Optimizing Neolamarckia cadamba geometry and disease management for ginger production in semi-arid Bundelkhand

Abstract

Agroforestry systems that combine high-value spice crops with multipurpose tree species provide opportunity to improve productivity, soil health, and carbon sequestration. However, research regarding the ideal spacing of Neolamarckia cadamba and effective disease management measures for ginger in agroforestry systems is limited. A one-year field experiment was conducted during 2024–25 at RLBCAU, Jhansi to evaluate the effects of Neolamarckia cadamba planting geometry and disease management on ginger growth, productivity, soil properties, tree biomass-carbon dynamics and economic returns. A factorial randomized block design was implemented, consisting of four tree spacing (S₀: Sole cropping, S₁: N. cadamba at 5 × 3 m, S₂: N. cadamba at 5 × 4 m and S₃: N. cadamba at 5 × 5 m) and four disease management treatments (T₀: Control, T₁: 4% metalaxyl + 64% mancozeb @ 2 g kg⁻¹, T₂: Hot water treatment followed by application of T. harzianum @ 10 g kg⁻¹ with soil application of neem cake, and T₃: T. harzianum @ 10 g kg⁻¹ with enriched farmyard manure (FYM) prepared in a 1:5 ratio). The results indicated that S₁ exhibited the greatest plant height (66.08 cm), number of leaves (97.96 plant⁻¹), the primary rhizomes (6.86 plant⁻¹), rhizome weight (1.43 kg plant⁻¹), rhizome fresh yield (9.66 Mg ha⁻¹), and total fresh biomass (10.76 Mg ha⁻¹). Treatment, T₁ yielded the highest rhizome weight (1.56 kg plant⁻¹), rhizome fresh yield (10.48 Mg ha⁻¹), and total fresh biomass (11.54 Mg ha⁻¹) across disease management approaches. Agroforestry substantially enhanced soil fertility, with S₁ exhibiting the highest chemical properties. The Neolamarckia cadamba + ginger system with a spacing of 5 × 3 m achieved the highest above-ground biomass (68.57 Mg ha⁻¹), carbon stock (40.61 Mg ha⁻¹), and CO₂ sequestration potential (149.02 Mg ha⁻¹). Economic analysis indicated maximum net returns (US$ 5,771.07 ha⁻¹), and B:C ratio (2.36) under S₁. The findings indicate that Neolamarckia cadamba based agroforestry, at a spacing of 5 × 3 m combined with efficient disease management, improves ginger productivity, soil fertility, and the potential for climate change mitigation.