Trichoderma harzianum Reveals Significant Performance over Copper Sulphate by Visible Microbial Re-establishment in the Recovery of Phytophthora infestans-Infected Potato under Zero-tillage Paddy-straw Mulch in East Kolkata Wetland Area

Abstract

Zero-tillage paddy-straw-mulched potato farming is a low-input surface-planting method whose success depends on the biological condition of the tuber-straw-soil interface. In the sewage-treated paddy fields of the East Kolkata Wetland area, monsoon-driven auto-nutrient recharge makes beneficial microbial growth more important than fertiliser dependence. This study evaluated whether Trichoderma harzianum could support recovery of Phytophthora infestans-infected potato tubers under approximately 11 inches of paddy-straw mulch and whether visible Trichoderma-type growth on jute-bag sheet surfaces could indicate beneficial microbial re-establishment. Sixteen 75 sq ft beds were established with store-bought Kufri Jyoti tubers. Treatments compared clean and infected tubers, CuSO4-based surface sterilisation, T. harzianum-based biological sterilisation, four and six watering events, weed removal or grass-mat conditions, and foliar or surface application of the control agent. The infected-tuber + CuSO4 + grass-mat system produced a mean yield of 3,300.50 kg ha-1, whereas infected tubers treated with T. harzianum produced 14,637.00 kg ha-1. Under infected conditions, T. harzianum gave better recovery and yield than CuSO4 under both watering schedules. The best overall model was healthy tuber selection, field preparation through rice-potato practice or weed removal, surface sterilisation with T. harzianum and soil pretreatment with T. viride, producing 24,754.00 kg ha-1. One-way ANOVA confirmed a strong treatment-system effect on yield, F(5,10) = 75.25, p = 1.32 x 10^-7, and Kruskal-Wallis testing was also significant, H = 14.47, p = 0.013. Visible growth appeared earlier in biological treatments (40 days) than in CuSO4-treated beds (50-60 days), supporting its value as a practical indicator of microbial re-establishment.