ESTIMATING YIELDS AND YIELD GAPS: Experiences from East Africa - - PowerPoint PPT Presentation

International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org

ESTIMATING YIELDS AND YIELD GAPS: Experiences from East Africa

Godfrey Taulya, Lydia Wairegi, Piet van Asten

International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org

PRESENTATION OUTLINE

• 1. General approach
• 2. Yield estimation in banana/plantain systems
• 3. On-farm monitoring study vs. one-time farm visit survey
• 4. Non-destructive bunch weight estimation
• 5. Yield-determining factors and yield gaps

International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org

GENERAL APPROACH

• 1. What is happening in

farmer fields ?

• 2. Study single factors in

controlled environments

• 3. Field validation and testing

for interactions

• 4. Modeling to understand

interactions and extrapolate

• 5. Proposing technologies for
• n-farm testing

International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org

Understanding existing spatial variability at regional scale

0 125 250 km

• L. Kivu
• L. Edward
• L. Tanganyika
• L. Victoria

Rwanda Uganda Tanzania Burundi DRCongo Kenya

30°E 35°E 0° 5°S

International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org

Understanding existing spatial variability diagnostics at farm scale

Michael Okumu, Severine Delstanche

International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org

YIELDS IN BANANA/PLANTAIN SYSTEMS

• Integrative index for

impacts of:

• constraints
• cultural practices
• Yield  bunch weight
• Harvests are year-round
• Temporal variations in

fresh bunch weight

International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org

YIELD DATA COLLECTION BY FARMERS

• One-time farm visits during surveys patchy data
• Mature bunches may be weighed
• Immature bunches: visual ‘guestimates’ + extrapolation
• Farm monitoring studies comprehensive data
• Challenge: Synchronizing farm visit with harvest operations
• Yield data collection by farmers in monitoring studies
• Extra demands on the farmer (time and labour)
• Literacy/numeracy skills; accuracy and consistency in data
• Restricting studies to literate farmers can bias datasets
• Greater resource endowment, higher standard of management

are correlated with higher literacy levels

International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org

ESTIMATION OF FRESH BUNCH WEIGHT

• General allometric function for estimation of fresh bunch weight (FBW, kg)

at harvest was established through linear regression: Where:

• H is number of hands per bunch
• F is number of fingers on second-last hand
• V is the pseudostem volume at 1-m above ground (cm3)
• k is linear regression intercept while a, b and c are coefficients

Where:

• G0 is girth at base of pseudostem (cm)
• G1is girth at 100 cm above ground level (cm)

International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org

Across regions in Uganda APPLICATION OF ALLOMETRIC FUNCTION Across cultivars in Uganda

International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org

LIMITING FACTORS AND YIELD GAPS

• Each farm was visited once in 4

to 6 weeks

• Input data for the allometric

function were collected on flowered plants

• Agronomic management/crop

environment, pest damage data were also collected

• Boundary line analysis

identify the limiting factor/s and to quantify the yield gap due to each factor

International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org

LIMITING FACTORS AND YIELD GAPS

International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org

LIMITING FACTORS AND YIELD GAPS

International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org

• Evaluation of yield-determining factors during plant growth,

and

• Non-destructive estimation of bunch weights based on

allometry permit:  Identification of limiting factors  Quantification of yield-gap CONCLUSIONS