Effects of Filter Cake Fertilization On Soil Chemical Properties and Cassava (Maniho Esculenta Crantz) Yield In Swaziland

A field investigation was conducted in Swaziland in 2007-2008 cropping season to determine the effects of filter cake fertilization on soil chemical properties and cassava (Manihot esculenta Crantz) yield. The experimental design was a randomized complete block design, replicated four times. A factorial arrangement was used, with two varieties of cassava (ʹNyasaʹ and ʹLine 65ʹ) and five levels of soil amendment materials. The treatments were: control (no soil amendment), 20 t ha-1 of filter cake; 40 t ha-1 of filter cake; 60 t ha-1 of filter cake; and 300 kg ha ha-1 of mixed fertilizer, N:P:K. Results showed no significant differences in organic matter content (Nyasa, 5.1%; Line 65, 5.2%). Filter cake fertilization modified the soil pH (from the initial pH of 5.6) to: Nyasa, 5.8, Line 65, 6.0, indicating that Line 65 was better at reducing soil acidity. Total nitrogen (Nyasa, 0.171%; Line 65, 0.184%) was not significantly different in the soil. Line 65 yielded 50.1% higher tuber mass (2,893 kg ha-1) than Nyasa (1,443 kg ha-1). Filter cake had advantages on cassava production, the extent of the advantage depending on the cassava variety, and the amount of filter cake used. It is recommended that 60 t ha-1 filter cake could be applied to cassava; Line 65 is recommended as the preferred variety to plant under filter cake fertilization. Further research evaluating the impact of filter cake applications above 60 t ha-1 on cassava production and long-term studies to further elucidate the impact of filter cake on soil chemical properties are recommended.