Cassava Yield Research Articles

Crop Calendar Shift as a Climate Change Adaptation Solution for Cassava Cultivation Area of Binh Thuan Province, Vietnam.

Binh Thuan Province is one of the large cassava cultivation areas in Vietnam. However, in recent years the cassava crops are facing the increased risks of irrigation water shortage due to drought and abnormal change of rainfall under the impacts of climate variability (ICV), leading to reduce crop yield. The study was, therefore, conducted to define a suitable period for planting cassava crops in Binh Thuan Province, Vietnam to reduce the negative impacts of weather factors. The study was conducted using the AquaCrop model to predict the cassava yield corresponding to different crop calendars to define the suitable planting period. The model performance was appraised through the calibration and validation process with the index of agreement (d), correlation coefficient (r) up to 0.80 and RMSE lower than 0.40. The results carry out that the cassava yield can be reached 48.18 t ha-1 if the crop calendar (CC) is early shifted from 14-21 days compared with the current crop calendar (CCC) for spring crop while an increase of approximately 5.16% can be achieved if the CC is delayed from 7-14 days for summer crop season. The results stated that the proposed model is suitable for defining the CC based on its simulated biomass and cassava yield. The study indicated that rainfall plays an important role in the planting calendar of cassava crops. Through, it is also confirmed that planting calendars of cassava crops is not appropriate for current weather conditions.

Genome-wide identification of miRNAs targets involved in cold response in cassava

MicroRNAs (miRNAs) are recognized as essential transcriptional or post-transcriptional regulators, and play versatile roles in plants growth, development and stress responses. Cassava (Manihot esculenta) is a major root crop widely grown worldwide. Cold stress seriously affects cassava plants growth, development and yield. MiRNAs and their targets have been extensively studied in model plants, but a genome-wide identification of miRNAs’ targets is still lacking in cassava. In this study, two degradome libraries were constructed using cold-treated and control cassava seedlings to identify the roles of miRNAs and their targets in response to cold stress. Following high-throughput sequencing and comparing with miRNA database, degradome data allowed us to identify a total of 151 non-redundant miRNA-target pairs. We revealed that ~ 42% of miRNA targets are conserved across plant species. However, 83 novel miRNA targets were identified in the two libraries. Gene ontology analyses showed that many target genes involved in cellular and metabolic process. In addition, 12 miRNAs and 31 corresponding targets of them were further found to be involved in cold stress response. Particularly, miR159, 164 and 396 participated in cold stress response by up-regulating certain transcription factors that were involved in the regulation of downstream gene expression. The work helps identifing cold-responsive miRNA targets in cassava and increases the number of novel targets involved in cold stress response. Furthermore, the findings of this study might provide valuable reference and new insights for understanding the functions of miRNA in stress response in plants.

Towards closing cassava yield gap in West Africa: Agronomic efficiency and storage root yield responses to NPK fertilizers

Nutrient management of cassava has received little attention compared with cereal crops. We evaluated cassava yield potential and nutrient use efficiency when supplied with nitrogen, phosphorus and potassium at high rates and when supplied with increasing rates of K. On-farm experiments were conducted at six locations in Nigeria across the major cassava growing agro-ecologies of Western Africa (Tropical Rainforest – Cross River, Forest Transition Savanna – Edo, and Guinea Savanna – Benue) during two seasons (2016–2017 and 2017–2018). Nitrogen, P and K fertilizers were applied at various rates, including treatments with and without added secondary and micronutrients. Storage root dry matter (DM) yields ranged between 11 and 35 t DM ha−1. The largest yields were obtained with a mean agronomic efficiency of 60, 162 and 51 kg DM of storage roots per kg of N, P and K applied, with average uptakes of 364, 44 and 242 kg N, P and K ha−1 respectively. Storage root yield responses to applied N, P and K fertilizers (2–18, 3–16 and 3–22 t DM ha−1, respectively) varied across the locations, reflecting variability in potential yields and applied NPK ratios. Addition of a mixture of secondary and micronutrients did not affect cassava yields. We found that the caloric energy yield of cassava per kg of N applied is 2.7 times larger than the value reported for maize. Increasing the supply of K gave a high agronomic efficiency of N even when supplied at high rates, supporting the theory of “increasing returns to scale” of De Wit. We conclude that cassava has a major role in future food security of sub-Saharan Africa, with potentially larger DM yields, a better recovery of applied nutrients and larger energy yield per kg of applied N fertilizer when compared with grains.

A combined cellulosic and starchy ethanol and biomethane production with stillage recycle and respective cost analysis

To minimize waste generation in ethanol production from starchy and cellulosic feedstocks, the feasibility of stillage recycle to fermentation process was studied. For sugarcane bagasse (SCB) and palm empty fruit bunch (EFB), optimal hot-compressed water (HCW) pretreatment and enzyme hydrolysis (10% wt) gave the highest total reducing sugar (TRS) yields of 64.2% and 67.3%, respectively. Ethanol fermentation of SCB, EFB and fresh cassava by Saccharomyces cerevisiae TISTR5606 gave the highest yields of 0.31 g g−1, 0.40 g g−1, and 0.31 g g−1 TRS, respectively. For recycling of SCB and EFB stillage, a slight decline of ethanol yield was found while ethanol yield of cassava significantly increased from 60.8% to 89.9%. The ethanol yields from the 2nd recycle of cassava was still 10% higher than no recycle. Addition of 10%–20% v/v black liquor from lignocellulosic HCW pretreatment into anaerobic digestion system noticeably enhanced the chemical oxygen demand removal and methane production. Analysis of variable operating cost showed that stillage recycles for 20% for fresh cassava and 10% for SCB is cost-effective process for ethanol production.

Effect of Time of Harvesting and Disease Resistance in Reducing Cassava (Manihot esculenta Crantz) Yield Losses by Two Viral Diseases

Cassava mosaic disease (CMD) and cassava brown streak disease (CBSD) are two important biotic constraints for cassava (Manihot esculenta Crantz) production in Eastern and Southern Africa. CMD causes a general decline in yield in affected plants of susceptible cassava varieties but CBSD causes rotting of edible roots.

Screening of diverse cassava genotypes based on nitrogen uptake efficiency and yield

As one of the top three tuber crops of the world, cassava is a staple food and feed crop for tropical and subtropical regions. Because of its high drought resistance and tolerance to nutrient deficiency, cassava is usually cultivated on hilly areas that are nutrient-poor. Nitrogen (N) is one of the significant factors affecting cassava yield. A double factorial (N level×genotypes) split-plot field experiment was conducted to analyze differences in yield and N accumulation of 25 cassava genotypes under low-N conditions to screen for cassava genotypes with high-N efficiency. The two-year field experiment showed that cassava yield and N accumulation are determined by specific genotypes, soil N levels, and year. Among these factors, soil N levels are the main factors that are responsible for differences in cassava yield. When yield and relative N accumulation under low-N conditions were used as screening markers, we identified an efficient and responsive genotype (SC10), and two inefficient and non-responsive genotypes (SC205 and GR5). The efficient and responsive genotype and the inefficient and non-responsive genotype can be used as study materials to further reveal the mechanisms for high-N efficiency in cassava.

SOIL LOSS AND CASSAVA YIELD UNDER RIDGE TILLAGE IN HUMID TROPICAL CLIMATE OF SUMATERA, INDONESIA

Erosion is one of problem threatens the soil resource caused soil degradation. Applying the ridges system and organic fertilizer contributes to suppressing runoff and erosion. This study aims to determine the effect of applying different ridges system and the organic fertilizer on the runoff, soil erosion, nutrients loss of soil, nutrient enrichment ratio, starch content, growth, and yield of cassava on 12.5% slope land. The research was conducted at the field experiment, University of Lampung, under a humid tropical climate. This study used a Randomized Complete Block Design, which was arranged factorially with two factors, ridges system and organic fertilizer (organonitrofos) and four replications. Factor one is consists of G1 (ridges in the same direction with the slope) and G2 (ridges in the opposite direction with the slope), while factor two is consists of P0 (Organonitrofos 0 tons/ha) and P1 (Orgononitrofos 20 tons/ha). The results showed that the application of the ridges in the opposite direction with the slope significantly reduces the runoff 42.63%, soil erosion 61.68%, and suppress nutrient loss of N-total by 61.85%, P-available by 57.92%, K-total by 80.41% and C-organic by 61.22%, compared to ridges in the same direction with the slope. However, ridges systems do not give a significant difference to starch content, growth, and cassava yield. Physical obstacles formed by ridges in the opposite direction with the slope will force water to infiltrate into the soil so that the runoff rate, erosion, and nutrients loss can be reduced significantly. In reverse, the organic fertilizers do not affect all variables. The ridges system and the organic fertilizer did not significantly affect the starch content, growth, and yield of cassava. That caused by the application of synthetic fertilizers at the same dose (standard dose for planting cassava) in each experimental unit that fertilizer already enough to grow optimally.

Leaf area development and yield of cassava in response to pruning of shoots and the late supply of nitrogen and potassium

AbstractThis study evaluated leaf area development, leaf nutritional content, and yield of pruned/unpruned cassava supplied with nitrogen (N) and potassium (K) during its second vegetative cycle. Two field experiments were conducted in a randomized complete‐block design with split‐plots and four replications. The treatments consisted of four management approaches that combined pruning/not pruning with or without K as the main plot and four N application rates (0, 50, 100, and 200 kg ha−1 N) as the subplots. The results revealed that an evaluation of the nutritional status of cassava during its second vegetative cycle should be considered if shoot pruning has been conducted because pruned plants had higher concentrations of N, P, and K in their leaves, and unpruned plants exhibited leaves with higher Ca, Fe, and Mn concentrations. Pruning of cassava shoots during the autumn/winter resting phase did not negatively affect root yield and may represent a recommended management practice for cassava cultivation. In soils with a medium level of K availability, K provision during the second cassava growth cycle is unnecessary because the application of K did not increase leaf reconstitution or yield components in either pruned or unpruned plants. The late application of N improved the nutritional status of cassava plants and increased their leaf area during the second growth cycle. Cassava root, starch, and flour yields increased in a linear fashion in response to the late application of N.

Importance of genetic parameters and uncertainty of MANIHOT, a new mechanistic cassava simulation model.

We identified the most sensitive genotype-specific parameters (GSPs) and their contribution to the uncertainty of the MANIHOT simulation model. We applied a global sensitivity and uncertainty analysis (GSUA) of the GSPs to the simulation outputs for the cassava development, growth, and yield in contrasting environments. We compared enhanced Sampling for Uniformity, a qualitative screening method new to crop simulation modeling, and Sobol, a quantitative, variance-based method. About 80% of the GSPs contributed to most of the variation in maximum leaf area index (LAI), yield, and aboveground biomass at harvest. Relative importance of the GSPs varied between warm and cool temperatures but did not differ between rainfed and no water limitation conditions. Interactions between GSPs explained 20% of the variance in simulated outputs. Overall, the most important GSPs were individual node weight, radiation use efficiency, and maximum individual leaf area. Base temperature for leaf development was more important for cool compared to warm temperatures. Parameter uncertainty had a substantial impact on model predictions in MANIHOT simulations, with the uncertainty 2-5 times larger for warm compared to cool temperatures. Identification of important GSPs provides an objective way to determine the processes of a simulation model that are critical versus those that have little relevance.

Is Cassava (Manihot esculenta Crantz) a Climate “Smart” Crop? A Review in the Context of Bridging Future Food Demand Gap

Climate change and its impact on agriculture are one of the ongoing research areas, and the major task among agricultural managers is to meet the food demand in the future in the context of the production gap of major food grain crops. Literature analysis is carried out to understand the climate resilience of cassava, one of the major tuber crops and is considered to bridge the food demand gap in the near future. Systematic analysis of literature includes influence of changing environmental parameters such as temperature, solar radiation, photoperiod, air humidity, soil water deficit, salinity, elevated ozone and CO2, combined effects of elevated CO2 with temperature, water deficit and salinity to the growth and yield of cassava along with its resilience to biotic stresses and its climate suitability. Studies indicate cassava can tolerate a temperature level of up to 40 °C, and thereafter the rate of photosynthesis decreases. Cassava can be cultivated in regions with variations in solar radiation without much compromise in its yield in the context of global dimming of sunshine duration. The resilience to water stress and air humidity variations are adapted by reducing stomatal conductance without influencing the rate of photosynthesis. Cassava has also an inbuilt mechanism to cope with water scarcity by leaf drooping. Already established cassava can tolerate a salinity level of up to 150 mM and the younger ones can tolerate up to a level of 40 mM. Studies also indicate a strong positive influence of elevated CO2 of up to 700 ppm on the rate of photosynthesis and yield of cassava. Elevated CO2 enhances the resilience of cassava to water stress and salinity. Similarly, the combined effect of elevated CO2 and higher temperatures also increases the yield attributes of cassava. These all indicate the resilience of cassava to the changing climate and it ensures as an insurance crop as well as food security crop in the near future. Studies show its resilience to biotic stresses as well. Climate suitability studies also show its suitability in the present locations in the near future as well as its adaptation to other areas. However, the research gap is identified in areas of influence of elevated ozone on growth characteristics of cassava. This study also recommends identifying the extent of tolerance level of cassava to the influence of the combined effect of salinity and elevated CO2. Further, researchers need to concentrate on developing biotic as well as abiotic stress-tolerant genes in cassava varieties to increase its production irrespective of the changing climatic conditions.

Growth Response of Cassava to Deficit Irrigation and Potassium Fertigation during the Early Growth Phase

Cassava (Manihot esculenta Crantz) experiences intermittent water deficit and suffers from potassium (K) deficiency that seriously constrains its yield in the tropics. Currently, the interaction effect between deficit irrigation and K fertigation on growth and yield of cassava is unknown, especially during the early growth phase. Therefore, pot experiments were conducted under controlled greenhouse conditions using cassava cuttings. Treatments initiated at 30 days after planting included three irrigation doses (30%, 60%, 100% pot capacity) and five K (0.01, 1, 4, 16, and 32 mM) concentrations. The plants were harvested 90 days after planting. Decreasing irrigation dose to 30% together with 16 mM K lowered the leaf water potential by 69%, leaf osmotic potential by 41%, photosynthesis by 35%, stomatal conductance by 41%, water usage by 50%, leaf area by 17%, and whole-plant dry mass by 41%, compared with full-irrigated plants. Lowering the K concentration below 16 mM reduced the values further. Notably, growth and yield were decreased the least compared with optimal, when irrigation dose was decreased to 60% together with 16 mM K. The results demonstrate that deficit irrigation strategies could be utilized to develop management practices to improve cassava productivity by means of K fertigation under low moisture conditions.

Screening preemergence herbicides for weed control in cassava

AbstractWeed competition severely constrains cassava root yield in sub-Saharan Africa; thus, good weed control measures, including the use of herbicides, are increasingly important. Herbicide trials were conducted at five locations across eastern, western, and north-central Nigeria over two cropping seasons (2014 and 2015). Nineteen premixed PRE herbicides applied at different rates were evaluated for efficacy on weeds and selectivity on cassava. Manual hoe-weeding at 4, 8, and 12 wk after planting (WAP) and two S-metolachlor + atrazine treatments commonly used by cassava growers were included for comparison. Six of the 19 PRE herbicide treatments (indaziflam + isoxaflutole, indaziflam + metribuzin, flumioxazin + pyroxasulfone, isoxaflutole, acetochlor + atrazine + terbuthylazine, and terbuthylazine + S-metolachlor) consistently provided 80% to 98% broadleaf and grass weed control up to 8 wk after treatment. Overall, PRE herbicide treatments and cassava yield were significantly positively correlated. Herbicide treatments terbuthylazine + S-metolachlor, flumioxazin + pyroxasulfone, diflufenican + flufenacet + flurtamone (respectively, 60 + 60 + 60, 120 + 120 + 120, 90 + 360 + 120, and 135 + 360 + 180 g ha−1), acetochlor + atrazine + terbuthylazine (875 + 875 + 875 g ha−1), S-metolachlor + atrazine (870 + 1,110 g ha−1), oxyfluorfen (240 g ha−1), indaziflam + isoxaflutole (75 + 225 g ha−1), indaziflam + metribuzin (75 + 960 g ha−1), and aclonifen + isoxaflutole (500 + 75 g ha−1) contributed to yields exceeding twice the Nigerian national average of 8.76 tonnes ha−1. These treatments had root yields of 1.4 to 2 times higher than plots that had been hoe-weeded three times. There were some adverse herbicide treatment effects such as delayed cassava sprouting and temporary leaf bleaching observed in indaziflam and diflufenican + flufenacet + flurtamone treatments, whereas sulfentrazone caused prolonged leaf crinkling. The PRE applications alone at rates safe for cassava did not provide adequate season-long weed control; supplemental POST weed control is needed about 10 WAP for satisfactory season-long control.

Effects of limestone and organic fertilizer on cassava yield and on chemical and physical soil properties

ABSTRACT Cassava has a high yield potential that can be achieved with adequate liming and fertilization of the soil. The objective of this study was to evaluate the effect of organic fertilizer application, in association or not with liming, on yield and morphological characteristics of cassava roots and on chemical and physical properties of the soil. The experiment was arranged in the split plot design. The plots corresponded to limestone rates (0 and 2.5 t ha-1) and the sub-plots to chicken manure rates (0, 4, 8, and 12 t ha-1). Yield showed no response to limestone application, but responded to manure, producing 43 t ha-1 of roots at the rate of 8 t ha-1. The treatments had no influence on soil density and total porosity. The addition of manure increased the concentrations of P and K, while the addition of limestone increased Ca and Mg in the soil. The pH was affected only by limestone. Therefore, limestone does not affect crop yield and soil physical properties up to the amount used. Use of chicken manure up to 8 t ha-1 increased yield. Limestone and manure affect soil fertility in different ways.

Towards narrowing the cassava yield gap.

This article is a Commentary on De Souza et al. (2020), 225: 2498–2512.

Agro-Climato-Edaphic Zonation of Nigeria for a Cassava Cultivar using GIS-Based Analysis of Data from 1961 to 2017

To investigate the optimal cultivation conditions for cassava cultivar (TMS98/0505) in Nigeria, we employed agro-ecological zoning to delineate the cultivated lands. Using GIS-based multi-criteria analysis, we researched the influence of some meteorological and soil parameters on the clone cultivation. From the multiple-parameter climato-edaphic zoning map, an average yield of 26 t ha−1 was estimated. The dry Rainforest and southern Guinea Savanna account for 80% of the favorable zones. However, with irrigation, the cultivar would yield optimally in the northern marginal zones. Further, the significant climatic parameters are sunshine hour (t = 3.292, α = 0.0064) and rainfall (t = 2.100, α = 0.0575). Thus, the potentials of a location for cassava cultivation in Nigeria largely depend on the soil conditions, sunshine hour, and rainfall. Generally, the cassava yield correlates strongly (+0.88) with the suitability map. Considering future climate variability based on the annual rainfall data, we projected an average annual rainfall range of 565–3,193 mm between 2070 and 2099. Likewise, the projected range of daily temperature for 2046–2100 is 24.57–31.94 °C. Consequently, with currently allotted farmlands, Nigeria can double her current cassava production through soil fertility enhancement and irrigation.

Tillage and rice mill wastes mulch and their effects on soil properties and yield of cassava (Manihot spp.) on a Typic psamment at Abakaliliki, Southeastern Nigeria

The experiment was undertaken using cassava (Manihot spp) to evaluate effects of different tillage practices and mulching (raised mulched bed, raised not mulched bed, flat mulched bed, flat not mulched bed, untilled mulched bed and untilled not mulched bed) on soil properties and cassava sprouting and yield in 2016 and 2017 planting seasons on a Typic psamment in Ikwo, Ebonyi State, Southeastern Nigeria. The experimental study is made up of six treatments, arranged in randomized complete block design and replicated four times. The results indicated significantly (P<0.05) higher (28.18 – 27.16%) GMC in beds mulched than corresponding values (17.10 – 15.26% and 16.20 – 15.10%) obtained in untilled mulched and untilled not mulched beds for both seasons. Results showed that available P, N, Ca and Mg were respectively higher (P<0.05) in mulched raised beds when compared to those of untilled mulched or untilled not mulched beds by 31 – 28%, 32 – 71%, 50 – 33%, 50 – 30%, 89 – 67% and 49 – 26%, 91–71%. At 28 DAP for 2016 and 2017 planting seasons results showed that 90–78% of the planted cassava cuttings sprouted between 14 – 17 days earlier in both tilled mulched beds and tilled not mulched beds compared to untilled mulched or untilled not mulched beds (5 – 48%). These were (P<0.05) 40 – 50% and 47–37% significantly higher in tilled mulched and tilled not mulched beds when compared to untilled mulched and untilled not mulched beds. At harvest (300 DAP), highest cassava tuber yield (7.5–7.3t ha-1 ) were obtained in raised mulched beds for 2016 and 2017. Cassava yields were (p<0.05) higher in raised mulched beds by 60 and 59% compared to their counterparts in untilled not mulched beds for the seasons. These findings imply that rice mill wastes mulch provide a good and conducive soil condition for cassava than unmulched or untilled environment and raised mulched beds provide more robust condition for cassava production relative to other treatments tested in this study

Comparative Effects of Organic Cocoa Shell-Based and Inorganic NPK Fertilization on the Growth and Yield of Four Cassava Varieties

Looking of finding an alternative to the use of chemical fertilizers to increase yields of cassava (Manihot esculenta), trials were carried out in the Lamto zone in central Cote d’Ivoire. Thus, the effects of compost and ash from cocoa shell and NPK were tested on the agronomic parameters of cassava. The trial was conducted for two years with four varieties of cassava: Yace, Alleda agba, Six mois and Bonoua, grown on elementary plots treated with one of these fertilizers. The experimental design was complete randomized blocks with three replicates. Analysis of the results showed that the Six mois variety gave the longest stems (131, 67 cm) with the cocoa shell compost. The Bonoua variety, on the other hand, gave the largest diameter of the stem base (21.56 mm), a higher number of leaves (77.30) and a large wingspan (136.89 cm) with cocoa shell compost. The leaves developed by the plants of this variety were wider (19.30 cm) and longer (17.96 cm) with cocoa shell compost. Also, this Bonoua variety treated with shell compost yielded a high number of tuberized roots (5.11), high average weight per plant (5.83 kg/plant) and higher yield (58.29 t/ha). This compost of cocoa shell has also allowed a better conservation of the cultivated soils quality.

Physico-Chemical Soil Properties and Their Correlations with Maize and Cassava Production in Ebonyi, Nigeria

This study analyzed relationships between soil properties and food crop production in Ebonyi State of southeast Nigeria. Free survey was conducted after three zones (Agbaja, Akaeze and Ikwo) in the state were purposely selected for representation of the soil sampling. Two types of sampling were conducted; Auger sampling at 0 - 20 and 20 - 40 cm depths and soil profile sampling. Annual crop yield data on maize and cassava for the state from 1988 to 2017 were collected from Agriculture Development Program. Variations in properties among soil horizons were obtained using coefficient of variations while soil parameters were regressed against crop yields to establish their relationships. Results showed that fine sand, total sand, bulk density, total porosity, soil pH, and available phosphorus significantly (p = 0.05) differ from 0 - 20 cm and 20 - 40 cm depths. Also, cassava yield correlated negatively with base saturation, and organic matter at 0.05 probability level; with exchangeable Ca and Na at 0.01 probabilities level but correlated positively with bulk density and available water capacity at 0.01 and 0.05 probability levels, respectively. Similarly, maize yield correlated negatively with available phosphorus and total nitrogen at 0.05 probability level; and with total porosity and exchangeable Ca at 0.01 probability level; and then correlated positively with available water capacity, and bulk density, at 0.01 probability level; with coarse sand at 0.05 probability level. However, soils of Ebonyi State are fertile but some of the chemical properties are still low, therefore, it is paramount to improve the quality of the soil to achieve improved food security in the state.

Pedological Characterization and Suitability Assessment for Cassava Production in Bukoba, Missenyi and Biharamulo Districts, Tanzania

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 <i>Udic</i> 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 <i>“Typic Kandiudults”</i>. In addition, according to FAO World Reference Base for Soil Resources, pedons MARU-P1 and BIHA-P1 were classified as <i>“Haplic Ferralic Acrisols”</i> and <i>“Chromic Ferralic Acrisols”</i>, respectively. Pedon MISSE-P1 was classified as <i>“Typic Endoaquolls”</i> according to USDA Soil Taxonomy and as <i>“Fluvic Gleyic Phaeozems”</i> 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.

English

The objective of this study was to test for appropriate quantity of fertilizer (NPK 12-11-18) required to boost the production of cassava (variety TME 419) in the forest zone of Cameroon. The trial was conducted at the experimental farm of the Institute of Agricultural Research for Development (IRAD) in Mbalmayo. The experimental design was completely randomized block design in three replicates. The treatments were as follows: T0 (Control (No input)); T1 (200 kg.ha-1); T2 (300 kg.ha-1); and T3 (400 kgha-1). The data were analyzed using the IBM SPSS Statistics 20 Software. The results showed that chemical fertilizer improves the growth (number of leaves, plant height, and petiole length) and yield (number of marketable root, yield) of cassava mainly because it enhances soil nutrient availability. Thus, NPK-fertilizer significantly (p&lt;0.001) increased petiole length by 20.71, 27.83, and 31.62% for T1, T2, and T3, respectively at 5 months after planting (MAP). The highest plant height and number of leaves at 4 and 5 MAP was observed with T3 followed by T2 and T1. Similarly, the highest root yield (43.33&plusmn;10.97 t.ha-1) was observed with treatment T3. Hence, the fertilizer application rate of 400 kgha-1 of NPK 12-11-18 appears most appropriate for intensification of cassava production in the humid forest agro ecological zone of Cameroon. Key words: Cassava, growth, NPK, root yield, soil fertility. &nbsp