Response of Yield of Chinese Potato to Thermochemical Organic Fertilizer Fortified with Different Zinc Sources

The current study was undertaken to assess the impact of thermochemically processed organic fertilizer (TOF) enriched with various zinc (Zn) sources on the soil fertility status, nutrient availability, and tuber yield performance of Chinese potato (Plectranthus rotundifolius L., var. Suphala) under microplot conditions in the Onattukara region during the summer season of 2023. The experimental layout followed a Randomized Block Design (RBD) comprising nine treatments replicated thrice. The treatments included TOF fortified with four distinct Zn sources—zinc sulfate (ZnSO₄), zinc oxide (ZnO), zinc carbonate (ZnCO₃), and zinc ethylenediaminetetraacetate (ZnEDTA)—applied at two concentration levels (500 and 1000 mg Zn kg⁻¹ TOF), along with an unfertilized control to serve as a baseline. The incorporation of Zn-fortified TOF significantly enhanced multiple agronomic and soil parameters. Notably, TOF fortified with ZnEDTA at 500 mg kg⁻¹ exhibited superior performance in terms of total tuber yield (714.39 g/plot), marketable yield (452.72 g/plot), and number of tubers per plant (23.81), thereby establishing its efficacy in improving productivity under the low fertility, acidic sandy soils typical of the Onattukara agro-ecosystem. Furthermore, marked improvements were recorded in soil nutrient availability and tuber nutrient content, particularly for zinc and other associated micronutrients. These results highlight the pivotal role of chelated zinc formulations like ZnEDTA in enhancing nutrient-use efficiency and crop performance when applied through bioresource-based carriers. The findings underscore the potential of integrating thermochemical recycling with micronutrient fortification as a sustainable strategy in circular agricultural systems for improving soil health and crop yield, particularly in resource-constrained and zinc-deficient tropical soils.