Cassava Growth and Biomass Yield Influenced by Land Cultivation Methods, Farmyard Manure and Potassium Fertilizer in the North-Western Part of Tanzania

Field trials were laid out in the north-western part of Tanzania to find out the effluence of land cultivation methods, farmyard manure (FYM) and potassium (K) rates on the growth and biomass yield of cassava using Randomized Complete Block Design (RCBD) and the treatments arranged in the split-plot design. The treatments were replicated three times. Three land cultivation methods, namely flat cultivation, open ridge and tie ridge were the main plots and; fertilizer rates including farmyard manure (FYM) alone at 4 t ha-1 or FYM alone at 8 t ha-1, nitrogen (40 kg N ha-1) + phosphorus (30 kg P ha-1) + potassium at 40, 80 or 120 kg K ha-1, and the combination of FYM at 4 or 8 t ha-1 + potassium at 40, 80 or 120 kg K ha-1 with no fertilizer treatment were the sub-plots. The FYM was applied during planting and the other fertilizers were applied at one month after planting and at three months after planting. Data on vigour (1-5), height of the plant (cm), number of branches plant-1, stem diameter (mm) and biomass (t ha-1) were collected at 12 months after planting. The results showed that planting cassava on the ridges improved growth and increased biomass as compared to planting on flat cultivated land. The combination of FYM at 4 t ha-1 or FYM at 8 t ha-1 and potassium at 40, 80 or 120 kg K ha-1, improved growth and offered significantly (P < .001) higher biomass (9.36 - 32.86 t ha-1) than the application of FYM alone at 4 t ha-1 (7.56 - 16.79 t ha-1), FYM alone at 8 t ha-1 (7.93 - 18.85t ha-1) or the application of N, P and K fertilizers (7.56 - 24.03 t ha-1). The interaction between land cultivation methods against the combination of FYM at 8 t ha-1 + potassium at 40, 80 or 120 kg K ha-1 improved growth and increased biomass (8.38 - 38.39 t ha-1) than the interaction between land cultivation methods against the application of FYM alone at 4 8 t ha-1 (5.24 - 23.39 t ha-1), FYM alone at 8 t ha-1 (5.57 - 25.37 t ha-1) or the combination of inorganic N40P30 + K at 40, 80 or 120 kg ha-1 (6.12 - 26.48 t ha-1). Thus, planting cassava on the ridges together with the combination of FYM at 4 t ha-1 and potassium at 40, 80 or 12 kg K ha-1 is recommended for the production of cassava in the study area.