deficiencies, particularly zinc and calcium, frequently limit crop productivity. Nano-fertilisers have emerged as efficient nutrient delivery systems because of their greater surface area, enhanced nutrient-use efficiency and controlled nutrient release. A field experiment was conducted during kharif 2023, 2024 and 2025 at the AICRP on Groundnut, Zonal Agricultural and Horticultural Research Station, Hiriyur, Karnataka, to evaluate the effect of nano zinc and nano calcium on the growth, yield, soil nutrient status and economics of groundnut. The experiment was laid out in a Randomised Complete Block Design (RCBD) with seven treatments replicated thrice. The treatments comprised the recommended dose of fertilisers (RDF), foliar application of zinc sulphate, nano zinc at two concentrations, nano calcium at two concentrations and soil application of gypsum at the pegging stage along with RDF. Pooled analysis of the three-year data revealed that soil application of gypsum @ 500 kg ha-1 at the pegging stage along with RDF resulted in superior growth and yield attributes and economic returns, viz. plant height (36.8 cm), nodulation (99 nodules plant-1), root length (28.4 cm), shoot length (41.5 cm) and plant biomass (19.1 g plant-1), a significantly higher number of pods plant-1 (33.9), pod yield (2682 kg ha-1), kernel yield (1883 kg ha-1), haulm yield (4530 kg ha-1), gross returns (₹1,81,031 ha-1), net returns (₹1,15,801 ha-1) and benefit-cost ratio (2.8) compared with RDF alone. Among the foliar nutrient treatments, nano zinc @ 2 g per 15 L of water applied at 25 and 45 DAS produced a significantly higher number of pods plant-1 (32.0), pod yield (2558 kg ha-1), kernel yield (1780 kg ha-1), haulm yield (4456 kg ha-1), gross returns (₹1,72,746 ha-1), net returns (₹1,09,176 ha-1) and benefit-cost ratio (2.7); this treatment was statistically on par with gypsum application for most yield parameters. The treatments had only a marginal influence on post-harvest soil zinc and exchangeable calcium status, indicating efficient nutrient utilisation by the crop. Improved crop performance under nano zinc application was attributed to enhanced chlorophyll synthesis, enzyme activation, auxin metabolism and biological nitrogen fixation, whereas gypsum ensured an adequate calcium supply during pegging and pod development, thereby improving pod filling and kernel development. The study demonstrated that soil application of gypsum at the pegging stage along with RDF is the most effective nutrient management practice for maximising groundnut productivity and profitability under the rainfed conditions of the Central Dry Zone of Karnataka, while foliar application of nano zinc at 2 g per 15 L of water serves as an efficient alternative for improving crop growth and yield.