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 o f tie-ridging often requires changes in farmers' tillage and crop practices . To ensure success, there is need to study farmers' current tillage and cr op practices. Ridge and furrow sizes and shapes and plant population densit y 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 no t follow government extension recommendations on ridge sizes (spacing, heig ht and base width), within-row maize station spacing (maize spacing) and pl ant population density. Both ridge and maize spacing had a low coefficient of variation (CV<10%), while ridge base width and ridge height had the high est variability (CV>30%). The CV for number of plants per station was betwe en 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 s lope 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 re commended plant density of 3.7 plants m(-2) (range 3.9-5.2 plants m(-2)). T here is need to establish the negative impact, if any, of higher maize popu lation densities on yield. (C) 1999 Elsevier Science B.V. All rights reserv ed.