J. Viola Glenn1, Dr. Oluyede Ajayi2, Dr. Fred Cubbage1, Natasha James1, Darlene Casstevens3

1 NC State University, Department of Forestry and Environmental Resources 2 World Agroforestry (ICRAF) 3 NC State University, Department of Economics

31% of GDP in agriculture sector

15.9 million in population

2.8% increase in 2010, 17th fastest growing country in the world

Malawi

Importance of Study

Fertilizer tree indigenous to Africa and Middle East which is intercropped with agricultural crops

Increases food crop yields by 280% in experimental setting

Additional benefits: fuelwood, fodder for livestock, shade, timber

Faidherbia albida

Methods and Data

Can maize yield increases observed in experimental settings be observed in actual farming operations, managed independently of researcher guidance?

Population Growth and Food Security

Unsustainable dependence on expensive chemical fertilizer and reductions in food crop

yield

Depletion of soil nutrients and reduction

in overall soil fertility and quality

Shorter rest, or fallow, periods

between the planting of food crops

Pressure on arable land

Rapid population growth

Research Question

Data Collection, 2011

Semi-formal household survey of 391

subsistence smallholder farmers 509 individual fields, 72% with F. albida Two districts in the Central Region (Ntcheu

and Salima) Random sample generated from

comprehensive lists provided by Agriculture Extension

Data collected on : planting and maintenance costs of maize and F. albida, soil, trees, use of other technologies, demographics, non-yield tree benefits and general adoption attitudes

Data collected immediately after maize harvest by local university students to foster accurate recall and minimize communication issues

Mean/ % Yes

Min Max

Yield per acre (kg) (y) 611 10 2,160 Tree Characteristics (x1 – x3) Presence of trees (=1 if there is at least 1 tree in field)

71%

Trees per acre 4 0 32 Average diameter of trees (inches)

10 0 52

Farm and Field Characteristics (x4 – x8) District Ntcheu = 0 (50%)

Salima = 1 (50%) Use of hybrid maize 54% Soil fertility Poor (21%) = 0

Average (48%) = 1 Good (31%) = 2

Mkanda soil (=1 if soil is dark clay)

66%

Use of chemical fertilizer (=1 if used)

87%

Farmer Characteristics (x9 – x13) Dwelling type (income proxy)

Mud brick (35%) = 0 Poles/straw (0%) = 0 Burned brick (65%) = 1

Age of head of household 46 18 93 Agroforestry experience (years)

11 0 51

Education level of head of household

None (13%) = 0 Primary School (not completed) (58%) = 1 Primary School (completed) (16%) = 2 Secondary school (11%) = 3 Post-secondary school (1%) = 4

Household type Husband and wife (77%) = 0 Single male (1%) = 0 Single female (22%) = 1

Summary of Key Variables

Results

Regression Coefficients

Model: y = f(xi) 3 Ordinary Least Squares models with

different independent variables (xi) to represent trees

Dependent variable (y) - maize yield / ac (kg) N = 491

1 2 3 Tree Characteristics Presence of trees 86.0*** Trees per acre 22.5*** Trees per acre, squared -0.6** Average diameter of trees (inches)

6.3***

Farm and Field Characteristics District (=1 if in Salima district)

71.7*** 82.2*** 92.9***

*Hybrid maize (=1 if field uses hybrid maize)

47.1* 45.9* 49.3*

Soil fertility 51.2*** 47.5** 60.8*** Mkanda soil (=1 if soil is dark/clayey)

61.0** 59.3** 48.5*

Farmer Characteristics Dwelling/income proxy (=1 if housing type is burned brick)

85.4*** 84.2*** 80.7***

Age (head of household) -2.6*** -2.4*** -2.9***

Adjusted R2 0.10 0.12 0.12

*** significant at 1% • ** significant at 5% • * significant at 10%

Conclusions

Each metric shows a significant positive relationship between yield and F. albida

Yield increase is 10% to 14%, at the mean (~78kg per acre), equivalent to Malawi government estimates of the amount of maize required to feed an adult for 3 to 4 months

(1) Trees are correlated with greater maize yields

(2) Environmental fixed effects and income are also important

Environmental fixed effects are captured in the District variable which includes all fixed variations between the two regions: altitude, climate, precipitation, soil moisture content, etc.

Type of dwelling is used as a proxy for income, with burned brick homes used as an indicator of relative wealth

Both variables have impacts similar to that of F. albida in magnitude and significance

Additional data are available on gender of respondent, number of household members

Further testing of methods for representing presence of trees may yield better fitting models, e.g. one which uses both diameter and density

Detailed financial assessment of cost of planting and maintaining F. albida

Caveats

Maize yield and field size data rely on farmer recall rather than direct measurement, though resulting distribution of yield per acre is relatively normal

Soil fertility status is also self-assessed using a quantitative scale, which limits the study’s ability to make causal connections between fertility and the presence of trees

Future Work

Acknowledgements

ICRAF (Dr. Oluyede Ajayi, Dr. Frank Place, Dr. Dennis Garrity, Dr. Tracy Beedy, Innocent Phiri, Maurice Zimba); NCSU (Dr. Fred Cubbage, the Laarman Grant, Natasha James, Darlene Casstevens, Dr. Melinda Morrill); USAID

o Reverse leaf phenology from crops o Nitrogen fixing o Roots improve soil structure