Variability in ridge and furrow size and shape and maize population density on small subsistence farms in Malawi

Tie-ridging is being promoted in Malawi as an on-field rainwater harvesting technique to reduce drought risk to a maize (Zea mays L.) crop. Adoption of tie-ridging often requires changes in farmers' tillage and crop practices. To ensure success, there is need to study farmers' current tillage and crop practices. Ridge and furrow sizes and shapes and plant population density were measured in 99 maize fields in four districts of the Central Region of Malawi in January 1997. The majority of farmers in Central Malawi did not follow government extension recommendations on ridge sizes (spacing, height and base width), within-row maize station spacing (maize spacing) and plant population density. Both ridge and maize spacing had a low coefficient of variation (CV<10%), while ridge base width and ridge height had the highest variability (CV>30%). The CV for number of plants per station was between 10% and 14%. The most common ridge shape was hemispherical and the next most common was triangular. Slope along the furrows was close to the zero slope of the contour ridge. Farmers compensated for different ridge spacing by varying the maize spacing and number of plants per station. Maize plant densities 30-50 days after planting were 6-40% higher and not lower than recommended plant density of 3.7 plants m(-2) (range 3.9-5.2 plants m(-2)). There is need to establish the negative impact, if any, of higher maize population densities on yield. (C) 1999 Elsevier Science B.V. All rights reserved.