A study was conducted in Bukoba, Missenyi and Biharamulo districts in the Kagera region Tanzania during the 2018/19 and 2019/20 cropping seasons to determine the effect of tillage methods, farmyard manure (FYM) and potassium (K) rates on cassava yield and root quality. Three tillage methods (flat tillage, tied ridging and open ridging), eleven fertilizer rates (FYM at 4 or 8 MT ha-1, N40P30 + K at 40, 80 or 120 kg ha-1, FYM at 4 or 8 MT ha-1 + K at 40, 80 or 120 kg ha-1) and the control, were arranged in Randomized Complete Block Design (RCBD) with three replications, using a split-plot design. Tillage methods were the main plots and fertilizer rates were the subplots. The plot size was 6 m x 5 m with a spacing of 1 m x 1 m. Root yield ha-1 was collected during harvesting and about 500 g of cassava roots from each treatment were oven-dried at 105 oC to constant weight for determining dry matter content using the equation by [31]. Root starch content in each treatment was determined using the method by [32]. The results indicate that cassava planted on ridges gave significantly (P <.001) higher cassava root yields (18.98 - 34.84 MT ha-1) than flat tillage (16.86 - 29.74 MT ha-1). The combined use of FYM at 4 MT ha-1 or FYM at 8 MT ha-1 and potassium fertilizer at 40, 80 or 120 kg K ha-1 significantly (P <.001) increased cassava root yield (14.56 - 39.94 MT ha-1) as compared to other fertilizer rates (8.90 – 29.63 MT ha-1). In addition, the combined use of inorganic N40P30K120 or the combined use of FYM at 8 MT ha-1 and potassium fertilizer at 80 or 120 kg K ha-1 gave significantly (P <.001) higher starch (28. 04 - 34.06 %) and dry matter (39.57 - 44.93 %) content in cassava roots than other fertilizer rates. Therefore, planting cassava on ridges and the combined use of FYM at 4 MT ha-1 and potassium fertilizer at 40, 80 or 120 kg K ha-1 is desirable for increasing cassava root yield. Moreover, the combined use of inorganic N40P30K120 fertilizers or the combined use of FYM at 8 MT ha-1 and potassium fertilizer at 80 or 120 kg K ha-1 is desirable for increasing the content of starch and dry matter in cassava roots.

A study was conducted in Bukoba, Missenyi and Biharamulo Districts, Tanzania with the objectives of characterizing, classifying and assessing the suitability of the study area for cassava production. A reconnaissance field survey using transect walks and auger observations was done in the study sites, which were geo-referenced in terms of international coordinates using Global Positioning System. Soil profiles representative of the study sites were excavated and named as MARU-P1, MISSE-P1 and BIHA-P1 for Bukoba, Missenyi and Biharamulo Districts, respectively. Soil profile description and data on the morphological features of the representative soils were collected according to the FAO Guidelines for Soil Description. Disturbed and undisturbed soil samples were collected from genetic soil horizons, processed and analyzed in a soil laboratory. Data on site characteristics, climate, soil morphological features and soil physical and chemical properties were used to classify the soils to the family level of the USDA Soil Taxonomy and to tier-2 of the FAO World Reference Base for Soil Resources. Soil suitability assessment of the experimental sites was done using a simple limitation method based on the FAO Framework for Land Evaluation. The results reveal that Pedons MARU-P1 and BIHA-P1 have similar morphological properties, which are different from pedon MISSE-P1. However, the studied pedons differ in their physical and chemical properties, implying differences in their use and management. The climate of the study sites is semi-humid with Udic soil moisture regime, which is generally favourable for crop production. According to the USDA Soil Taxonomy, pedons MARU-P1 and BIHA-P1 were classified as "Typic Kandiudults". In addition, according to FAO World Reference Base for Soil Resources, pedons MARU-P1 and BIHA-P1 were classified as "Haplic Ferralic Acrisols" and "Chromic Ferralic Acrisols", respectively. Pedon MISSE-P1 was classified as "Typic Endoaquolls" according to USDA Soil Taxonomy and as "Fluvic Gleyic Phaeozems" according to FAO World Reference Base for Soil Resources. Pedons MISSE-P1 and BIHA-P1 were both evaluated as marginally suitable while MARU-P1 pedon was evaluated as moderately suitable for cassava production due to soil fertility constraints. We recommended specific soil fertility management strategies in each studied site for optimum cassava yields.

A study was conducted in Bukoba, Missenyi and Biharamulo districts, Tanzania for the objective of determining the effect of tillage methods, farmyard manure (FYM) and potassium rates on soil pH and the concentrations of N, P and K in the soils and cassava leaves. The treatments were arranged in the Randomized Complete Block Design (RCBD) using the split-plot design with three replications. Tillage methods (flat tillage, open ridging and tied ridging), were the main plots, and the fertilizer rates [farmyard manure (FYM) alone at 4 MT ha-1 alone or FYM alone at 8 MT 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 alone at 4 MT ha-1 or FYM alone 8 MT ha-1 + potassium at 40, 80 or 120 kg K ha-1] and the control, were the sub-plots. The inherent and post-harvest composite soil samples for determining soil pH and the concentration of N, P and K in each site were collected, processed and analysed. Post-harvest soil samples and cassava leaf samples were collected from the control plots and plots that received the combination of FYM at 8 MT ha-1 and potassium at 40 or 120 kg K ha-1 during the second cropping season. The leaf samples were oven dried at 70oC, grounded to pass through 0.5 mm sieve and analyzed. The results indicate that there was no a significant (P = .05) difference in the soil pH and the concentrations of N, P and K in the soils and cassava leaves among the tillage methods. There was a significant (P < .001) difference in the soil pH and the concentrations of N, P and K in the soils and cassava leaves between the control and the combined use of FYM and potassium rates. However, there was no a significant (P =.05) difference in the concentrations of  N, P and K in the soils among the combined use of FYM and potassium rates, but there was a significant (P < .001) difference in the concentrations of N and K in cassava leaves among the combined use of FYM and potassium rates. The combined use of FYM at 8 MT ha-1 and potassium at 40 kg K ha-1, and the combined use of  FYM at 8 MT ha-1 and potassium at 120 kg K ha-1 significantly (P < .01) increased the soil pH and the concentration of N and K in the soil. However, the combined use of farmyard manure at 8 MT ha-1 and potassium at 120 kg K ha-1 gave significantly (P < .001) higher concentrations of N and K in cassava leaves than the combined use of farmyard manure at 8 MT ha-1 and potassium at 40 kg K ha-1. Therefore, combined use of farmyard manure at 8 MT ha-1 and potassium at 120 kg K ha-1 is desirable for increasing the concentration of N and K in the soil and in cassava leaves. However, for the resource-poor farmers who cannot afford the high rate of K, the combined use of farmyard manure at 8 MT ha-1 and potassium at 40 kg K ha-1 could be used.

No abstract

The resolution of using or not using a particular technology in crop production is governed by the profitability of that technology being used. A study was conducted in Bukoba, Missenyi and Biharamulo districts in the Kagera region during the 2018/19 and 2019/20 cropping seasons to determine the economic benefit of using different rates of farmyard manure (FYM) and potassium (K) fertilizer in cassava production. One village potential for cassava production was selected in each district for establishment of cassava trials. Three tillage methods [flat tillage, tied ridging and open ridging] and eleven fertilizer rates [FYM at 4 or 8 MT ha-1, N40P30 + K at 40, 80 or 120 kg ha-1, FYM at 4 or 8 MT ha-1 + K at 40, 80 or 120 kg ha-1] and the control, were arranged in a Randomized Complete Block Design (RCBD) with three replications using a split-plot design. Tillage methods were the main plots and fertilizer rates were the subplots. Cassava yields (MT ha-1) were collected at harvesting (12 months after planting). Partial budget analysis was carried out to estimate the gross values using the adjusted yields at market price for cassava and fertilizers. Costs and benefits were calculated on a hectare basis, in Tanzania Shillings (TShs) ha-1, and converted to USD ha-1 based on the prevailing exchange rate of 1 USD, equivalent to 2 300 TShs. All variable costs were summed up to total variable cost (TVC). The net benefits (NB) [gross benefit (GB) - TVC] ha-1 of the tested treatments were calculated and used to assess the profitability of each treatment. Moreover, the benefit-cost ratios (BCR) [net benefit ÷ TVC] of the tested treatments were compared to the acceptable value of greater than 2 for the technology to be adopted by farmers. The results indicated that in both cropping seasons, and in all studied sites, all the tested fertilizer types and rates gave acceptable BCR of greater than 2, implying that all the fertilizer types and rates could be used for cassava production in the study area. The results on net benefit indicated that the combined use of FYM at 8 MT ha-1 and potassium fertilizer at 80 kg K ha-1 gave higher net benefit (3 020 500 – 9 168 000 TShs ha-1 (1 313.3 – 3 986.1 USD ha-1) than the other fertilizer types and rates (1 915 000 – 9 024 500 (832.6 – 3 923.7 USD ha-1) and is therefore, desirable for increasing cassava root yield and net benefit. However, for the resource-poor farmers, the combined use of farmyard manure at 8 MT ha-1 and potassium fertilizer at 40 kg K ha-1 can still be adopted because, for some reason, not all the famers can afford the best treatment.