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Effets des biomasses vertes deE. G. BILONG et al. / Int. J. Biol. Chem. Sci. 11(4): 1716-1726 1717 Effects of Tithonia diversifolia green biomass and mineral fertilizer on the growth, development and yield of cassava (Manihot esculenta Crantz) in the forest zone of Cameroon ABSTRACT Improving the productivity of ferralitic soils in forest areas may be possible through local inputs in addition to mineral fertilization. The aim of this study was to evaluate the effect of green biomass of Tithonia diversifolia on the performance of cassava (Manihot esculenta Crantz) in the forest zone of Cameroon. The experiment was performed with a factorial design. The treatments in three replicates included two varieties (improved and local) and a single dose of Titonia diversifolia green biomass (6 tha -1 ) applied alone or in combination to 100 kg of 14-24-14 (NPK) mineral composite fertilizer + 5 (S +) +3.5 (MgO) and compared to controls without fertilization and with inorganic fertilizer alone. The results obtained showed that the use of Tithonia diversifolia green biomass as fertilizer is recommended because it favors development of cassava and increases yield. Plants treated with 6 t.ha-1 of Tithonia diversifolia green biomass combined with 100 kg of mineral fertilizer yielded 29.58 ± 0.42 t.ha -1 and 22.8 ± 4.36 t.ha -1 respectively for the improved and local variety, contrary to controls from which 17.4±4.34 t.ha -1 and 11.8±1.7 t.ha -1 were from improved and local variety respectively. The yield of plants treated with green biomass of Tithonia diversifolia combined mineral fertilizers significantly increased (P <0.01) by 11 t.ha -1 for the local variety and 12.8 t.ha -1 for the improved variety (about 48% for the local variety and 43% for the improved variety), compared to controls. Green biomass of Tithonia diversifolia can therefore be used as complement to mineral fertilizer for improvement of ferralitic soils productivity.

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The transportation load of oil palm ( Elaeis guineensis Jacq.) seedlings from the nursery to planting sites is a crucial problem facing the extension of smallholder plantations in Cameroon. This load can be considerably reduced by removing soil from the roots, which in turn exposes the plants to water and nutrients stresses. A greenhouse pot experiment was carried out to evaluate the recovery performance of such soil-stripped seedlings as a function of watering frequency and soil texture. Plant recovery potential was monitored on 360 nursery seedlings aged 4 months, under two soil types (sandy clay soil with 46% fine particles and sandy loam soil with 19% fine particles) and two watering frequencies (daily and two-days). Three monthly measurements were taken on morphological plant growth parameters including Plant height, Foliar surface, Collar diameter, Root length and Plant weight. Within and between groups analyses of variance and means separation showed the greatest variability for collar diameter, foliar surface and plant weight. All the parameters showed a greater variability and an almost-constant growth from one month to another, except for plant weight that did show a highly significant (p = 0.000) increase between the first measurement and the second. Soil type, watering and their interaction explained 97–99.5% of the variations of all parameters. Except for root length, all other parameters were more sensitive to the effect of soil texture, explaining 83–95% of the total variation. Only plant weight and root length showed slightly greater values under daily watering, other parameters did not show any sensibility to the two watering frequencies proposed in this experiment. Our results showed a low response of plant growth recovery on the low clay sandy loam soil, revealing that a careful selection of a soil texture is crucial for the survival of seedlings and further establishment of the plants following drought stress. It is therefore strongly recommended to many tropical countries where oil palm is an economically important crop, to take this into account during the selection of soil type for oil palm seedlings nursery.

Cassava cultivation causes serious soil fertility depletion in southern Cameroon due to high mining of soil nutrients by the crop. This study aimed to evaluate the effects of Tithonia diversifolia fresh biomass (TB), poultry manure (PM) and inorganic fertilizers (IF) on soil properties, cassava yield, and the economic returns. The treatments consisted of two rates of TB (10 and 20 t ha−1), two rates of PM (10 and 20 t ha−1), two rates of combined TB and PM (5 and 10 t ha−1), a single rate of inorganic fertilizers (100 N:22P:83 K kg ha−1) and a control. The results showed that soil properties, soil quality index and cassava yield were significantly improved by the application of the organic manures. Tithonia diversifolia fresh biomass (TB) and poultry manure (PM) lowered the soil bulk density, increased soil total porosity, water holding capacity and chemical properties. TB and PM, solely or mixed, improved the aerial dry biomass (ADB) and fresh tuber yield (FTY) of cassava. The organic manures performed better than inorganic fertilizer. The highest yield (51 and 52 t ha−1 of fresh tubers) was obtained with the mixture of TB and PM applied at 10 t ha−1 each for the successive years. Positive and significant correlation was found between SQI and cassava yield. TB and PM combined at 10 t ha−1 each was the most profitable and cost-effective treatment, with a good benefit:cost ratio of 3.2:1 and net return of FCFA 3.736.900 ha−1. Thus, the use of Tithonia diversifolia fresh biomass and poultry manure is a sustainable method for cassava production in the southern Cameroon.