Multi-Location Evaluation of Copper Fertilization on Cane Yield of Sugarcane (Saccharum officinarum L.) under Alkaline-Calcareous Soils of Southern Punjab, Pakistan

Abstract

Sugarcane (Saccharum officinarum L.) productivity in southern Punjab is constrained not only by macronutrient imbalance but increasingly by latent micronutrient deficiencies on the region's alkaline-calcareous soils, where free CaCO₃ and chronically low organic matter immobilize plant-available copper. A multi-location field trial was therefore conducted during the 2023–24 crop season at three contrasting sites of the Bahawalpur–Bahawalnagar tract ; Haroonabad-1, Haroonabad-2, and Bahawalpur; to evaluate the response of spring-planted CPF-246 cane to graded levels of broadcast copper sulphate pentahydrate (CuSO₄·5H₂O). Five treatments comprising 0, 6, 8, 10, and 12 kg CuSO₄·5H₂O ha⁻¹, applied over a uniform NPK basal of 250–175–125 kg ha⁻¹, were arranged in a two-factor randomized complete block design with three replications at each site. Soil analysis confirmed alkaline pH (8.22–8.40), low organic matter (0.23–0.86%), and contrasting EC (1.31–2.9 dS m⁻¹) and macronutrient status across the three sites. Combined analysis of variance revealed highly significant effects of treatment (F = 14.34, p < 0.01) and location (F = 46.36, p < 0.05) on cane yield, while their interaction was marginally non-significant (F = 2.29, p = 0.0825). Cu fertilization progressively improved cane yield, with pooled mean yields rising from 104,993.8 kg ha⁻¹ in the unfertilized control to 112,843.2 kg ha⁻¹ at the highest tested dose. The greatest cane yield response over the NPK-only control was recorded at 12 kg CuSO₄·5H₂O ha⁻¹ (+7,849.4 kg ha⁻¹; +7.5%), which was therefore identified as the recommended Cu rate for spring-planted sugarcane on the alkaline-calcareous soils of southern Punjab. The inclusion of 12 kg CuSO₄·5H₂O ha⁻¹ as a basal soil-broadcast input, alongside the standard NPK schedule, is recommended to capture the latent Cu limitation on cane productivity in this agro-ecological zone.