Assessment of Walnut Grafting Success under Locally Fabricated Hot Callusing Technology with IoT based Environmental Control

Tshering Penjor, Pema Yangdon, Lungki, Thinley Gyeltshen, Mandira Acharya, Tshering Pem, Tshewang Dorji, Domang, Sangay Dendup

Walnut grafting under open conditions often achieves a relatively low success rate of 0-20%, primarily due to difficulties in maintaining optimal environmental conditions. Grafting is typically carried out in February and March when the plants are dormant, during which the temperatures fall below 15°C. However, successful walnut grafting requires an optimal temperature of 27°C and a relative humidity of 90%, conditions that are difficult to maintain in an open environment. Hot callusing technology presents a solution to achieve and sustain these optimal conditions. This study, conducted at the Agriculture Research and Development Centre (ARDC) Wengkhar and Drepong village, Mongar Dzongkhag, aimed to develop an effective and sustainable hot callusing technology. The system was developed using locally available materials integrated with IoT (internet of things) technology to automate and monitor environmental conditions. The efficacy of locally fabricated hot callusing systems on the success rate of walnut grafting was evaluated both on-station and on-farm. The study initiated on-station in 2023 with 180 seedlings achieved a graft success rate of 78%. The second study conducted on-farm in 2024 with 1,170 grafted seedlings, achieved a 76% success rate. For both the sites, the grafting was done in February month when the plants were still at dormancy stage. Unlike the past studies, this study made use of vertical space and IoT for automation and monitoring. Further, investment analysis demonstrated a positive Net Present Value (NPV) and a high Internal Rate of Return (IRR), confirming the economic viability of this technology for walnut nursery enterprise development. The findings indicate that the locally fabricated hot callusing system, coupled with IoT technology, provides a sustainable and profitable solution for walnut grafting in Bhutan, with the potential for broader applications in agricultural enterprise development.

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