Effect of zinc source and application rate on groundnut (Arachis hypogaea L.) productivity in calcareous soil

Groundnut ( Arachis hypogaea L .) is a vital oilseed crop widely grown in tropical and subtropical regions, particularly valued for its oil and protein content. However, Zinc (Zn) deficiency limits groundnut productivity in calcareous soils due to high pH and CaCO 3 -induced Zn fixation, often causing 15–20% yield loss. A factorial randomized block design field experiment was carried out to compare two Zn sources (ZnSO 4 , Zn-EDTA) at four rates (0, 5, 10, 15 mg Zn kg − 1 soil) to identify the most effective source and and suitable application rate for groundnut in calcareous soil (pH 8.11, CaCO 3 6.54%, DTPA-Zn 0.57 mg kg − 1 ). Zn-EDTA significantly outperformed ZnSO 4 across all growth, yield, and nutrient-uptake parameters. Pod, kernel, and haulm yields rose progressively with Zn rate, peaking nominally at 15 mg Zn kg − 1 (2269, 1472, and 3011 kg ha − 1 ) but statistically at par with 10 mg Zn kg − 1 (2227, 1444, and 2987 kg ha − 1 ), against control values of 1837, 1148, and 2507 kg ha − 1 , respectively. Nitrogen, phosphorus, and potassium uptake followed the same pattern. Post-harvest soil N, P, and K declined with increasing Zn rate, reflecting greater crop uptake, while residual soil Zn was highest and most persistent under Zn-EDTA. The 10 mg Zn kg⁻¹ dose produced results similar to those obtained with 15 mg Zn kg⁻¹, indicating that application from 10 mg Zn kg⁻¹ onward provided similar productivity and nutrient uptake under the tested calcareous soil conditions.