Effect of Super Nano Urea and Sulphur on Soil Properties and Yield of Cowpea

Abstract

The present study investigated the impact of super nano urea (SNU) and sulphur on soil properties, nutrient availability and yield of cowpea (Vigna unguiculata L.) grown in nutrient-deficient Alfisol. A field experiment was laid out in RCBD design with 13 treatments and 3 replications, conducted during kharif 2024 at the AICRP on Arid Legumes, UAS, GKVK, Bengaluru, using different combinations of soil-applied nitrogen and sulphur along with foliar application of super nano urea. Results revealed that available nitrogen showed significant improvement, with the highest value recorded under 100% RDF + 20 kg S ha⁻¹, while phosphorus and potassium remained unaffected. Available sulphur increased significantly with basal and foliar S application and micronutrients (Fe, Mn, Zn and Cu) showed slight numerical improvement under balanced N–S nutrition. Soil biological activity responded favourably, where 100% RDF + 20 kg S ha⁻¹ recorded the highest dehydrogenase and urease activities, while SNU-based treatment 75% RDN + 15 kg S ha⁻¹ + SNU @ 8 ml l⁻¹ remained statistically on par, indicating soil enzymatic activity under reduced nitrogen input. Yield data showed that 100% RDF + 20 kg S ha⁻¹ produced the highest seed 1754.82 kg ha⁻¹ and haulm 2559.12 kg ha⁻¹ yields, closely followed by 100% RDF and 75% RDN + 15 kg S ha⁻¹ + SNU @ 8 ml l⁻¹, demonstrating that foliar super nano urea at higher concentration can effectively supplement reduced basal nitrogen. The findings highlight the potential of integrating SNU with sulphur to improve nitrogen management efficiency, enhancing soil enzymatic activity and achieving higher productivity of cowpea under the conditions of the study.