RSA2 - Agronomy

Optimized feertility solutions

Leader: Imran Malik
Collaborators: Laothao Youbee, Sophearith Sok, Thuy Cu Thi Le

RSA-2 targets chemical, physical, biological or technological problems limiting cassava yield, while implementing land- use practices that are highly productive, sustainable, economically viable, and environmentally safe in LAC and ASEAN regions.

The Alliance Cassava Program has developed an agronomic package for sustainable production systems that includes:

timely planting, appropriate fertilizer application practice (organic and inorganic), and weed control. These practices are adopted by farmers to varying extents. There is a large gap in terms of the farmers implementing the technology in an efficient and sustainable manner. Furthermore, research on fertilizer management needs to focus on site-specific nutrient management. For best-practice farming, soil testing is an important tool, as test results provide the basic facts on fertilizer use and improves the prediction accuracy of a profitable response to nutrient applications.

The RSA-2 team targets problems limiting cassava yield by experimenting and promoting land-use practices that are highly productive, sustainable, economically viable, and environmentally safe, with a focus on Latin America and the Caribbean (LAC) and Southeast Asia (SEA).

In 2020, our research focused on fertilizer requirements and site-specific nutrient management in SEA. Trials on soil management and agronomic practices were conducted to develop improved cassava production technology for germplasm evaluation. These trials were carried out with smallholder farmers, government and industry representatives of four countries in SEA, namely Laos, Cambodia, Vietnam and Indonesia. The aim is to expand the use of new technologies among growers with varying levels of support from private companies.

Alternative inputs within local farming and processing systems

Results from a trial on potassium balance were shared with farmers via on-farm demonstrations in Laos and Cambodia.

Opportunities for high-impact genetic solutions to agronomic challenges

In Vietnam, 21 new CIAT clones (elite lines) were compared with the popular varieties KM419 and KM94. Wide variation was observed among the elite lines in terms of fresh root yield. The highest yielding line, GM579-13, also had the highest starch content (30.1%), compared to KM419 and KM94 which had 26.9% and 28.7% starch content, respectively.

Fresh root yield

(A) and starch content (B) of 21 elite lines, compared with two popular varieties (between red dotted lines) after 8 months of growth. Planting density was 1.0 m X 0.8 m (i.e., 12,500 plants per hectare), and 90 kg N/ha, 60 kg P2O5/ha and 90 kg K2O/ha was applied as fertilizer. Values are means of three replicates with standard error bars. *w=white roots and B=brown roots.

Agronomic practices that support the transition to more diversified farming systems

Different soil management options were tested, including intercropping with different legumes, grass strips and using cassava residues from the previous year. Intercropping with legumes was the preferred option for soil management (improving soil nutrient status) and has been scaled up. However, stakeholders have expressed concern about scarcity of farm labor.

A 20-month long experiment conducted in Vietnam to study the potential for year-round cassava production demonstrated that fresh root yield increases with the duration of the crop, although during the rainy season starch content goes down.

LaTre and KM94 yields

(A) and starch content (B) of cassava variety La Tre and KM94 at different harvest dates (crop duration in months). The crop was planted at the same time in April of the previous year (2018). Means are followed by standard errors (n = 3).