Creating annual crop type maps for enabling improved food security decision making has remained a challenge in Bhutan. This is in part due to the level of effort required for data collection, technical model development, and reliability of an on-the-ground application. Through focusing on advancing Science, Technology, Engineering, and Mathematics (STEM) in Bhutan, an effort to co-develop a geospatial application known as the Agricultural Classification and Estimation Service (ACES) was created. This paper focuses on the co-development of an Earth observation informed climate smart crop type framework which incorporates both modeling and training sample collection. The ACES web application and subsequent ACES modeling software package enables stakeholders to more readily use Earth observation into their decision making process. Additionally, this paper offers a transparent and replicable approach for addressing and combating remote sensing limitations due to topography and cloud cover, a common problem in Bhutan. Lastly, this approach resulted in a Random Forest “LTE 555” model, from a set of 3,600 possible models, with an overall test Accuracy of 85% and F-1 Score of .88 for 2020. The model was independently validated resulting in an independent accuracy of 83% and F-1 Score of .45 for 2020. The insight into the model perturbation via hyperparameter tuning and input features is key for future practitioners.

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In Bhutan, cultivation of exotic commercial Kiwifruit fruit is new though wild kiwifruit is found aplenty. There is a high scope for kiwifruit cultivation as it is suitable in a wide range of areas in the country. It can also be grown organically due to the lack of any known serious pest or disease. Fittingly, kiwifruit is counted among the most potential high-value fruit crops in the country. Its cultivation is gaining popularity in the current times and it would consequently increase the demand for kiwifruit seedlings. Kiwifruit seeds exhibit physiological seed dormancy which hampers kiwifruit seedling production. Hence, a study was conducted in 2019 and 2020 at ARDC, Wengkhar. In the study, the combined effect of GA3 and growth medium on kiwifruit seed germination was studied using eight treatments with three replications laid out in a Completely Randomized Design. The study aimed to find out the germination parameters like germination percentage, relativized percentage, mean germination time, time taken for 10% germination, and time taken for 25% germination. According to the study, Cocopeat + 1500 ppm GA3 gave the best germination percentage at 51% followed by Biochar + 1500 PPM at 39% while rice bran and compost exhibited a low germination percentage. Overall, the mean germination time was found to be 50 days. The highest relativized percentage of 63 % was observed in Cocopeat + 1500 ppm GA3. As for the time taken to achieve 10% and 20% germination, those treatments with 1500 GA3 application had an advantage of approximately eight days over the others. Overall, considering the average weighted effect of germination percentage and time, Cocopeat + GA3 1500 PPM gave the best result followed by Biochar + GA3 1500 PPM and Cocopeat + GA3 0 PPM. Hence, the study indicates that GA3 treatment in combination with an appropriate germination medium can significantly enhance seed germination in kiwifruit.

Huanglongbing (Citrus Greening) is the most devastating citrus disease caused by phloem-inhabiting bacteria carried by the insect vector, Asian citrus psyllid (Diaphorina citri). In Bhutan, the production and movement of citrus seedlings and new orchard establishment have been restricted after the Citrus Greening disease was detected in most citrus orchards. To address this problem, Agriculture Research and Development Centre-Wengkhar has initiated research on clean citrus propagation through shoot tip grafting. This study assessed the efficiency of shoot tip grafting for the production of clean planting materials. Sweet orange was used as an indicator plant to study disease transmission and symptom expression in some of the potential and released citrus varieties. A total of 15 plants, 3 plants of each cultivar (AREP-1, AREP-2, Aoshima, Wengkhar Tshelu-2 and Yoshida Ponkan) produced through shoot tip grafting were used for bio-indexing. The cultivars were grafted on indicator plants using different grafting techniques (T-budding, side grafting, wedge, and split grafting). A total of twenty-six samples with two samples per cultivar was sent to the National Plant Protection Centre for PCR analysis. The result of PCR showed negative result for Huanglongbing. Thus, shoot tip grafting could be one potential method for clean citrus planting material production.

In Bhutan, naturally occurring local type of pears were grown. Asian or Nashi pears are recent introduction which have become quite popular in eastern Bhutan since it was promoted by Agriculture Research and Development Centre (ARDC) Wengkhar. Although, horticulture has been gaining momentum in recent years, many growers in Bhutan follow traditional methods of crop cultivation and thus, majority of farmers still do not adopt important aspects of fruit production like fruit thinning. In commercial fruit farms elsewhere, fruit thinning is an essential management practice. However, in Bhutan, it is rarely practiced and there is no empirical study on its benefits. Fruit thinning is believed to be beneficial in increasing yield efficiency whilst also sustaining or increasing market returns by improving the fruit size and quality. Thus, a study was conducted in 2019 and 2020 at ARDC, Wengkhar. Effect of hand thinning on Hosui pear was assessed by randomly sampling 15-year-old Hosui trees with four replications – each tree treated as an experimental unit. Canopy of these trees were divided into two equal halves so that one half represents thinning and the other half non-thinning treatments. The treatments were randomly assigned to the two halves of each tree. Hand thinning resulted in significant increase in the fruit weight by 39%, fruit diameter by 12% and fruit height by 12 % over the non-thinning treatments; Total Soluble Solids (TSS) content, an indicator of taste, was greater by 9%. However, the overall yield was lower in the thinning treatments but in the second year of the study, the mean fruit yield in thinning treatments increased by 55% while the yield of non-thinning treatments plummeted by 33%. Hence, the study indicates that fruit thinning has significant effect on fruit quality and yield stability.