Sustainable Yield Intensification in Philippine Cassava Systems

This project generates the scientific information that is required to establish the nutrient uptake and yield relationships for cassava, determines the agronomic use efficiency for individual nutrients to aid in the development of fertilizer recommendations, and establishes 4R-consistent nutrient management practices for smallholder growing systems. The implementation of this project is between 2015 and 2018 in the Philippines.

The project uses an approach that successively reduces the risk for growers to invest in fertilizers, and consists of: 1) an analysis of the existing data to derive nutrient uptake functions for cassava; 2) supporting the existing information with data from on-station trials and trials in commercial fields that demonstrate economic viability and validate nutrient uptake functions; and 3) development of a Nutrient Expert® (NE) Cassava fertilizer decision support tool for the Philippines. Therefore, we will: 1) determine the parameters for internal nutrient efficiency, response to individual nutrients and attainable yields from nutrient omission trials on stations; 2) verify the parameters in trials at farmers’ fields and develop a Beta version of NE Cassava; 3) use the Beta version to generate fertilizer recommendations for a selected number of farmer’s fields; and 4) examine the field results jointly with stakeholders and refine the model as needed.

In 2015-2017, results of one to two years of cassava cropping at four on-station sites (two sites in Laguna, one in Isabela, one in Bukidnon), and three on-farm sites in Agusan del Norte indicated positive response to fertilization, with attainable yields of 20 to 58 t/ha of fresh root yield. In 2017, the beta version of NE for Cassava was developed and subsequently used to generate 4R-based fertilization rates for the individual trial sites. Yield, fertilizer use, and nutrient uptake data from harvested trials have been added to the cassava database. Four on-farm cassava fertilization trials for the optimization of NE Cassava were established in the province of Zambales.
Cassava attainable yields and yield response to nitrogen, phosphorus, and potassium application varied across locations and varieties. Large amounts of nutrients are required by cassava to produce high yields. Fertilizer recommendations based on 4R principles will help farmers improve their yields and profit and prevent severe nutrient mining that could lead to land degradation.