SOUTHEAST ASIA By Lovely Luar, Mirasol Pampolino, Apolonio Ocampo, Arnold Valdez, Dale Francis Cordora, and Thomas Oberthür C assava is the third most import- ant source of calories next to rice and maize in tropical countries. However, many years of inadequate at- tention has tagged cassava as the “poor man’s crop.” Ironically, cassava’s on-going contribution to food security and its many industrial uses amounts to a large and positive impact on rural industrial devel- opment and on-farm income. Cassava’s rising demand for food, feed, and indus- trial purposes is driving a need to increase its production. In Southeast Asia, more than 8 million farmers grow cassava (CGIAR, 2015). Cassava production in the region accounts for 22% of world production (FAOSTAT, 2017). Traditionally, farmers produced cassava for food. However, over the past 50 years, particularly in Cambodia and Indonesia, cassava grown for industrial purposes has steadily increased. Thailand is now the world’s second largest cassava producer next to Nigeria and is the world’s top cassava exporter (Treesilvattanakul, 2015). Increased cassava production is serving a rising demand for cassava-based livestock feed, starch, and bio-fuels. A large yield gap between average and potential yields of cassava in Southeast Asia indicates an opportunity to increase cassava production through intensification. The average yield of cassava in Southeast Asia ranges from 4 to 27 t/ha (Figure 1, Continuous cassava cultivation without fertilizer application will lead to soil nutrient depletion and cause yield losses over time. Fertilizer recommendations based on the principles of 4R Nutrient Stewardship will help cassava farmers reap the benefits of their investment in fertilizer. ABBREVIATIONS AND NOTES: N = nitrogen; P = phosphorus; K = potassium. KEYWORDS: yield gaps; tuber yield; food crop production; sustainable intensification. https://doi.org/10.24047/BC102211 IPNI Project PHL-5 M. Pampolino/IPNI Image Cassava Response to Fertilizer Application Better Crops/Vol. 102 (2018, No. 2) 11