This document summarizes results from nutrient omission trials conducted across cassava production zones in Tanzania to determine nutrient limitations and parameterize the QUEFTS model. Over 100 nutrient omission trials were planted across three zones, with varying numbers of active sites due to drought. Soil sampling, plant measurements, leaf sampling, and intermediate harvests were completed for most sites. Preliminary results showed variable responses to fertilizer treatments between districts within zones, with nutrient limiting effects not being very distinct at 4 months after planting. Final harvest results and data from other zones will provide a broader understanding of nutrient limitations and cassava response to fertilizers to guide the QUEFTS model.

1. Fertilizer recommendation use case field
trials:
Results from Tanzania
Annual Review and Planning Meeting
Ibadan, Nigeria, 5th – 7th December 2016
Tanzanian team

2. Objectives
• Assess nutrient limitations across pilot cassava production zones in Tanzania
• Collect data to parameterise QUEFTS model

3. Number of Nutrient Omission Trials per zone
Zone NOT planted Active NOT sites Comments
Lake zone 85 44 Drought
South 4 4
East 28 11 Drought
Total 117 59
Zone NOT planted Active NOT sites Comments
Lake zone 120 120 1 MAP old
South 0 0 To be
planted in
Dec 2016
East 80 80 3 WAP old
Total 200 200
Season One
Season Two

4. Data collection status
Type Status at Lake zone Status in the South Status in the East
Soil sampling Done (during site
selection)
Done (during site
selection)
Done (during site
selection)
Non-
destructive
plant
measurements
Done (1, 2.5 , 4 and
7.5 MAP)
Done (1, 2.5 and 4 MAP) Done (1, 2.5 and
4 MAP)
Leaf sampling Done (4 MAP) Done (4 MAP) Done (4 MAP)
Intermediate
harvest
Done (4 MAP) Done (4 MAP) Done (4 MAP)
Final harvest Not Done Not Done Not Done
Weather data In progress In progress In progress

5. Overview of preliminary results
Non Destructive
Monitoring for Laze
zone
(Districts of Bunda, Mara and Sengerema)

6. Main stem length
Different responses of main stem length to
treatments appear between districts:
• No fertilizer effect at Bunda
• Fertilizer response in Mara but no clear
distinction of most limiting nutrient
• Nitrogen seems to be most limiting at
Sengerema

7. Main stem diameter
No clear response nor distinction of most
limiting nutrient

8. Overview of activities
Destructive Harvest
In Lake Zone

9. BUNDA: Fresh storage roots weight
High variability, no clear differences between treatments

10. BUNDA: Tops weight

11. SENGEREMA: Fresh storage roots weight

12. SENGEREMA: Tops weight

13. Preliminary concluding remarks
• Difference in responses appeared between districts, but nutrient limiting
effects were not very distinct at 4MAP (rain stopped just after 2nd fertilizer
application (60% N and K, at 2.5MAP)
• 7.5MAP measurements and the final harvest may be more indicative
• Results from different states are expected to provide a general picture of most
limiting nutrients, indigenous nutrient supply by soils and cassava response to
fertilizers in the pilot districts
• This will guide the parameterisation of QUEFTS model for the assessment of
site specific nutrient requirements of cassava in Tanzania